| VOLVO 240 Instrument Cluster and Gauge Electrical Stuff |
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Updated: August 4,
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| 240 Instrument Cluster Wiring |
240 Temperature Compensation Board |
| 240 Electronic Speedo Re-Calibration | 52 mm Clock Repair |
| Adding a Large Tach to your 240 |
Adding a Small Tach to your 240 |
| 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. By not paying attention or by just plugging it in and trying it out, you can quickly destroy a circuit board. If you can help improve this info, please feel free to email. |
 <<< 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 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. |
 <<< 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 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 a diagram showing the pin-outs for the 1980 240 instrument cluster. This cluster uses a cable type speedometer.Some of the pins 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 a diagram showing the pin-outs for the 1984 240 instrument cluster. This cluster uses a cable type speedometer.Some of the pins 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. An automatic transmission car will not have a terminal in Pin 31/4 (M46 overdrive lamp). So if you're converting at car from auto transmission to an M46 manual, you'll need to add a 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. |
 <<< Here's a diagram showing the pin-outs for the 1987 240 instrument cluster. This cluster uses an electronic speedometer.Some of the pins 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. An automatic transmission car will not have a terminal in Pin 31/4 (M46 overdrive lamp). So if you're converting at car from auto transmission to an M46 manual, you'll need to add a 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. |
 <<< Here's a diagram showing the pin-outs for the 1993 240 instrument cluster. This cluster uses an electronic speedometer.Some of the pins 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: 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. |
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| 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
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 <<< 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-boardTo fix the problem, iPd began offering a simple bypass wire you could buy for cheap: http://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: http://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." |
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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, http://forums.turbobricks.com/showthread.php?t=239021, http://forums.turbobricks.com/showthread.php?t=258248 |
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| 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. |
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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) |
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Repairing a 52 mm VDO Clock
If you have a dead small clock like this, you can probably 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: http://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: http://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 |
