Tach issue
Thread Starter
Intermediate
Joined: Aug 2006
Posts: 47
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From: MS
Tach issue
Please clue me in on this problem. 1973 L-82, start car and all is well tach functions normally. After a few minutes (let's say 5-10 min.) when the car gets warm the tach goes to zero and stays put for the duration of the drive. Turn the car off and it cools down, restart the car, tach is normal again. The cycle continues, the car runs fine and no issues are experienced when the tach goes to zero. Any suggestions? Thanks in advance.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Interesting to say the least! The problem could be several things.
On replacement tach cables the end of the cable may have a plastic end. This end may be loose and only working when it’s cold.
The tach first worm and magnet bushing may be bad and when it heats up it may be shrinking down on the first worm and locking it up.
It could be a problem in the distributor gears.
My suggestion: Drive the car until it heats up and stops working. Un-screw the tach cable from the distributor and hook a drill up to it. See if the tach works with the drill. If it works, you know the problem is in the distributor. If it fails, the problem is in the cable and/or the tach.
Next if the problem is not in the distributor, repeat your drive and get the tach to fail again. Pull the tach cable off the back of the tachometer and see if it is spinning with the distributor. Inspect the end of the cable and see if this is your problem. If not, then you have a problem in the tachometer and it will need to come out of the car. We repair these in house and have 24 hour turn around on them should you need it repaired.
Willcox Inc.
On replacement tach cables the end of the cable may have a plastic end. This end may be loose and only working when it’s cold.
The tach first worm and magnet bushing may be bad and when it heats up it may be shrinking down on the first worm and locking it up.
It could be a problem in the distributor gears.
My suggestion: Drive the car until it heats up and stops working. Un-screw the tach cable from the distributor and hook a drill up to it. See if the tach works with the drill. If it works, you know the problem is in the distributor. If it fails, the problem is in the cable and/or the tach.
Next if the problem is not in the distributor, repeat your drive and get the tach to fail again. Pull the tach cable off the back of the tachometer and see if it is spinning with the distributor. Inspect the end of the cable and see if this is your problem. If not, then you have a problem in the tachometer and it will need to come out of the car. We repair these in house and have 24 hour turn around on them should you need it repaired.
Willcox Inc.
