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91 Merc. Capri Tachometer quit.


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Bigal12
New User

Nov 3, 2008, 4:14 PM

Post #1 of 2 (1053 views)
91 Merc. Capri Tachometer quit. Sign In

The tach started fluctuating for a while going up and down while driving and then just decided to stop all together. I'm sure it is electrical but don't know where to start looking. Thanks!!!


DanD
Veteran / Moderator
DanD profile image

Nov 6, 2008, 3:40 AM

Post #2 of 2 (1043 views)
Re: 91 Merc. Capri Tachometer quit. Sign In

I think you’ll have to go to the back of the instrument cluster and check for power, ground and tach signal. If you have all three, then the tach itself is the likely problem. Which means sending the cluster in and having it repaired; I don’t think the tack is serviced separately from the other gauges.
Looking at a wiring diagram; power & ground are probably ok, because the other gauges are functioning or at least you didn’t mention that they weren’t working.
The tach signal should be found at terminal 5 of the B connector; a yellow/blue striped wire. The connectors were usually labeled; if the connectors (A, B&C) are not labeled and according to the diagram I have; there is only one yellow/blue wire.
With the ignition in the run position, engine off, you should have ignition system voltage at this terminal. To compare what this voltage should be, take a voltage reading at the ignition coil’s negative terminal; it should be no more then a volt difference.

Dan.

Canadian "EH"










 
 
 






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