69 tach quit working

[Michael L.]

Guys,

I previously posted looking for a correct length tach drive cable for my 69. Now I'm concerned that it might not be the cable. I've disconnected the cable and the inner cable spins when the car is running so I know the tach side is working. I looked over the tach under the dash and the cable appears firmly attached. How can I troubleshoot this to see what the problem is?

Mike

[Paul D.]

Re: 69 tach quit working

More information will be needed for us to help. Does the tach show any movement at all? If not, try removing the cable from the distributor and spinning the cable with your fingers while someone watches for movement of the tach needle. Spin in both directions since spinning in the correct direction will cause more movement than the wrong direction will. If no movement is noted, focus should be placed on the distributer itself. With the cable removed, you should be able to see the gear with the square hole where the cable fits turning when the engine is running. If the gear is not turning, something is wrong in the distributer. The gear and housing it fits in can be removed to allow inspection of the gear. If the gear is all stripped looking, it is bad. Unfortunately, the distributer mainshaft is likely damaged also. Do the easy test first and get back to us. Chip.

[Michael L.]

Re: 69 tach quit working

Thanks. I don’t have a helper right now so I tried hooking up my cordless drill and there is no movement of the tach. I remember there was a stop on the inner cable that I think was located on the tach side that is supposed to prevent it from falling out on the distributor side but I can remove the inner cable as far as I want from the sleeve so I was able to plug that into the distributor and start the car and confirm the inner cable spins nicely so it’s not a problem in the distributor. I mentioned it in the other post but this is a recently completed restoration so the distributor and cables and everything are all fairly new. I’m starting to think that it’s the cable that’s wonky. On a recent restoration like this where the tach has worked for the last couple of years since getting the car running is there something that could go bad in the tach itself?

Mike

[Paul D.]

Re: 69 tach quit working

If you are saying you can pull the inner cable out from the distributer side, apparently the tip that fits into the tach has come loose from the end of the inner cable. On many cables, this tip is plastic and was held on by a glue that was activated by heating the cable and inserting it into the plastic tip. Unfortunately, you now need to remove the cable assembly to inspect. Watch for the tip to fall out when you disconnect from the tach or it may remain lodged in the tach. Chip.

[Michael L.]

[Bill B.]

Re: 69 tach quit working

Mike,

On my 1970 (suspect same for '69), the clip's tab must be pushed inwards towards the tach, then while holding the tab pushed in, the outer cable can then easily be pulled away from the unit.

[Michael L.]

Re: 69 tach quit working

Thanks Bill. I suspected as much after looking at a pic of back of a tach on eBay. I attached the pic for thread completeness's sake.

Mike

tach back.jpg

[Paul D.]

Re: 69 tach quit working

Bill is exactly right. In my experience, it is a one handed operation as space is limited! If you can get your hand into place, wrap your fingers around the cable and press the spring with your thumb. Hard (for me) to explain, but grasp the cable with your fingers pressing it against your palm and try to push the cable towards the tach slightly while pressing on the spring to release the cable. Once the spring is fully depressed, pull the cable away from the tach and you should feel it release. Try to note how the cable is routed before removing it so you can route it back in the same way. Not many options when routing that cable. I'm anxious to hear/see what you find when you get it out. Let us know and we can then discuss repair/replacement options. Chip.

[Michael L.]

Re: 69 tach quit working

Finally got back in the shop and pulled the tach drive cable out. I couldn't do the one-handed removal recommended by some, I managed get both hands up there and with a screwdriver I depressed the lock tab and pulled the cable out with the other. Before I did that I pulled the inner cable out from the distributor side and could see immediately that it was broken. When I got the rest of the cable out I found the other half. I ordered a new cable from the company someone recommended in another thread for replacement cables and I installed it and the tach is working perfectly. See the pic below of broken cable. Thanks for everyone's help.

tach drive cable.jpg

[Mike T.]

Re: 69 tach quit working

Michael - Glad you find the problem. Yours looks like a clean break. When I got my 66 L72 Roadster, the tach was inop and turns out it too had a busted drive cable but in my case, the cable had started to unravel before finally busting. Same result though, no tach operation.
IMG_9791.jpg