Test Tacho how to?

[NeverEnough02]

Also, expansion tank is the rectangle on the drivers side. What does c104 look like? Is that the 3 wire plug pic you provided above?

[NeverEnough02]

Thank you for the help so far. Yes it is an 87 cabrio with an m50 swap done by the previous owner. I believe that box you referenced with the 3 plug is under the glove box ceiling right? I will have to take a look.

As for testing, here is what I did: set the multi meter to ac 20. Red lead to to black wire in the blue cluster group. Black lead to the neg battery terminal. Started it up and no signal. Was that the right method of testing with a mm?

[ForcedFirebird]

OP, here is what the c104 looks like:

http://s2.photobucket.com/user/bimster/media/host/labeledecuwires.jpg.html

To add: With a late model engine harness, the car will still start when the green wire is disconnected. If it has an early model engine harness the car will not start without the green wire plugged in as that's the power feed to the ignition coil.

[ForcedFirebird]

NeverEnough02's profile shows that he has an 87 325ic. Pages 6210-1 thru -5 shows that there is a Motronic on the I engines that feeds pin 7 on the cluster and yes it feeds through C104. I'm not sure what point you're making.

Just making it a point for people searching in the future who may come across this thread.

87ic will have the c104.

The OP even implied in the first post that he was told to check the c104 wiring which would mean early model wiring.

Easy way to tell (specially on cabbies as they were the chassis is always a year older than the hard tops) is to see where in the engine bay the expansion tank is. If it's on the passenger side and cylindrical, it will have the early model wiring.

If that c104 is unplugged or damaged, the tach and econogauge won't work. There also could be a late model engine harness installed which would require tapping in the ECU pin #6 for tach wired to the black c104 wire, pin #32 would need to go to the white wire - or - do it like the factory did for late models and run them through the c101.

[vpilarrt]

Only on late models. Early models have the three wire c104 connector next to the ECU plug that feeds the tach/econometer.

NeverEnough02's profile shows that he has an 87 325ic. Pages 6210-1 thru -5 shows that there is a Motronic on the I engines that feeds pin 7 on the cluster and yes it feeds through C104. I'm not sure what point you're making.

[ForcedFirebird]

Pin 7 (black wire) on C1 (blue connector) on back of cluster. Its probably a frequency variation or PWM (if they even used that on E30s) but I've checked this with a DVM (digital volt meter) before and IIRC the voltage reading will vary with engine speed.

Only on late models. Early models have the three wire c104 connector next to the ECU plug that feeds the tach/econometer.

[vpilarrt]

Pin 7 (black wire) on C1 (blue connector) on back of cluster. Its probably a frequency variation or PWM (if they even used that on E30s) but I've checked this with a DVM (digital volt meter) before and IIRC the voltage reading will vary with engine speed.

[NeverEnough02]

Hi everyone,


Tach and mpg do not work but I want to be sure they are getting a signal before buying a new SI or taking apart the cluster to re-flow. I have tried 2 clusters that I have with no luck.

How do you test the tach is getting a signal. I have searched for a few days and have not found any complete instructions. Some people say test plug 104c on the board but I do not know what method of test. ohms maybe?

Would like to test the wire going into the cluster if possible. Which wire would I test and what settings on the multi meter?