Rev counter wiring

[sk712]

Hi,

I have narrowed down my non working tacho to the wiring. I have read that the connection on the c101 plug may cause a problem. All I have done is wiggled it & disconnected it a few times. The pins all look fine. Is there any way of testing it? Also could there be a fault in the ECU or is there another place the wiring can cause trouble? I really hate electrics so any help would be much appreciated. Clocks, SI Board, fuses are all fine. I think the car wont run if engine speed sensor is shagged so I presume thats not the problem.

Thanks

[sk712]

Ok, I have continuity between pin 6 on the ecu & pin 7 on the blue plug that goes to the cluster. Is there anything else that could be causing this? Clocks worked perfect on another car yesterday.

[Brianmoooore]

Is there anything else that could be causing this? Clocks worked perfect on another car yesterday.

In a word, no, there isn't anything else. The only connectors the signal goes through are the ECU plug, the C101 and the plug on the cluster.
Have you tried the "another car"s clocks in your car?
I've seen cracked solder joints on the pins of the sockets on the cluster, caused by someone trying to force the plugs out without releasing the locking bar. Unlikely to be your problem, but it's the best I can do at the moment.

[sk712]

Yeah tried the other cars clocks in my car & the rev counter wouldn't work. Would the ECU be at fault?

[Brianmoooore]

Not a known fault, but it's possible. There is a buffer inside the ECU, part of IC S600, plus a diode and a couple of resistors, shaping the raw signal, and, being electronic components, can fail.

[sk712]

Thanks Brian. Might try that.

[sk712]

Just tried an ECU from another car & it didn't sort the problem. Is there anything else that could be tried?

Thanks

[Brianmoooore]

There's nothing much else it can be - it's just a single wire from the pin on the ECU to the pin on the cluster plug, passing through the C101 on the way.
You say you've checked for continuity. Have you checked for insulation with both the cluster and ECU unplugged? Connect your meter, on its highest resistance range, between the wire and earth. Reading should stay at infnity.

[sk712]

Checked for insulation. Ran a wire from ECU to cluster direct just to be sure but no joy. Stumped.