Alternator and tach issues.
 

Ok so some weird stuff is going on with the alternator in my car just seeing if someone can help me figure this out. I have a euro '80sc, when im driving, the alternator seems to kick out (generator light comes on and my lights dim) andthe seat belt light comes on. This seems weird to me. The belt isnt slipping, ive already confirmed that. But another really weird thing that happens is the tach just starts going crazy! The needle bounces up and down. This normally happens when everything else does but sometimes it will bounce around randomly. Any ideas?
Thanks, miles

Per North Hollywood Speedo, you can start by replacing the voltage regulator.

I had issues with my '84's tach, and this was one of the suggested starting points. As it turned out on mine though, it was a bad tach.

Good luck!

My "crazy tach" seemed to be a symptom of the alternator finally giving up. Battery was DOA 20 miles later.

Seems to me the alternator rebuild was about $100 and the HUGE Diehard from Sears about the same.

Was a good opportunity to see what's behind the fan. Actually polished the fan, which stayed polished about 20 minutes. Also discovered the "air channel gizmo" behind the fan was broken and needed R & R. Always good to keep digging with these cars to fix more broken stuff.

Haha that is for sure about the digging to find more stuff. But thanks, ill pull the alternator and get it checked out and ill replace the volt regulator.

I had the same problem with the tack bouncing all over the place at random in my 77 euro SC. Solved it by replacing the regulator in alternater

I dunno if they're the same, but I kept the good one from my '84 when I replaced it, trying to troubleshoot the tach issues I had.

Check your battery too, make sure you haven't overcharged it. When I replaced the alt, I replaced the battery too. Of course, it was a $330 alt at the dealer back then, now they're like $600+ I think.

I also kept my old bad alt, never did get it reman'd though.

Put a voltmeter on the cigarette lighter wire while you drive. Report back with min and max readings.

Voltage regulator.

But check battery first.

Some may say that if your VR fails that your alternator is next. I replaced my VR nearly 2 years ago. A couple of months ago I had my alternator bench tested and it checked out ok.

VRs are cheap too.

Just solves this EXACT problem!

+1 on checking the voltage through the cigarette lighter.

Easy fix... rebuild the alternator. My rebuild one just arrived in the mail today (I'm running on a replacement). $130 plus shipping.

A short in my alternator was affording the occasional 18V surge that whacked everything out just as you describe.

Good luck!

Awesome guys! i appreciate it. But yeah im goona check the volts with the cigg lighter tester and check the battery also. It would probably be beneficial to install a volt gauge down the line. What kind of numbers do i need to look for? I wont be able drive the car until this weekend

I think you should be in the 13.7-14.0 Volt range if it's under control.

My voltage spiked when the VR started failing.

Funny about the cigg lighter. I had my VR-1 radar detector plugged it and it was the first to start acting funny. Then the tach followed.