1980 L48 tach problem
Thread Starter
1st Gear
Joined: Sep 2005
Posts: 1
Likes: 0
1980 L48 tach problem
Hi there,
been lurking for awhile around here. nice crew. Figured I would post this because I can't seem to figure it out.
I have no reading from the tach. It just sits at zero. I looked at the schematic in the shop manual, but nothing really to guide me. Where does the tach receive the reading?
Any help what so ever would be greatly appreciated.
Michael
been lurking for awhile around here. nice crew. Figured I would post this because I can't seem to figure it out.
I have no reading from the tach. It just sits at zero. I looked at the schematic in the shop manual, but nothing really to guide me. Where does the tach receive the reading?
Any help what so ever would be greatly appreciated.
Michael
Melting Slicks
Joined: Apr 2004
Posts: 2,083
Likes: 2
From: Montreal Qc.
Lots of threads here on tach fixing, here's the most recent with some good info on the workings/parts/etc of electric tachs
http://forums.corvetteforum.com/show....php?t=1167061
http://forums.corvetteforum.com/show....php?t=1167061
Drifting
Joined: Nov 2003
Posts: 1,634
Likes: 4
From: Northern NJ
St. Jude Donor '04 & '05
Welcome to the insanity! 
You can also check the tach filter which should be inline between the distributor and the tach. Usually located at the rear of the intake manifold, drivers side. It's a round metal can, similar in appearance to a typical noise filter cap, with a wire at each end. You can try bypassing it to see if the tach starts working again. If so don't leave it like this as you could damage the tach board w/electrical spikes if it's not in place. If you need a replacement, don't need it to be original and are handy with a soldering iron, I can provide a schematic of the 4 parts (two resistors, two caps) needed to construct one. Just let me know.
Now all that said, it is just as likely, if not more so, that the circuit board on the back of the tach could be bad too. Troubleshooting this is more of a eliminate everything else and if it still doesn't work, then purchase a new board and replace it.
Of course the first thing you should probably do is make sure all your wires/connections are in place, are hooked up and, have continuity. Should go from the tach output on the distributor, to the tach filter, thru the firewall to the tach board.
Hope this helps. Don't hesitate to ask any other questions if necessary.
Good Luck!
You can also check the tach filter which should be inline between the distributor and the tach. Usually located at the rear of the intake manifold, drivers side. It's a round metal can, similar in appearance to a typical noise filter cap, with a wire at each end. You can try bypassing it to see if the tach starts working again. If so don't leave it like this as you could damage the tach board w/electrical spikes if it's not in place. If you need a replacement, don't need it to be original and are handy with a soldering iron, I can provide a schematic of the 4 parts (two resistors, two caps) needed to construct one. Just let me know.
Now all that said, it is just as likely, if not more so, that the circuit board on the back of the tach could be bad too. Troubleshooting this is more of a eliminate everything else and if it still doesn't work, then purchase a new board and replace it.
Of course the first thing you should probably do is make sure all your wires/connections are in place, are hooked up and, have continuity. Should go from the tach output on the distributor, to the tach filter, thru the firewall to the tach board.
Hope this helps. Don't hesitate to ask any other questions if necessary.
Good Luck!
Last edited by ACECO; Sep 21, 2005 at 09:50 AM.
Burning Brakes
Joined: Jun 2005
Posts: 764
Likes: 2
From: THE OLDER I GET THE BETTER I WAS! NORTHERN ONTARIO
I could sure use the schmatics for that tach filter as my 79 did not have one when I bpught the car. Thanks. my e mail bpischlar@ctv.ca
Le Mans Master
Joined: Jan 2003
Posts: 6,575
Likes: 1
From: Tuttle OK
Cruise-In VIII Veteran
Originally Posted by G dad
I could sure use the schmatics for that tach filter as my 79 did not have one when I bpught the car. Thanks. my e mail bpischlar@ctv.ca
Click here...
Burning Brakes
Joined: Jun 2005
Posts: 764
Likes: 2
From: THE OLDER I GET THE BETTER I WAS! NORTHERN ONTARIO
Originally Posted by Avette4me
This guy did one hell of a job posting good info. It's on an '80, but I'm sure that most will help you on your '79...
Click here...
Click here...
Drifting
Joined: Nov 2003
Posts: 1,634
Likes: 4
From: Northern NJ
St. Jude Donor '04 & '05
Just in case anyone needs a copy, I'm posting the tach filter schematic here for reference. I'll be away most of the weekend at the NJ leg of the Tuning for Beer tour and probably won't be checking the forum until at least sunday.
Hope this helps someone.
Hope this helps someone.
Last edited by ACECO; Sep 22, 2005 at 09:39 AM.
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