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Strange tacho



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Dellb

Club Member

Thu 18 Oct 18 06:43

Strange tacho


Hi Guys
I seem to have a gremlin that I cannot track down. During the rebuild of my 1980 C3, when I had the dash out, I took the opportunity to replace the tacho board, and printed circuit.

During the build I changed the rad to aluminium with twin electric fans. I also upped the alternator to 110 amps.

When I turn on the ignition, the tacho goes to 0, telling me that I have 12V and earth.
All is fine until the fan kicks in. The tacho then becomes totally erratic and ending up at 7000. I am stumped. Any ideas?
Delb


--------------------
Derek L G

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kentvette

Club Member

Thu 18 Oct 18 11:44

Re: Strange tacho


As a "non-electrician" it sounds a bit like an earth problem.

But, one of the few things I do know about electrics is that the tacho circuit has a "choke" in it, (well it does in '78) located next to the distributor. In '78 there are, bizarrely, two plugs that are identical, one going via the "choke", one not. For a while, ours had the wrong one plugged in (not by me I should add!) and that did odd things to the tacho (it used to need about 30 miles running to get going!). The problem got noticed by chance at a transmission shop and they plugged the correct one in - no issues since. Just might be worth a look?


--------------------
Stephen J Irons
CCCUK Lifetime Member
Corvette Club France
Corvettes of Southern California
NCM Family Member
Stephen & June's Web Site
Red Corvettes Have More Fun!

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