emac

Need a little help-- have a 81 911 sc and most of the time the tach works without a problem. However there are times that it just sits idle. I have taken it out and see no loose wires etc. and Im starting to think it may be a ground wire? If so where would I find this ground or could it be something else ?
Thanks in advance
Ernie

Toddimus

Same problem here!! I too have an '81SC. It seems that on hot days, the tach will sit at 0 for the first 5 minutes or so after starting. I've tried "flicking" the tach with my finger, and it seems to work sometimes. I think it's something in the mechanicals of the tach. Or it could be wiring from the CDS box? ...or who knows?? Tell me if you found a fix!

scottintx

I have had the same problem on a 78 911. I had it checked at a shop in dallas and the told me it it was just related to interior temp. After a couple of minutes of the AC on the Tach works fine. I have found a cracked window to do the trick on the hot parking days.

david914

If you've checked all of the exterior connections and found them to be OK, then open up the tach and look at the circuit board for cold (cracked) solder joints. Most of the time you'll find a solder joint that just needs re-flowing, especially around larger components.