Tach does not work on real cold mornings
Thread Starter
Heel & Toe
Joined: Mar 2005
Posts: 17
Likes: 0
From: DeFuniak Springs FL
Tach does not work on real cold mornings
82 Corvette. During the recent cold weather we are having here in the panhandle of Florida, I noticed my tach needle not moving when car is first started. After the car warms up, the needle will move (tach reads a little high normally) and it will operate as usual. Bad cable, need cable lube, etc.? Any help will be appreciated.
Dan
Dan
Race Director
Joined: Oct 2000
Posts: 12,683
Likes: 3,135
From: Shamong, NJ
The panhandle doesn't get cold, it was 13 degrees here (NJ) this morning.
82's don't have a cable, the tachs are electronic. Not sure exactly what would cause your tach to be slow to operate, but problems with 75-82 electronic tachs can usually one of two things. These are the tach filter or the circuit board in the tach.
The circuit boards are available for about $60 from most parts vendors and come with instructions on how to recalibrate your tach when done installing the board. The tach needs to be removed from the dash to install the board, but it's a pretty simple task. Replacing the board will probably fix your accuracy problem. The tach filter is found under your hood, on the right side of your engine, near the distributor. Repros of these were supposed to be in the works, but I don't know if they're on the market yet.
Someone on the forum with more experience with automotive electronics, may be able to help you further.
82's don't have a cable, the tachs are electronic. Not sure exactly what would cause your tach to be slow to operate, but problems with 75-82 electronic tachs can usually one of two things. These are the tach filter or the circuit board in the tach.
The circuit boards are available for about $60 from most parts vendors and come with instructions on how to recalibrate your tach when done installing the board. The tach needs to be removed from the dash to install the board, but it's a pretty simple task. Replacing the board will probably fix your accuracy problem. The tach filter is found under your hood, on the right side of your engine, near the distributor. Repros of these were supposed to be in the works, but I don't know if they're on the market yet.
Someone on the forum with more experience with automotive electronics, may be able to help you further.
Safety Car
Joined: Nov 2004
Posts: 4,359
Likes: 57
From: Mundelein Illinois
I had the same problem. I removed the tach and took a small sodering iron and heated all the soder points on the board. I must of had a cold soder joint somewhere, because it fixed the problem. You can try this but you may have to replace the board.
Tack is electronic/Speedo is machanical
Hope this helps
Tack is electronic/Speedo is machanical
Hope this helps
Thread Starter
Heel & Toe
Joined: Mar 2005
Posts: 17
Likes: 0
From: DeFuniak Springs FL
Thanks for your help. What is the best and easiest way (if there is one) to remove the tach to get to the board? I can touch up the solder joints with no problem. Anything else I need to know or do?
Hey, I know Jersey is cold! I spent time at Naval Weapons Station-Earle. I know all about the cold weather up there.
Dan
Hey, I know Jersey is cold! I spent time at Naval Weapons Station-Earle. I know all about the cold weather up there.
Dan
Safety Car
Joined: Nov 2004
Posts: 4,359
Likes: 57
From: Mundelein Illinois
Thanks for your help. What is the best and easiest way (if there is one) to remove the tach to get to the board? I can touch up the solder joints with no problem. Anything else I need to know or do?
Hey, I know Jersey is cold! I spent time at Naval Weapons Station-Earle. I know all about the cold weather up there.
Dan
Hey, I know Jersey is cold! I spent time at Naval Weapons Station-Earle. I know all about the cold weather up there.
Dan
Remove 4 screw in panel under steering column and loosen the 2 bolts that hold up the column. This will allow the steering column to lower which will be eaisier to remove.
Remove screw that hold speedo and tach to dash
Disconnect speedo cable and pull guage section out and disconnect electrical harness at back of cluster.
Remove lense cover
Remove black allen screws to remove black facia
Remove 2 or 3 three screws that hold the tach to the cluster (back of cluster)
Remove nuts that hold circuit board to tach.
Melting Slicks
Joined: Sep 2004
Posts: 3,227
Likes: 670
From: Northeast
I started to have the same problem last year and it is definately not my tach filter since I havent had one for years.
On my 78 I anticipate using this write up for 75-82 tach board removal. Appears to be different than Spedaleden. Perhaps it is not correct for some years? Good luck.
http://www.corvettemagazine.com/2005.../tach-lead.asp
On my 78 I anticipate using this write up for 75-82 tach board removal. Appears to be different than Spedaleden. Perhaps it is not correct for some years? Good luck.
http://www.corvettemagazine.com/2005.../tach-lead.asp
Safety Car
Joined: Jun 2004
Posts: 4,372
Likes: 223
From: Beecher Illinois
I started to have the same problem last year and it is definately not my tach filter since I havent had one for years.
On my 78 I anticipate using this write up for 75-82 tach board removal. Appears to be different than Spedaleden. Perhaps it is not correct for some years? Good luck.
http://www.corvettemagazine.com/2005.../tach-lead.asp
On my 78 I anticipate using this write up for 75-82 tach board removal. Appears to be different than Spedaleden. Perhaps it is not correct for some years? Good luck.
http://www.corvettemagazine.com/2005.../tach-lead.asp
On my seldom driven 78SA the tach seemed stuck. It was. Took the clear lense off in preparation for tach removal but gave the needle a nudge first.
Works fine now! The needle is very sensitive. I believe I once heard someone refer to it as a fluid drive(?).
I DID need to replace boards in 2 other Vettes. Both had bad chips and weren't repairable. Member Aceco repairs boards if the chip isn't fried.
Last edited by KapsSA; Mar 5, 2009 at 03:16 PM.
