1988 Mondial 3.2 Odometer adding miles

The diodes can be tested in stiu. The transistors must be removed to test. All can be tested with a cheap DVOM. Google testing diodes, testing transistor. https://vetco.net/blog/test-a-transistor-with-a-multimeter/2017-05-04-12-25-37-07

But since you have to remove the transistors to test, I'd just replace them.

 

Datasheet for Electrolube SPG35SL

It's sounds very sticky, but the datasheet says:

 

I have been successfully using SPG (not the sticky A version) - it's very finely applicable through a super-fine nozzle:
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It has an expiration date ? So we have to open that meter every year ?

 

I do have a tube of Tamiya Grease (ref 87022), it's a clean (read milky translucent grease) can be ordered online, and cheap. They also sell a switch lubricant grease that does wonder in the toggle and mirror switches. These hobby grade products are perfect if you need a small quantity.

 

Got the instruments off without too much trouble. Everything appears to be in order with nothing obviously wrong or out of place.

The odometer motor is getting power through the small red and blue wires. With the connector removed, no more counting up.

Not sure what to check next or how to diagnose further…
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I tried to take a reading on the back of the red and blue connector and got something like 3.8V on it with the key on.

 

What does the back of the circuit board look like? Any signs of cracked tracks, dry joints, etc? Can you see the first component that the red/black wire goes to (pin 5 on the main plug). That's the speed sensor signal coming in.

I didn't think there would be so many wires on the odometer itself (unless some are internal lighting). Can you take the white plastic cover off and see where the wires go?

 

I’ll have to pull it out again to have a look - the back of the board seemed fine.

In the meantime, I now have to figure out why I’m not getting heat in the car. Thinking the thermostat could be at fault. Ferrari ownership is quite hands on!

 

Why the thermostat? You mean your heater isn't working?

 

When I start the car up, it will provide some heat initially but then fades to cool air. It’s also operating quite below temperature with the water temperature showing maybe a 150-180F range, but mostly on the lower end and especially if travelling at any speed.

 

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Same on my car, generally around 180. But the heater works perfectly with 180deg water... I think your heater valve may not be operating properly.
Disconnect it and see if you get 12V or 0V at the plug dependent on your heater knob position.

 

It’s much lower in my case, which has me concerned about the engine temp.

Where is the heater valve?

 

passenger side below the dash, the hose coming up through the sill entering the core and exits and is regulated by the valve:
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Thanks! That’s very helpful. Guessing that I’ll need to somehow catch the coolant in the hose to get the valve off.

 

Just unplug it and test the signal first to rule out any issues in the HVAC system. It's an ON/OFF signal from the ecu, so you either have 0V (heater ON) or 12V (heater OFF). Only if that's ok I'd remove the valve and yes in that case you need to catch a bit of water (between the exit of the core and the valve).