Intermittent tach problem 1985
Thread Starter
Burning Brakes
Joined: Jun 2002
Posts: 1,001
Likes: 1
From: sd
Intermittent tach problem 1985
I have an intermittent tach on/off problem with my 85. Sometimes its on and sometimes it's not. Doesn't matter whether it's cold or hot or parked or driving. The contacts of the tach wire to the distrubutor are clean, wire is firmly in place, and no frayed or burnt wires. Any ideas? The Helm is of no use I'm convinced on some things and others it's a godsend but with this problem NADA for help. Thanks!!
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
go here, he has a diag for digi displays that just might get you going
http://www.batee.com/corvette/
http://www.batee.com/corvette/
Thread Starter
Burning Brakes
Joined: Jun 2002
Posts: 1,001
Likes: 1
From: sd
The gauges lite up fine all around. I can still see the increments for the tach such as 10, 20 , 30 and so on on the outside perimeter of the gauge itself. I'm just not getting any signal for RPM. I wonder if this isn't ignition module related as in a previous post? Thanks for the page though Vinnie!
Advanced
Joined: Apr 2006
Posts: 60
Likes: 0
The problem is your tach filter. Many people just remove it and the tach works fine but I don't recommend it because it's sole purpose is to shunt voltage spikes to ground which could damage your display. It is mounted on the intake manifold (at least it is on my 84) and looks like a small silver cylinder wired to your distributer harness. GM no longer carries the part but you can occassionally find them on Ebay. I bought one from a guy who makes them and sells them on his website. Do a google search for corvette tach filter and I think you will find him. It is a simple set up but for $25.00 it is well worth it. You can alo get them from Corvette Central on the web page but they charhe you a lot more.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
RRT has a tach problem also, I posted what Gordon Killebrew says in his book. Look up that post, maybe a few days ago. But, I will say this, Gordon says the most common problem with our tachs is water in the bulkhead connection, which is located by the steering column. The tach pin is located is in the lower row, the entire bulkhead connection is not sealed, making is prone for water leakage, plus the cowl drip tube may be directed right toward it.His cure, pull the bulkhead connection, it's full of a black grease-which is an anti corrosion grease, what you're looking for is a greenish/whiteish look, just blow it out, reconnect and use a sealer on the top and sides.
