Hello there. My rev counter on my mk2 is intermittent. My old tachfix signal adaptor fitted ten years ago seemed to have corroded on a resistor inside and subsequently failed whilst the car was stored off the road for a number of years. I recently fitted a new danpy version, all connections are soldered and heat shrunk. The rev counter started to work again when I tried the car once this was fitted. I started to use the car a bit again, and upon driving it about I noticed the rev counter soon packed up again. It seems to work intermittently, one minute it’s fine, the next nothing. A couple weeks back the car seemed to be a bit harder to start from cold, and it didn’t want to idle. When it finally did start and run, the revs were higher than usual on choke. The rev counter was working and showed it idling at 11-1200rpm. I thought maybe crank sensor could be to blame, so recently replaced that original one with a new Bosch version. On startup all seemed good, car runs spot on again and rev counter working, but then rev counter stopped showing anything after a couple of minutes of running. The adaptor is new, the cps is new, and the wiring is mechanically/electrically sound, no bad connections known anywhere. Anyone have any ideas? Cheers
I understand the engine is running decently but the tacho isn't working correctly? There is a potentiometer on the signal amplifier, maybe you can adjust it. Rotate a tiny bit more clockwise. But this doesn't help if the input signal from ECU is not good. That's to be measured with an oscilloscope. Do you have a possibility to lend an oscilloscope?
its also possible the issue is with the cluster, if its a GTI you could check the MFA secret mode to see if the rev counter signal is being picked up by the trip computer https://www.clubgti.com/forums/index.php?threads/how-to-access-the-mfa-secret-menu.219196/
Good shout John. The digital rev counter drops with the needle, and constantly mirrors what the needles saying. If I put the headlights on and off it affects the displayed revs, not the engine revs tho. If I put elec windows up and down or put heater on it makes no difference. I guess it’s not volt drop in general, as not all loads seem to affect it, and revving the car to increase alt output makes no difference, but maybe whatever feed the adaptor is fed from is suffering volt drop under load with lights on? Need to see what else is on that circuit I think
is it a CE1 or CE2 fusebox? if CE1 the cluster earth runs to a male spade near the fusebox, make sure thats plugged in. originally the matching plug would be in the engien loom and runs off to earth on the block. if its missing you can just earth it to the claw above fusebox if its ce2 check g1/5 is earthed, but this isnt really all that important for the cluster
