Help with 93 240 instrument cluster - speed/temperature
 

Send cluster off for repair. I have a 92 244 gl and the cluster works perfectly except zero temperature reading. Everything else works.

When I put that cluster into a '93 245, the fuel reads zero, the temp reads zero and the speedo will move up to 20mph, then bounce a bit. Speeds of 60mpg gives a reading of zero. Speeds over 20 give varying unstead readings...nothing over 40 at any time.

The lights all work on the cluster. THE ABS is on all the time as is a burned bulb indicator.

When I got the car, a red/white line was attached directly to the temp guage. Puzzling. I sent if off for repair and it looks like all is ok except the temp guage.

ANY idea of where to look for the source of the erratic speedo? I can read about 800 ohms on that sensor at the speedo plug.

ANY idea of what is wrong with the temp circuit on the cluster? I suspect a resistor is between the input from the sensor and the guage, but I have no idea. Something is missing since it is dead on my other car.

Any ideas of what to look for? I surely hope the wiring hasn't been butchered by someone.

the engine coolant temp sensor is screwed into the intake manifold side of the engine, under the intake manifold, its the sensor with one yellow wire. the temp sensor is a variable resistor, lower resistance at higher coolant temps.

I'm trying to remember what that red-white wire in the back of the cluster is, I think it might be for a cluster that has a tach instead of a clock, or something like that.

the speedo sensor is in the differential and sends pulses. different cars have different tone rings, ABS is different than non-ABS, and I think it varies from some years to others, but I don't know which are what. the speedo has to be matched to the tone ring and wheel size 240 wagons have different speedos than 240 sedans, too, as they run a slightly larger tire size

That's all correct as far as I can tell. The 245s speedo seemed to work fine in the 244..not sure as to exact accuracy, but it appeared correct to me.

I found that the red/white connection which was attached when I got the car should NOT have been attached and have not put it back into play since I got the repaired speedo back....it is attached to the tach which this cluster does not have.

I have swapped speedo sensors with no difference in behavior. I suspect I have a wiring issue out side the cluster that I have not yet found. But for both gas sensor and speedo misbehavior to be wrong is a problem. It further appeared that someone installed a junk yard replacement speedo since it was marked that way when I removed it. Apparently whoever did the work thought he knew what he was doing in plugging in the red/white wire, so I'm afraid he may have gone where angels fear to tread.

Plugging the red/white wire into the blank spade next to the yellow wire ususally means death to the 2115 chip on the speedometer circuit board.

When swapping instrument clusters, it is important to make sure that you get a cluster for your particular model. Cars equipped with ABS have a different cluster than cars without ABS.

the speedo error between 185/70-14 (sedan) and 195/70-14 (wagon) is pretty minimal. probably about the same as the error I have after switching from 195/60-15 to 205/55-16 :)