tach question

[j930]

what would cause the tachometer to not come alive when the engine starts? then just magically start working?

[unclebilly]

Bad ground. Check the connections on the back of the tach and then check the connections on the coil.

[TT Gasman]

Check the battery ground too.

[quattrorunner]

Mine does it when its hot. When it cools the inside of the cabin it starts again.

[Noah930]

If you check out those things and the tach still goes wonky, try putting a multimeter across the battery terminals when the tach's not working to see what voltage you're getting. (I jury-rigged a set-up with speaker wire from the battery terminals to my multimeter so I could see in the cabin what was going on while I was driving the car.) Depending on engine speed, it should be in the 13-14 volt range. But if it's not, you may be having an early problem with your alternator or voltage regulator.

[jsveb]

Originally Posted by quattrorunner

Mine does it when its hot. When it cools the inside of the cabin it starts again.

Mine does exactly the same thing.

[WilShel]

It happens to me too! My friend and Porsche mechanic for 45 years says to pull the tach and turn the glass around. he said when hot the glass warps enough to hold the needle. Once it cools the warp pulls back enough to let the needle go up again. I haven't tried to fix this yet but I will post back if I do.

[j930]

i know the battery ground is good as i just took it all apart. i will look at the connections on the back of the Gauge. interesting thoughts on the glass. voltage regulator is maybe 3K miles old and same for the alternator. The cabin was very hot and in direct sunlight. never had the problem when pulling out of the garage? i am thinking the glass theory might have some legs. switching that bezel is not easy. i had the speedometer worked on and watch the guy open it up. it was not super easy and i could see where you could easily wreck it.