77 Tach filter
Thread Starter
Heel & Toe
Joined: Sep 2005
Posts: 18
Likes: 0
77 Tach filter
With my limited knowledge, I am guessing that the tach filters on 77's and other models are really capacitors. Since these filters are expensive (if they are what I think they are), I would like to know what value capacitor the filter is. If it's not a capacitor, what electronic component is it and what value?
When I got my 77 in August the tach didn't work. It worked very well when I by-passed the filter direct to the distributor. However, now that it has gotten cold, the tach is erratic until it warms up.
Please help me out.
When I got my 77 in August the tach didn't work. It worked very well when I by-passed the filter direct to the distributor. However, now that it has gotten cold, the tach is erratic until it warms up.
Please help me out.
Drifting
Joined: Oct 2003
Posts: 1,330
Likes: 1
From: Kerrville Texas
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
It is a capacitor. I did do some research one time on the cap value but don't remember the exact numbers but they're pretty expensive even if purchased from an electronic place as I recall. www.rodneydickman.com, Ecklers or Corvette Central wern't that far out of line. The thing acts like a filter and gets rid of the line spikes/overvoltages that the tach doesn't like.
Melting Slicks
Joined: Apr 2004
Posts: 2,083
Likes: 2
From: Montreal Qc.
Two capacitors and two resistors, parts are a few bucks at Radio Shack. There are bunches of schematics here in the archives, too bad they aren't searchable at the moment.
Anyway, ere's one from google:
http://temp.corvetteforum.net/c4/1mo...achfilterj.jpg
Anyway, ere's one from google:
http://temp.corvetteforum.net/c4/1mo...achfilterj.jpg
Racer
Joined: Nov 2004
Posts: 432
Likes: 0
From: Granbury TX
tach filter
My tach would stay high when the key was off so I removed the filter (located on top of the intake manifold, looks like a distrubuter condensor) and cleaned it real good with a wire brush and cleaned both connectors. It works great now. Sometimes a little cleaning works on these old cars.
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