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My dash lights were not working and my tachometer is very intermittent. So I pulled the dash cover and started digging in.
on the back of the tachometer there's a 7 pin ribbon connector.
PIN 1 : switched power
PIN 2 : trigger (+ from the ECU)
PIN 3 : left turn signal
PIN 4 : TCS lamp
PIN 5 : harness blank (not on US models. lights on indicator)
PIN 6 : ground
PIN 7 : lighting PIN 7 goes to PIN 5 OF RHEOSTAT.
tachometer:
Put multimeter in continuity beep mode. Put the + lead in the back of Pin 1, Put
the - lead in the back of pin 2. You should hear a buzz instead of a beep. Rev
the engine and the buzz will go up in pitch. If you got this far, your rev
signal triggered by the ECU is working - because you're getting continuity between +12 and the trigger. Anyway... I am getting signal at least that far. This eliminates the ECU and wiring up to the tachometer circuit board.
I removed the tachometer from the entire unit just to make it easy to plug into the harness and do electrical checks. With the connector plugged in to the ribbon, I was able to confirm I had continuity from each pin in the harness to the screws that connect into the tachometer circuit board (the one in the tach not the blue one). I don't think I have an issue with my circuit board or wiring. I think the tachometer is faulty.
Into the shop with my magnifier and my DVM and inspected it as well as I could. The capacitor did not seem to be in bad condition. I confirmed continuity across all the areas of the board that I thought made sense. I didn't see any areas shorted out, and didn't find any with my electrical checks. Yet my tach does not work.
Is there a way to test the tachometer on the bench? Can I apply straight 12v to pin 2 and see the RPMs shoot to the moon? Can I send it a square wave of +5v from an arduino to get it to start moving up? I don't know at all.
Anyway, I am ordering a new tach unit and that should resolve the problems. Looking for ideas on resurrecting this tach though. The internet lacks details on the board itself.
no dash lights:
Pin 7 of the tach connected is controlled by Pin 5 of the Rheostat. Both are
labelled. If you have power at pin 5 you should have power at pin 7 of the
harness. If not something is messed up in the harness. In this case. I did not have power at pin 5 from the rheostat. My rheostat is faulty. I have instead added a jumper pin 5 of the rheostat (brown/white) to the green wire switched power (pin 1? i forget). Now I have full brightness at my dash but my dimmer does not work. That's a compromise. But rheostats in good shape are harder to find. A simple rheostat like the 900 has could be installed for the dash lights if desired. Pulling apart the rheostat could also reveal bad solder joints etc.
posted by 131.106.22...
1
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