Tachometer Bouncing
 

Yesterday my tachometer starting bouncing around in the 930. It will be fine for a while then suddenly bounce from 2K-6K-1K-4K ect. It then stops for a while and may start again. Any ideas of what may cause this?

Thanks
R

Does this happen while driving or while your sitting at idle? Does any of the lights come on when this happens?

I have only noticed it while driving. No lights come on.

Bad voltage regulator. Classic symptom.

Don't rule out a bad ground to the tach.

I second voltage regulator and add alternator failing.

I had the same symptoms, replaced the regulator only to have the alternator die two days later.

Time to change/rebuild the alternator...

Rig up a voltmeter to some handy place, like the cigarette lighter circuit, and take a drive. Have someone observe the voltage when the tach acts up. If the voltage goes up when the tach acts up, you will have confirmed a voltage regulation problem, as others have observed.

JR

Same problem with my 930 two years ago...bouncy tach. Checked grounding, all OK.
Shop checked voltage regulator, and replaced. No bounces for last two years.

I had this happen after I changed out dash lights...bumped wiring loose while I was in there. I would check those connections first.

edit: those= those on the back of the tach

Be careful....if the alt is over charging the battery will fry. If you start to smell sulfur or for us bay area folks a bay mud smell then water in the battery is cooking and could explode, or the smell could just make you sick. This happened to my carrera the battery was so hot that a meltdown was in process. Turn your lights on and see if they seem to be brighter another prob. can be radio static noise coming from you speakers when the radio is off.

check your system as soon as possible

voltage regulator..older cars like mine with ignition points will do it too when they get dirty or begin to close..but in your 930? VR..

ditto..get it fixed pronto..
ryan