I've been working on the instrument cluster in my '90 240 to get the speedometer working, turns out the chip might be toast. Someone before me had attached the odometer wire to a golden prong.

The recently installed tachometer works along with the fuel guage, but little else.

Before this the lights and blinker indicators were fine, but not the indicators dont work, and the only lights that flash when you put the key in 2 are "SRS" and "Check Engine".

My fuses are fine, and they're good quality brass types, all the same.

Did I break something? Which plug controls the lights and such?

EDIT: I just fixed the light issue, forgot to put a plug in, now everything works beyond the speed-odometer.

 

1992 240 instrument cluster, per greenbook wiring diagrams:

speedo: 3 pin right angle connector 233:
233/1 - black - ground
233/2 - green/white - speed signal from sender in rear axle
233/3 - blue - switched power from ignition switch 15R

full circle connector 31:
31/1: grey - brake fluid level indicator
31/2: yellow - temp gauge sensor
31/3: white-red - high beam indicator
31/4: brown-black - SRS (airbag) fault
31/5: black - oil pressure light
31/6: blue-black or yellow(?) - speed output to ECU and cruise control
31/7: blue - left turn indicator
31/8: blue-green - right turn indicator
31/9: white - unswitched power from fuse 8 for clock
31/10: brown - rheostat for dimming dash lights
31/11: red - alternator/battery light
31/12: - blue-yellow - bulb failure warning sensor

half circle connector 32:
32/1: grey - fuel level sensor
32/2: brown - parking brake
32/3: green - ABS fault
32/4: black - main ground
32/A: grey - fog lamps

back of clock/tach:
31 - black - ground for external small clock
30 - red? - unswitched power for external small clock
58 - green - dashboard dimmable light power for small clock

single pin 1 bottom back of tach - red-white from ignition coil pin 1

single blade connector 34 (near lower corner by fuel gauge)
- yellow-red - overdrive disabled or upshift light.

single blade connector 235 (near lower corner by tach/clock)
- yellow - for diesel glowplug,
OR - pink-white - check engine for OBD

 

It was that odd connector 31 I forgot to plug in, thank you for that Greenbook info though, thats information I've been hunting around for.

Weirdly the odometer gears are fine, I've adjusted the speedometer wires so they grip real nice.

 

You say the odometer gears are fine - does the odometer work? If both the odometer and speedometer don't work (and everything else in the cluster does), then you may have fried the chip in the speedo board. You can replace it if you are handy at soldering. I think new chips can be ordered from china. I actually replaced mine with a chip from a junkyard speedo.

 

The gears are fine but neither the odo nor speedo work, everything else works though.

When the cars been driven for a long time the speedometer will eventually work but not the odometer.

 

Check the solder joints for the motor that drives the odometer. THey may be cracked and have an intermittent connection. I would use a solder sucker to remove the old solder and re-solder with new. Many times there are tiny cracks that aren't readily visible unless you have a magnifying lamp - or better yet one of those fancy soldering microscopes.

 

I'll inspect that motor a bit closer, may very well be weak solders.

I have considered swapping speedometers but that might tack on an extra 100,000 miles, unless I swap the odometer part or something.

 

where do you order the chip from China from please? I may have fried mine.

 

Don't know where to buy the chip but it is an ITT UAF2115 chip. Google it and you might find some for sale.

 

31/10: brown - rheostat for dimming dash lights. I should be getting how many volts.? I am getting about 5. Grounds are good as are bulbs and connections

 

the rheostat voltage would vary with the dimmer settting. nearly 12V for brightest, nearly 0V for dimmest, values in between for anything else.

 

In my brilliance I fed voltage directly to the clock and then smelled something burning.
I have an 89 guage cluster that has all the warning lights go on. Now my 87 cluster has no warning lights going on. Did I fry the ITT UAF2115 chip?

 

the 2115 is strictly part of the speedometer, nothing else, it converts pulses from the rear axle sensor to volts to drive the speedometer movement.

the lights on a 240 are all directly wired to various things. some warning lights are lit by the input signal being grounded, others by the input signal going to 12V, you'd have to look at a wiring diagram to see how it all works, and my diagrams aren't 'shareable' (they are heavily copy protected)

 

Smoked a connection on the printed circuit board. Have a friend who does electronic soldering better than I .
Are 1989 cuircit boards interchangeable, with 1987 and can I swap speedos as well,87 to 89 board. temp and fuel seem to swap.

 

fried the copper tap. bypassed it on the back.