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VOLVO 240 Instrument Cluster
and Gauge Electrical Stuff


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240 Instrument Cluster Wiring
240 Temperature Compensation Board
240 Electronic Speedo Re-Calibration 52 mm Dead Clock Repair
Adding a LARGE TACH to your 240
Adding a SMALL TACH to your 240
Improving 240 Gauge Lighting (plus LEDs)
Ambient Temperature Gauge


VOLVO 240 Instrument Cluster and Gauge Wiring
Below I have compiled 240 instrument cluster wiring for several different years. 

If you're converting an instrument cluster to fit a different year than intended, pay strict attention to any pins that have changed.  A lot of them did change.  Some even changed from power to ground.  If you plug in the wrong wire, you can quickly damage a circuit board.

If you can help improve this info, please feel free to email.


Early 240 R Sport Gauges
<<< Here's a diagram (PAGE 1) showing the pin-outs for the 240 R-Sport instrument cluster. This cluster uses a cable type speedometer.

Some of the pins in these images are noted with "Pos" or "Neg."  These notations refer to the circuit polarity going to the lamps related to those circuits. 

For example, Pin 31/2 supplies a signal to the Brake Failure Lamp.  That signal is a GROUND (Neg), which completes the circuit for that bulb, since it already has a power circuit supplied by the circuit board, which originates through Pin 32/2. 

Another example: Pin 31/12 supplies a signal to the OD Lamp. This signal is POSITIVE (12v), which completes the circuit for that bulb, since it already has a GROUND supplied by the circuit board, supplied through Pin 32/A.
<<< Here's PAGE 2 of the R-Sport cluster diagram.



1977-78 240 Gauge Assembly
<<< Here's a diagram showing the pin-outs for the 1977-78 240 instrument cluster. This cluster uses a cable type speedometer.

Some of the pins in these images are noted with "Pos" or "Neg."  These notations refer to the circuit polarity going to the lamps related to those circuits. 

For example, Pin 31/2 supplies a signal to the Brake Failure Lamp.  That signal is a GROUND (Neg), which completes the circuit for that bulb, since it already has a power circuit supplied by the circuit board, which originates through Pin 32/2.

Another example: Pin 31/12 supplies a signal to the OD Lamp. This signal is POSITIVE (12v), which completes the circuit for that bulb, since it already has a GROUND supplied by the circuit board, supplied through Pin 32/A.



1980 240 Gauge Assembly
<<< Here's a diagram showing the pin-outs for the 1980 240 instrument cluster. This cluster uses a cable type speedometer.

Some of the pins in these images are noted with "Pos" or "Neg."  These notations refer to the circuit polarity going to the lamps related to those circuits. 

For example, Pin 31/2 supplies a signal to the Brake Failure Lamp.  That signal is a GROUND (Neg), which completes the circuit for that bulb, since it already has a power circuit supplied by the circuit board, which originates through Pin 32/2.

Another example: Pin 31/12 supplies a signal to the OD Lamp. This signal is POSITIVE (12v), which completes the circuit for that bulb, since it already has a GROUND supplied by the circuit board, supplied through Pin 32/A.



1984 240 Gauge Assembly
<<< Here's a diagram showing the pin-outs for the 1984 240 instrument cluster. This cluster uses a cable type speedometer.

Some of the pins in these images are noted with "Pos" or "Neg."  These notations refer to the circuit polarity going to the lamps related to those circuits. 

For example, Pin 31/1 supplies a signal to the Brake Failure Lamp.  That signal is a GROUND (Neg), which completes the circuit for that bulb, since it already has a power circuit supplied by the circuit board, which originates through Pin 32/A.

Another example: Pin 31/4 supplies a signal to the OD Lamp (for M46). This signal is POSITIVE (12v), which completes the circuit for that bulb, since it already has a GROUND supplied by the circuit board, supplied through Pin 32/4.
 
Automatic Transmissions: An automatic transmission car will not have a terminal in Pin 31/4 (M46 overdrive lamp). So if you're converting a car from auto transmission to an M46 manual, you'll need to add a 2 mm female terminal to the round plug at 31/4. Also you should remove the terminal from Pin 34, which powers the "OD OFF" lamp used for the automatic transmission OD light.







1987 240 Gauge Assembly
<<< Here's a diagram showing the pin-outs for the 1987 240 instrument cluster. This cluster uses an electronic speedometer.

Some of the pins in these images are noted with "Pos" or "Neg."  These notations refer to the circuit polarity going to the lamps related to those circuits. 

For example, Pin 31/1 supplies a signal to the Brake Failure Lamp.  That signal is a GROUND (Neg), which completes the circuit for that bulb, since it already has a power circuit supplied by the circuit board, which originates through Pin 32/A.

Another example: Pin 31/4 supplies a signal to the OD Lamp (for M46). This signal is POSITIVE (12v), which completes the circuit for that bulb, since it already has a GROUND supplied by the circuit board, supplied through Pin 32/4.

Automatic Transmissions: An automatic transmission car will not have a terminal in Pin 31/4 (M46 overdrive lamp). So if you're converting a car from auto transmission to an M46 manual, you'll need to add a 2 mm female terminal in the round plug at 31/4. Also remove the terminal from Pin 34, which powers the "OD OFF" lamp used for the automatic transmission OD light.



1993 240 Gauge Assembly
<<< Here's a diagram showing the pin-outs for the 1993 240 instrument cluster. This cluster uses an electronic speedometer.

Some of the pins in these images are noted with "Pos" or "Neg."  These notations refer to the circuit polarity going to the lamps related to those circuits. 

For example, Pin 31/1 supplies a signal to the Brake Fluid Level Lamp.  That signal is a GROUND (Neg), which completes the circuit for that bulb, since it already has a power circuit supplied by the circuit board, which originates through Pin 32/A.

Another example: Pin 34 supplies a signal to the OD Lamp. This signal is POSITIVE (12v), which completes the circuit for that bulb, since it already has a GROUND supplied by the circuit board, supplied through Pin 32/4. 

NOTE regarding using an M46: This later cluster does not have a separate lamp for an M46 OD lamp, since that lamp position was replaced by an SRS lamp.  So you may use the OD arrow lamp if this cluster is used with an M46 transmission.  Otherwise some custom work would need to be done to add a traditional OD lamp.  Here is some info submitted by a customer who modified his late 240 cluster: 
https://www.240turbo.com/WhiteFaceGaugesStyle5.html#clustermod



Dealing with the
Temperature Compensation Board
 in your 1986-93 240
I won't go into great detail here, since there is already an excellent article on this subject linked below.  In a nutshell, Volvo got tired of people complaining about fluctuating needles on coolant temperature gauges.  Fluxuating coolant temperatures is normal, however when the gauge fluxuates, many customers get freaked out by it. The coolant thermostat is supposed to even things out.  But Volvos in the 1980s were designed for cooler northern European climates and there are many U.S. regions that will easily max out an old 240 cooling system.

To make customers happy, for the 1986 year model Volvo began installing a special circuit board in the instrument cluster that changed the function of the coolant temperature gauge so that it would remain stable in the middle or "normal" range at all times unless the engine was very cold or very hot.  The gauge then had only a few set readings instead of a true variable reading.  Customers were happier.

These temperature compensation boards generally worked fine until they got old and began failing. A failing board would cause mysterious high or low fluctuations for no reason. If you're trying to determine what your high or low temperature fluctuations REALLY mean, you can buy an infrared (IR) temperature reader and check your top radiator hose temps for abnormal changes. If you find that temperatures are actually pretty stable, then your temperature compensation board may be failing.

Here's a video showing this board being removed: https://www.youtube.com/watch?v=xpyFEWoqiaE

<<< At this writing these boards can still be found new, however they're expensive.  iPd has them here: https://www.ipdusa.com/products/5671/107045-instrumentation-voltage-stabilizer-compensator-board

To fix the problem, iPd began offering a simple bypass wire you could buy for cheap: https://www.ipdusa.com/products/5670/108262-temperature-board-bypass-kit.  They also offered replacement compensation boards for more money.

You can also read the following instructions for your own DIY repair . . .ARTICLE HERE:  https://cleanflametrap.com/tempFaker.html

And if your interested in more DIY repair, Peter A. submitted the following: 
"The circuit is kind of clever. It can be repaired rather than just eliminating it.  It does require a soldering iron and a solder sucker to desolder the old parts. 
Pretty much the only things that will fail is the integrated circuit U1 or output transistor Q1, both of which can be purchased on-line from Digikey or similar places for about a dollar. U1 was bad on my board.  After 25 plus years it would also be wise to replace the electrolytic capacitor C1."
Click here for a PDF diagram and photo of these circuits:  https://www.davebarton.com/pdf/TempBoardCircuits.pdf (270kb)

And Dirk W. submitted the following for those interested:
"Lots of people will claim you need a new temperature compensation board (PCB), but that's not what's really wrong most of the time.  I have found that the metal pins that are mounted to the main cluster PCB are generally not properly soldered to the PCB.  They APPEAR to be soldered, but if you touch a soldering iron to the solder blobs that cover the heads of the pins, you will find that the solder is not wetted to the pin heads and these connections are almost always bad somewhere.  A little work with some sandpaper on the heads of the pins and resoldering the heads of the pins to the PCB will fix most temperature gauge issues."



240 Electric Speedometer Custom Re-Calibration
(Applies to 1986 and later 240 models. 700/900 models too)
This information has been compiled from discussion threads in Turbobricks, the Brickboard and from customer contibutions.  It's a simple mod, but some clarification was needed to make it simple for the rest of us. Using modern electronics, you may add a variable trimpot (rheostat) to alter or adjust the signal the speedometer receives from the speed sensor in the rear axle.

First thing you'll need to do is disassemble your instrument cluster and remove your speedometer.  If you don't know how, instructions for that can be found in my 240 Odometer Repair Page

<<< Depending on the year of your 240, you'll see a resistor like one of these two photos. That is the calibration resistor. It is static (or non-adjustable).  It was installed by Volvo to alter the speed signal for the specific speedometer they selected for your car.  The original resistor has been measured by others at around 51 to 56 ohms.  By changing the value of that resistor, you can change the signal received by the speedometer.  Some have installed different static resistors to reset their calibration. A few have installed variable resistors so the calibration can be fine tuned when driving.  That's what this article is about. 

1. Using a soldering iron, heat the solder behind the original resistor and remove it.  Simple task.

<<< 2. Next insert a stripped wire into each hole and solder them on the back so they're secure. You may use 18 to 22 gauge wire or smaller.  If the holes need to be opened up a little, use a small drill, then solder.
   
<<< 3. Here is an example of a 100 ohm variable resistor (adjustable between zero and 100 ohms). A "linear" type is preferred.  These can be found on eBay and are very cheap (usually made in China). Often they're offered in lots of 5 or 10 for under $10.  Feel free to put an ohm meter on it and find the two pins needed for the wire hookups.  Polarity is not important.  While you're at it, set it somewhere in the middle (50-55 ohms).

<<< A customer sent this pic.  He mounted the variable resistor behind the hole formerly occupied by the clock adjuster.  This way he could tune it easily after the dash was assembled and it looks very clean.  There's no need to get this fancy if you don't want to. The resistor can also be put under the dash or anywhere within reach depending on wire length. 

If you can offer any new information or better ideas for this mod, please email.

Resources for more info: https://www.brickboard.com/RWD/volvo/853622,   https://forums.turbobricks.com/showthread.php?t=239021,   https://forums.turbobricks.com/showthread.php?t=258248



Adding a Large Tachometer to your 240
<<< This is the very first modification I did to a 240 back in 1990.  It's a very basic install, but can be a bit puzzling for a beginner. These instructions will also show you how the small clock is installed. 



Adding a SMALL Tachometer to your 240
While less popular than adding a large tachometer to your gauge cluster, Volvo made a small 52 mm tachometer available for 240 owners. 
They are fairly rare to find these days, but they can still be found used.  Here are diagrams for wiring it up.  

CLICK HERE FOR INSTRUCTIONS (pdf)



Adding an Ambient Temperature Gauge
This should help if you're installing one of these.




Repairing a Dead 52 mm VDO Clock
If you have a dead small clock like this, you can repair it. 
There are two small capacitors inside that usually fail after many years, making the clock useless.  They're cheap to buy and fixing is easy. 


Needs:
  Soldering iron and some low-level amateur soldering skills.

Read this tutorial: https://forums.pelicanparts.com/porsche-911-technical-forum/913721-vdo-clock-repair-incl-pictures.html

More needs: Pick up some 100uF (micro Farad) 16v Electrolytic Capacitors. You'll need TWO for each clock.
These typically come in large quantities and are cheap: https://www.amazon.com/100uF-5X11-Aluminum-Electrolytic-Capacitors/dp/B074QGYVY3/

Since polarity is important, become familiar with how to find polarity on a capacitor:
https://startingelectronics.org/beginners/components/capacitor/

If you have a 1979 or older 240, here's some info specific to your clock:
https://forums.turbobricks.com/showthread.php?t=280520&highlight=clock

Short video on repairing a VDO clock:
https://www.youtube.com/watch?v=4e0qJ-i9l_g

The clock hands may be removed by simply pulling them off or gently pry with a screwdriver. 





Improving the Lighting in Clocks and other 240 Gauges
I've done a few experiments over the years to improve gauge lighting in my 240.  I'll share some of that here.

 
DIMMER BYPASS
I did this simple mod years ago and have been happy with it ever since.  If you have dim dash lights in your 240, even when the dimmer switch is set to full brightness, you should know the 240 dimmer switch will not provide full power to the bulbs, even at the full brightness setting. If you want to verify this, hook up an Ohm meter and check the resistance and you'll find the dimmer supplies significantly less current at full brightness than if the lights were simply wired to battery power.. 

You can bypass the dimmer and then your dash lights will either be off or full bright.  All you need to do is bridge the two connections on the back of the dimmer (see pic below).  This can be done by making a short cable with two male .250 inch (6.3 mm) spade terminals. 

If you're not sure about this, try it temporarily are see how you like it. You'll find that after bypassing the dimmer, all of the dash and gauge lights will be brighter.  
Then you'll just need to decide if having that dimmer switch in place is worth having dimmer dash lights.

Access to the back of the dimmer can be done by removing the instrument cluster and then you can reach in and do your work.  


LED CLOCK BULB
You can replace the bulb in your clock with an LED bulb. The bulb is found in this black plastic bulb holder on the back side. In this instance there is only one wire going to the bulb. That's the power wire. The bulb is grounded through the clock metal case.  So when you're testing a bulb in a clock like this, be sure to ground the case (the ground wire is the black wire seen below that's connected to a tab on the case).

<<< Here's the standard bulb found in the above clock.  It's known as a WEDGE base bulb. This particular size may be know as a T5, 74, Osram 2721, W2x4.6d and others. It typically uses about 1.2 watts.  This bulb is also found in a number of other places in your 240 dash and in other gauges.

The bulb simply pulls out of the black bulb holder. If it's stuck, it's from years of corrosion and it just needs more force to pull it out.  If this happens, you might wear gloves, because you might break the bulb and cut yourself.
Here's a comparison test I tried below using the below LED bulb I picked up on line.  The photo with the brighter LED bulb is pretty easy to spot below. 
Keep in mind that LED bulbs are usually polarity specific, so if you plug one in like this one and it doesn't work, try pulling it out, turning it 180 degrees and plugging in again.


Your results may vary.  Some cheap Chinese LED bulbs have crappy quality and it's hard to know what's good and what's not until you try it. Sometimes you can read Amazon reviews if you think they're trustworthy. I've tried LED bulbs for a few various places in 240s and some worked well and some have died quickly.
The LED bulb used above is found here: https://www.amazon.com/gp/product/B0798R76CR/


 


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