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-   -   Tach not working (http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/129824-tach-not-working.html)

tclyder 10-01-2003 12:42 PM

Tach not working
 
I am in the process of replaceing all the guage faces with white guage faces and that is going great.

But I have a problem with my 1985 early 944's tach - it does not work The MPG guage works but not the tach

I bought another tach off of ebay and switched them and when the ignition is in the on position it reads 1000 rpm, off - 0

When the car is started i get nothing it stays at 1000 rpm.

the PO told me that he had the alarm disable and that would cause the tach not to work. He said a green wire was cut.

I have also read in other postings that if the green wire is cut in the alarm circuit it disables the tach.

Now that I have the tach out i can see the wires in the back and every thing looks fine.

I need to trace where this green wire goes to. I also know that the tach is driven by a timing pulse from the DME. Does this connection have a "Green" wire in it?

I want to make sure the tach works, either the one that came with the car or the one I bought before I take it apart to put the new face on it

Does any one have any idea as to where this "Green" wire may be cut? Does it go to the coil as well?

Thanks Tom

SoCal Driver 10-01-2003 12:46 PM

"Green" wire from the DME goes to the trigger (grounding) side of the coil and also to the tach. The alarm either grounds this wire or breaks the circuit.

If you car runs then the DME is controlling the coil. Need to find out where the wire to the tach splits off of the DME harness. This could be the location that the alarm is connected to.

tclyder 10-01-2003 04:20 PM

yeah! My tach now works!
 
I traced the green wire backwards through the wire harness through the firewall and along the front of the firewall right above the master break booster. I twisted the harness around and there right before my eyes was a green wire that was buired in the harness and it was snipped.

I spliced it together and now both my tach and my alarm now works.

The PO who sold me the car said he had the alarm disabled because he lost the key. I was lucky enough to have bought a brand new alarm switch with two keys and replaced it before.

So now I am happy and will replace the face of the tach with the white guage face.

I have been taking digital pictures of the guage face replacement and will be writing an piece for my local PCA chapter on how to do this.

Thanks for the help!

PS the other tach I bought off of ebay did not work - the one that came with the car did.

Tom


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