Dave's Volvo Page - 4-Speed Mark VIII Cooling Fan Harness Project and Diagrams

2 4 0 T U R B O . C O M
D A V E ' S V O L V O P A G E

4-Speed Cooling Fan Controller
Project and Diagrams

UPDATED: January 12, 2024 CONTACT

D O M A I N S

4-Speed Cooling Fan Controller Project

THIS IS OLD INFO.

I NO LONGER USE THIS CONTROLLER, BUT I'LL LEAVE THIS PAGE UP FOR REFERENCE.
I am NOT offering anything for sale here. You may use this info for your own entertainment if you like.
Before I published this page I began a discussion at
forum discussion about this project, which you can find here.

INTRODUCTION

I began this project in summer 2016 out of frustration.
I had experienced successive failures of a number of ready made fan controllers over the years (Delta Current Control and Flexalite), partly because I was using a high-amp Ford fan. So this project gave me a challenge to see if I could build something BETTER on my own that would do TWO THINGS:

1. Outlast those damned fragile fan controllers.
2. Offer some decent improvements, such as a soft or slow speed start-up AND an independently adjustable AC fan speed.

This project became a nice success and I used it for a couple of years with flawless performance.

But then . . . . .

In 2018 I discovered this line of high-amp PWM fan controllers. So I tried one and then retired my home-made 4-speed controller.
This new controller was flawless for years until I tried something new again.
CLICK HERE TO SEE MY INSTALLATION OF THIS NEW PWM CONTROLLER.

HERE'S THE START OF MY HOME-MADE CONTROLLER BUILD

During the summer of 2016 I began looking into creating my own relay-based cooling fan controller after experiencing a succession of failures over the years other commercially available fan controllers, such as Delta Current Control (DCC) and Flex-a-lite.

All of these failures have brought me to the conclusion that variable speed fan controllers have some nice technology, but you should NOT expect MOST of them to be reliable for long if you're using a high current fan like the Lincoln Mark VIII. So I needed a better alternative.

My experience over many years has been that standard relays are reliable. So as long as you take reasonable care when building a high-current relay harness, it will last a long time.

<<< This was the last commercially available fan controller I used and it failed on me in 2016. That failure came really close to frying my engine. I switched to this Flex-A-Lite after the successive failures of TWO Delta Current Control (DCC) controllers one after the other.

<<< This is the Flex-A-Lite 33054 "Variable Speed Controller." It was rated at 45 amps and I originally bought it thinking it was a PWM controller, since they advertise it as a "soft start' controller. I was disappointed after I discovered that this controller actually acts as a 2-SPEED controller, NOT as a TRUE variable speed controller. It has 2 speeds: Low speed is 60% and high speed is 100%.

Most commercially available variable speed fan controllers on the market are not designed to handle the heavy loads that come with a fan like the Lincoln Mark VIII.

Hayden offers a PWM controller (PN 3655) that, when checking, is limited to only 30 amps. That's not enough for a big fan like the Lincoln, which draws 40 amps at a steady 100%.

Derale offers one (PN 16795) that claims to handle 65 amps, but their Amazon ratings show a lot of failures.

Proform offers a digital variable controller (PN 69596). Proform does not list an amp rating, but their instructions limit you to a 16 inch fan. You should know most fans that size don't pull far less than 30 amps, so they don't really make a fan controller work very hard.

What went wrong with DCC?

There are lots of people who love the Delta Current Control fan controllers. I loved them too once. Their line of PWM variable boxes are enticing in their web site and the cost is fairly reasonable. The problem I had was when TWO of them failed one after the other.
This was in my 240 (they lasted 1.5 to 2 years on average). At that time I was using an early '90s Ford T-Bird fan, which pulls lots of current (around 35 amps). I had the largest controller DCC offered at that time (65 amps) which was installed according to their specific instructions. DCC has steadily increased their advertised current capacity in their controllers over the years and as of this writing their most powerful one will supposedly handle 95 amps.

I can handle failures. I was even prepared to just buy another one.
What I WOULD NOT TOLERATE was my experience with DCC's NON-EXISTENT CUSTOMER SERVICE.
When the last DCC controller failed, I ordered another on their website and paid with Paypal. I received no acknowledgement of an order. No follow-up email. And as the of weeks went by I emailed the owner (Brian Baskin) a number of times. My car was down the entire time! After six weeks had gone by with nothing, I finally filed a Paypal dispute and eventually got my money back. I never heard from Baskin. What kind of business does crap like this? Not a place I ever want to deal with again. They offer a 90 day warranty, but what good is that if they NEVER ANSWER EMAILS?

They have the following statement in their site: "In a time when profit margins govern allowable failure rates, product features are determined by the opportunity of market exploitation, and the consumer is seen as no more than a short term item of commodity, the value put upon interim revenue is clear. We see things a bit different at Delta. We appreciate the value of our customers not as commodities, but as our best means of long term market expansion. There is no better advertisement than word of mouth."
Ha! I agree there's no better advertising than word of mouth and here's MY word!
I have seen a number of forum posts and received emails from other people who have had the same experiences as I had with them. I think I'll stay away from them.

Also, I've been disappointed that so many of the high-tech fan controllers offer ONLY threaded screw-in temp sensors designed to go into your engine (or maybe so you can have a custom bung welded in your radiator?). I know radiator fin probes don't have as good a reputation, but I've used them successfully for many, many years and they work pretty well when you can find a good position. Why don't more companies offer more options? Many do not.

While I'm registering complaints about options, I've also noticed that if you want a fan controller to increase to a higher speed when your AC comes on, the ONLY option seems to be 100%. Really? That seems really short-sighted. What if you want only 60, 70 or 80% instead of full speed for your AC? If you're going to the trouble of building a high-tech PWM controller, isn't that a simple extra to add? Maybe AC fan speed is not really an important thing to fan controller engineers.

So as you may have noticed, I'm using a Lincoln Mark VIII fan and shroud (1997 model) mounted on a large 26 inch wide Griffin aluminum radiator. I decided to try building my own fan controller using simple, reliable relays to see if I could make it work the way I wanted and I wanted one that would LAST.

There are people who will warn you that using relays is risky, since relays can be slowly damaged from turning on high-current motors over and over. This may be true, but It's my opinion that it would takes years and I doubt the damage would come anywhere close to having a high-tech controller meltdown every 1.5 to 2 years!

More general info on the installation of my Mark VIII fan and Griffin radiator in my Volvo 242 Turbo can be found in my Cooling Fan Project Page at:

https://www.240turbo.com/ElectricCoolingFans.html#markVIIIfan

Your feedback is appreciated.

If you have any questions or comments or if you decide to use this info to build something like this for yourself, I would like to hear from you.

CONTACT ME

NOTE: I used the first diagram below when completing this project. I have not tried the alternate diagram below that.
FOUR SPEED RELAY FAN CONTROL EXPLAINED
This setup works for any 1 or 2-speed cooling fan. If a 2-speed fan is used, I suggest using the high speed circuit on the fan. I opted for using multiple adjustable temperature probes as shown. The probes can be mounted onto or inserted into radiator fins or into a coolant hose for direct coolant contact. This allows you to custom set each speed setting to a precise temperature set point for your car. Starting and fan speed ramp-up is smooth when starting at a low speed.
Of course you may instead use any type of temp senders you like and mount them where you like, such as in the radiator, engine or hose, however I don't know of any others that are so simple AND ADJUSTABLE besides those I show below.

Diagram I used for my 4-speed configuration.

Here's the 4-Speed Successive Relay Function Theory

There are TWO different diagrams above. Either will perform the same function. You may refer to them as I explain how this is done below.

I designed this to allow the cooling fan to remain OFF until your low temp set point is reached and the sensor activates power to the low speed relay (Relay 4). Since this low speed circuit will only allow a low amperage current value, it starts the fan slowly and softly, without the heavy drag you would get normally from starting a high-current motor. This low speed can be used to maintain cooling at idle with minimum fan use, but this would depend on the fan speed chosen for the low speed. There are a few choices.

When your temperature climbs a little higher, the SECOND sensor will activate the next relay (Relay 3), automatically cutting power from the lower speed relay (Relay 4). This way only ONE CIRCUIT will be powering the fan at a time.

This successive function works for each relay to increase fan speed as temperatures rise.

Why Four Speeds?

I know two speeds is definitely not enough for a Mark VIII fan, because the full speed is serious overkill most of the time. Three speeds might be ok and the above diagram can easily be adjusted to make it into a 3-speed controller by simply eliminating relay #4. Four speeds just seemed about right to me. Heck, you can even build a 5-speed harness using these components by adding just one more relay. But I chose to do four speeds.

The amperage capacity for the high speed relay (Relay 1) will depend on the fan you use. Most 15 inch or smaller fans (such as those found in Volvo 960, 850, S80) can get by with a 40A relay for the high speed (however I suggest 50A). A larger fan, such as the 17-18 inch Ford Taurus/T-Bird/Lincoln Mark VIII fans, should use a 70 or 80A relay. These big fans can pull 35-40 amps continuously at full power, so power and ground cables for these fans should be fat, such as 8-10 gauge (AWG) or fatter. I'm using 8 gauge. 10 gauge would probably be fine.

The 8 and 10 GA cables I'm using for my project are high-flex fine strand type. Cables in 8 gauge and larger can usually be found sold as welding cable. I found them sold in reasonably short lengths on Amazon so you don't need to buy them in large spools. Fine strand cable has much finer strands than common automotive cable. I'm willing to pay a little extra because I've grown tired of dealing with stiff, large strand cable that's hard to form tight bends and then breaks easier after years of long-term vibration.

Maybe you don't think a big fat cable can snap from vibration. I found out when a 4 gauge alternator cable snapped off at the alternator lug after about 4 years of use, stranding me on a long trip.

Here's a wire gauge guide that you may find useful.

It shows minimum recommendations for wire size based on length of wire and current draw in amps.
If you pay close attention, you'll find I used larger cables than required. That's ok in my book. Just don't use smaller than minimum.

OPTIONAL AC RELAY (Relay #5):

This relay is not shown in the four speed diagram above. This optional relay will override all other relays (except for the full power relay operated by an override switch). Since my preference was NOT to use 100% speed for the AC, my idea was to wire this relay to the "HIGH" relay, which actually runs below full power (this turned out to be 77% in my case).

The 12V switched wire at terminal 85 gets connected to the power wire that activates your AC compressor.
NOTE: Or if you have an '84 to '89 Volvo 240 you may use the AC power 'ON' wire, which is the Red/White wire going to the AC microswitch (attached to the AC knob switch in the center dash).

Mini ISO Relays used for this project:
1. Full Power 100%: SPDT rated at 80 amps.
2. High: SPDT rated at 40 amps.
3. Medium: SPDT rated at 40 amps.
4. Low: SPDT or SPST rated at 40 amps.
5. AC: SPDT or SPST rated at 15 to 40 amps.

Mini ISO Relay Connections (View from bottom of relay or bottom of connector plug)
SPST (Single Pole, Single Throw): This type relay will have an 87b center pole.
SPDT (Single Pole, Double Throw): This type relay will have an 87a center pole. Also known as a changeover relay.
RELAY PINOUTS:
30: Constant 12V (battery), unswitched
85: Signal, 12V switched (fuse panel)
86: Ground (completes coil circuit to close connection)
87: Consumer 12V (to fan or other device to be powered)
87b: Extra consumer (same circuit as 87)
87a: Opposite of 87 (SPDT changeover relay only)

SPST vs SPDT Relays. What’s the difference?

Single Pole, Single Throw (SPST): This relay will be identified as having a middle 87b spade (or sometimes no middle spade at all). This is the most common relay used for fog lights or other simple circuits. If there is a middle 87b pin, that pin will have power whenever there is power to the 87 pin. This way the middle 87b pin may simply be used as an extra power output.

Single Pole, Double Throw (SPDT): If you have a relay with an 87a pin in the middle, it's an SPDT relay, also called a "changeover" relay. In a changeover relay, the 87a pin will be “HOT” anytime the 87 pin is "OFF," so long as the relay is connected to power. So when 87 is "OFF", 87a will be "ON". When 87 turns "ON", 87a will turn "OFF".

The Hayden 3653 adjustable temperature probe sensor pictured here can be purchased from Amazon or Summit Racing for about $20 each. It's only rated at 16 amps, so it really should not be used for a fan without a relay. This mechanical sensor may be used to trigger a 12V circuit or a ground circuit, either one. For my project I chose to have it complete ground circuits. The male terminals on the side are typical .250 inch (6.3 mm). According to Hayden, the temperature range is 32°F to 248°F (0°C to 120°C). Turning the trim pot CLOCKWISE increases the temperature set point; COUNTER-CLOCKWISE decreases it. The kit comes with a mounting bracket, some screws, some .250 inch insulated terminals, some wire and some mounting parts for the radiator probe.

I've noticed at least one high-tech fan controller company ridiculing anyone using one of these in a car. The thing is, it's SIMPLE and SIMPLE THINGS FAIL MUCH LESS OFTEN in my experience. Why do I call it simple? Because it's MECHANICAL, not electronic. Many complicated high-tech fan controllers don't have such a good track record, so I wouldn't spout off too much.

Dimensions for this item are about 2 x 1.4 x 1.2 inches (51 x 36 x 30 mm).

The resistor board for this project can be a simple automotive heater fan resistor like this one.

This is Dorman 973-018 made for a 1990-96 Chrysler/Dodge 4-speed fan. It's easily found on-line. Cost is under $10.00. This is designed to use .250 inch (6.3 mm) female crimp terminals, but I found that .312 (7.9 mm) female headlight terminals I had on-hand are a better fit and they have a much better (larger) contact surface. Better contact is good, since I'm using 10 gauge wire here.

This resistor board offers four speeds to choose from.
I am only using three of them (plus a full power relay for full speed).
I measured the resistance values for each circuit on this board and included those below.
There are more test results below.

Dorman 973-018 Pinouts
1. Input: High Speed
2. Input: Medium 2
3. Input: Medium 1
4. Input: Low
5: Output to fan

Resistance Values
0.3 Ohms
0.8 Ohms
1.4 Ohms
3.1 Ohms

I have been told the resistor coils can theoretically get hot when this circuit board is in use.
So maybe it would be best to place this thing where your fingers won't be tempted to touch it.
I mounted mine in the lower left of the fan shroud.
I later began taking IR temp readings from this resistor board when the fan was running and I found it to be not much higher than the shroud or radiator ambient temperature.

To those of you who cried out that this resistor board would MELT, sorry. DIDN'T HAPPEN.

BENCH TESTING FIRST to see if it works.
It was important to me to first see this work and get some good test results for this build before I committed to installing it in my car. I needed it to actually work as expected. So I built a bench-test version with all the components shown so I could get some real performance data.

It's important to keep in mind that this fan controller was tested on my car with the Mark VIII fan fully installed and mounted to my radiator with an intercooler and AC condenser in front of it. I felt that if testing was done on a fan out of the car, the fan would likely pull less amperage with higher RPMs. That would not be very realistic.

TEST #1

BENCH TESTING
This first test was done with the engine OFF, so the battery voltage was not as high as it would be if the engine was running.
Lincoln Mark VIII Fan Speed/Current Testing
(using static 12.7v battery voltage with engine off)
Dorman 973-018 4-speed resistor pinout shown below.

Resistor pinouts from relays shown in above photo.	RPM (Percent)	Amps Peak Spike / Constant Current
Relay 1 Full Power (12.7v static battery)	1800 (100%)	**35.2 / 33.6
Relay 2 High	1400 (77%)	31.9 / 25.0
Relay 3 (Medium 2)	1000 (55%)	14.3 / 13.6
Relay 4 (Medium 1)	650 (36%)	8.5 / 7.4
Relay 5 Low	470 (26%)	4.0 / 3.6
**Peak spike amps were measured when ramping from 77% to 100%. Ramp up from zero to 100% was not recorded, but it's generally known that it can be as high as 100 amps for the momentary initial in-rush of current.

INTERESTING RESULTS:
My first surprise was seeing how the resistor HIGH circuit (through Relay 2) produced a number so much lower than 100%. That 77% figure was not a disappointment at all, since it offered an opportunity for an extra speed choice below 100%. Using fan speed figures like this, you can decide which circuits or resistors you want to use for the fan speeds you like. That low 26% speed might sound ok on paper for a low speed, but once I saw how slow that actually ran the fan, I felt differently. It was too slow for my use. You can see in my diagram up near the top of the page I had originally listed this 26% for my LOW speed. The reality was that it was too low on my car with an intercooler and AC condenser blocking the radiator. So I decided to use the 36% speed as my LOW speed instead.

That 26% low speed might work for a car without an intercooler and AC condenser blocking the radiator. Every car is different.

TEST #2

INSTALLED AND RUNNING
Another test was done after the full installation of the completed controller.
Using running battery voltage (voltage readings below).
Since the 26% low speed was not used, it was not measured here.

I have a 188 degree Fahrenheit coolant thermostat in the engine and the 36% speed seemed to do very well to keep things nice and cool at idle on a warm 85 degree day. If the climate is warmer, then the medium 55% speed may come on occasionally. Keep in mind that every car is different. My car has a very large aftermarket AC condenser (with dual fans) and an intercooler in front of the radiator. Those items obstruct the flow of air to the radiator a lot when compared to car without those items.

Resistor Pinout	Percent	Amps Constant Current @ Voltage
Fan full power	100%	40 @13.3v
High	77%	29 @13.6v
Medium	55%	15.7 @13.9v
Low	36%	8.6 @14v

FINAL SPEED SETTINGS CHOSEN FOR THIS PROJECT

The final speeds I chose have turned out very well.
LOW:	36%
MEDIUM:	55%
HIGH:	77%
FULL POWER:	100%	(only used with override switch)
(The AC activates the 77% speed)

Optional Items

Hella H84988001 Four Relay Sealed Box. Available on-line for about $40 to $50. Pricey, yes! If you're concerned about moisture messing with relays or maybe you just want them to look nicer, this may be a solution. Keep in mind this box is NOT waterproof. There is an o-ring sealed lid, but the bottom is not sealed at all. NOTE: The high-current 80A (full-power) relay will NOT fit in this box, since it uses a couple .375 inch terminals instead of all small .250 inch terminals like standard relays. This box holds only standard relays. The 90 degree mounting ears are removeable and supposedly you can connect two or more of these boxes together side by side.

I found an ABS project box to fit the three Hayden sensors and to help make this installation look nicer. There are a lot of sizes out there for boxes in a couple colors, including black. This box is 4.7 inches long x 2.6 inches wide x 1.4 inches tall O.D. (found on Amazon). I had to do some grinding on the inside to make everything fit inside. A larger box would have been easier, but I wanted it as compact as possible. Cost was about $6.00. The box was painted black before completion.

Since doing this I found a better sized box that I probably would have chosen instead: >>> https://www.polycase.com/lp-55p. Its dimensions are 5 x 3.5 x 1.5 inches (127 x 88.9 x 38.1 mm). It would likely have been a better fit and I think with little or no cutting and carving.

<<< Ford Fan Motor Connector. Fits a variety of Ford/Lincoln/Mercury fans, including the Mark VIII fan I have. A google search will find them in a few places. I have only found them available with 12 gauge wire pigtails. In my opinion that's a bit small for such a fan. I 'm using 8 gauge welding cable.

<<< Dorman Conduct-Tite Terminal, AKA: Ford Standard Block Technician Terminal. This is the type of terminal that goes into the Ford fan motor connector. Dorman offers PN 85367 which fits 14-16 gauge wire and is available on line.

A 10-12 gauge version would be more appropriate, however so far it has NOT been found. If anyone can help with any real sources, please contact me.

<<< So I improvised and successfully used the 14-16 gauge terminals since I couldn't find larger ones. I added one of my large terminal overcrimps to make a solid crimp over the 8 gauge cable I used. Inserting this into the back of the Ford connector housing can be a little tight. I opened up the holes on the back of the connector to accommodate this fat cable. If necessary, a little trimming of the inside of the housing with a hobby knife will help it go in and click. Mine went in and clicked in place without an issue.

<<< PROPER CRIMP tools are important. Try not to use too cheap a crimper or the wrong type for the terminal you're using. Buy yourself something at least as good as this one.
For those of you who are curious about what crimper I use, this is it for 90% of my crimps for non-insulated (and many insulated) open barrel terminals. Thomas & Betts model WT 112M. It runs about $45. I've had this one for 20 plus years.

With some practice, this simple tool can create nice crimps just like a fancy tool.

Check out my video below.
https://youtu.be/Mv92DNdyQXo

<<< For a tool that's a bit more fancy, look for a ratcheting crimper that will do open barrel F type terminals. You can spend a lot of money on one of these tools, but it you hunt carefully, you can find something like this one, which is only $31 for all that stuff. Although sometimes you get what you pay for. The crimp type normally used for open barrel terminals I offer in my page is the die set in the center. The others might come in handy, so they would be a bonus. I don't own this one. My fancy racheting crimper was about $80 ten plus years ago from Summit Racing. This one is cheap and might be worth the cost, or it might explode. You can never really tell until it's in your hands.
HERE: https://www.amazon.com/dp/B01CVH8JNO?psc=1

Here's a good crimping guide for beginners:
http://www.xj4ever.com/crimping my style.pdf

<<< This is an aluminum Chassis Mount Resistor. It is NOT something I have tested or used in this project. The reason this info is here is because It has been suggested for durability, particularly in corrosive or wetter environments. Some of you might want to consider a different style resistor instead of the Dorman resistor board I used. Most of the suggestions people have sent have been pointing to ceramic automotive resistors, such as those used for ignition, AC and cooling fans older cars. The problem I encountered is that there are very few choices for varied resistance values in ceramic, so it may take a lot of trial and error to get that working well.

So I began looking closer at these Chassis Mount Resistors. The dimensions for the models listed below are 65 x 47 x 26 mm (about 2.5 x 1.9 x 1.25 inches). They run about $10 each and they're rated for WET CONDITIONS. Most ceramic resistors have only a 30-40 watt capacity. The chassis mount types I have listed below all have a 100 watt capacity. You would need three of them to come close to duplicating the three speeds I have achieved with the Dorman resistor board, however I have not tested any of these yet to see what speeds they will actually generate. Since the four ohm values I found in the Dorman resistor board were 0.3, 0.8, 1.4 and 3.1 (I'm not using 3.1 ohms), you can try some that are reasonably close to that, such as 0.22, 1, 1.5 and 3 ohms.

A source I found for these is DigiKey Electronics: http://www.digikey.com/product-search/en?keywords=resistor.

PN A102367-ND 0.1 ohm
PN A102368-ND 0.22 ohm
PN A102369-ND 0.47 ohm
PN A102106-ND 1 ohm
PN A102185-ND 1.5 ohms
PN A102360-ND 2.2 ohms
PN A103830-ND 3 ohms

If you incorporate something like this in your build, please email me. I would like to know how your project goes. CONTACT ME.

Completed Project Review

After TWO years of use, this controller has worked perfectly. Zero glitches or worries. That's nice for a change.

<<< Here's the full setup installed in my 240. As you can see I opted for the fancy Hella relay box. Those four relays in the box are for AC, Low, Medium and High speed.

<<< Another angle. That relay on the left side of the Hella box is the 80A full power relay. It's triggered by the override switch on my dash. Hopefully it won't be needed, but it comforts me to have it just in case.

This setup has been used in 105 degree plus Texas climate it works exceptionally well.
The 77% speed I chose for the AC works very well also.

<<< Here's another view of the Dorman resistor board mounted in the lower left corner of the fan shroud.
That is 10 gauge high-flex wire. The terminals are .312 inch (headlight terminals), since I found they actually fit better and provide more contact area than the .250 inch terminals that are normally used on there.

There are people who thought this resistor board would melt. Two years later and all is working perfectly. So there, stupid doubters.

BAD RECOMMENDATIONS
<<< This is worth mentioning if you decide to used a Hayden 3653 temp sensor. It concerns mounting the radiator fin probes in or on the radiator. This image is from their instructions. They supply the shown probe mounting parts and tell you to mount the probe in a supplied metal/rubber mounting strap that is then isolated from the radiator by a foam pad. THIS IS A REALLY BAD IDEA. What this does is delay radiator temps from quickly transmitting to the probe. The delay with mounting it this way is substantial. It has slightly less of an effect when hot air from the radiator is blowing through and past the probe, but there will be signiificant delay when warming up the engine (if the fan is not blowing) or if the car is not moving and air is not flowing yet. The delay will be such that the radiator will heat up PAST the setting you want for the fan to come on, so then your fan comes on late. Then it will DELAY the fan from shutting down as the radiator temps drop off, causing wide swings of the fan on/off cycle. You'll curse Hayden because you wont be able to accurately dial in your settings.
It's just bad. Don't follow those instructions.

<<< DO THIS INSTEAD: The probes that come with these units are a bit fat and would not slip into my radiator fins without a lot of force. This may be why Hayden wrote those instructions that way. I didn't want to risk damage to my expensive aluminum radiator by bending things and forcing the probes in, so I mounted the probes tightly against the radiator fins as shown in this photo using thin zip-ties. While it might be hard to tell in this photo, the full length of each probe is very snug against the radiator fins and they have good, solid contact. Sensor activation with this method is quick and accurate. Faith in Hayden has been restored.

<<< Here's the override switch I placed on my dash. The small LED bulb below the switch illuminates green when the fan is on.

<<< The LED turned out to be too bright with full 12 volts, so I added a 220k ohm resistor to the power wire. Now it seems just right with a low green glow.

The final speeds I chose have turned out very well.
LOW:	36%
MEDIUM:	55%
HIGH:	77%
FULL POWER:	100%	(only used with override switch)
(AC activates the 77% speed.

Your comments are welcome. CONTACT ME

PARTS INVENTORY

Update 2017: The dorman version of the Lincoln Mark VIII fan with shroud is available on Amazon here cheap: https://www.amazon.com/gp/product/B001SGHK1W/ref=pe_850140_225176060

(These are the parts I can remember. Some items are available in my Relay Page or Harness Parts Page if needed).

Relay - Picker High Current 80A relay (SPDT). Qty 1. Available here: https://www.prancingmoose.com/volvorelays.html#highcurrentrelay

Relay - Tyco gray “101” 40A relay (SPDT). Qty: 4. Available here: https://www.prancingmoose.com/volvorelays.html#1259926-101gray

Relay plug socket, interlocking, 5-pole. Qty: 4. Available here: https://www.prancingmoose.com/volvorelays.html#relayplug

Optional - Hella H84988001 Sealed Box for four relays. Qty: 1

Relay high-current plug socket, 5-pole. Qty: 1. Available here: https://www.prancingmoose.com/volvorelays.html#highcurrentplug

Fuse holder (mini fuse) with 5A fuse (18 gauge wire). Qty: 1

Fuse holder (maxi fuse) with 50A fuse (8 gauge wire). Qty: 1.

Hayden 3653 adjustable temp sensor. Qty: 3.

Resistor pack - Dorman 973-018 4-speed fan resistor. Qty: 1.

Diode - PN IN5408. Qty: 1.

Wire - 8 gauge (high flex welding cable recommended). Qty: about 8 feet red.

Wire - 10 gauge (high flex marine grade recommended). Qty: about 2 feet red.

Wire - 16-18 gauge auto primary wire. Red and black. Qty: about 8 feet red and black.

Heat-Shrink Tubing - Varies sizes (maybe 3/8 to 1/2 inch) in black or red and black.

Toggle Switch - On/Off for high speed relay override wire. Dash mounted. Qty: 1.

Crimp terminal - .375" (9.5 mm) female, 6-10 gauge (for high-current relay). Qty: 3. Available here: https://www.prancingmoose.com/blackvinyl.html#.375inchterminals

Crimp terminal - .312" (7.9 mm) female straight, 10 gauge (for Dorman resistor). Qty: 4. Available here: https://www.prancingmoose.com/blackvinyl.html#headlightplugs

Terminal Overcrimp (optional) - Large (for Dorman resistor terminals using 10 gauge wire). Qty: 4. Available here: https://www.prancingmoose.com/blackvinyl.html#overcrimps

Crimp terminal - .250” (6.3 mm) female, 10-12 gauge (for relays). Qty: 7. Available here: https://www.prancingmoose.com/blackvinyl.html#.250inchplugs

Crimp terminal - .250” (6.3 mm) female, 14-18 gauge (for relays). Qty: 12. Available here: https://www.prancingmoose.com/blackvinyl.html#.250inchplugs

Terminal Overcrimp - Large (used for Ford terminals in the fan motor connector). Qty: 2. Available here: https://www.prancingmoose.com/blackvinyl.html#overcrimps