74 coupe, tac went out
04-09-2014, 12:52 PM
#1
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Member Since: Dec 2012
Location: Streamwood IL
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74 coupe, tac went out
Can anyone get me started on what to look for first. Tac was working fine one day, then the next day got crazy jumpy until it just stopped.
04-09-2014, 12:57 PM
#2
Le Mans Master
The other possibility is that the cable itself is broken or the tach mechanism itself died. To test it, get a portable drill and put the cable end in it and with somebody in the driver's seat, see if putting any RPM's to it, makes the tach needle move. You might have to experiment with what direction it turns (clockwise or counter-clockwise) to get results, but one of those two, should get you something.
04-09-2014, 02:51 PM
#3
Pro
If you have the original mechanical tach, you'll have to pull the tach cable, where it attaches to the distributor. It may be as simple as tightnening up the outer ring if it's loose, or it could possibly need some lubrication (that's why they jump around, the cable is binding and twisting inside the housing).
The other possibility is that the cable itself is broken or the tach mechanism itself died. To test it, get a portable drill and put the cable end in it and with somebody in the driver's seat, see if putting any RPM's to it, makes the tach needle move. You might have to experiment with what direction it turns (clockwise or counter-clockwise) to get results, but one of those two, should get you something.
The other possibility is that the cable itself is broken or the tach mechanism itself died. To test it, get a portable drill and put the cable end in it and with somebody in the driver's seat, see if putting any RPM's to it, makes the tach needle move. You might have to experiment with what direction it turns (clockwise or counter-clockwise) to get results, but one of those two, should get you something.
04-11-2014, 02:21 PM
#4
Do the troubleshooting recommended with the drill first. If the needle moves smoothly then the likely cause is damaged gear teeth on the main shaft inside the distributor. To repair you will need to pull the distributor and have the main shaft replaced. If you have the work done then the cost will be around $200.00 including the cost of the shaft.