I Finished A Total Restoration On My 1968 Camaro And Lastly Installesd A Set Of Aftermarket Gauges. My Problem Is Two Fold;my Tachometer Works Fine For A Few Minutes And Then Zeros Itself Out And Doesnt Come Back Until Vehicle Is Restarted. Second Is My Volt Meter Reads 13.5 / 14.0 Volts At Idle,then As You Accelerate It Climbs To 16 Volts. What Should I Look For In These Two Problems? Thanks,smallblockmike

I would suspect a problem with the ground on the voltage regulator. Lack of a ground would cause the voltage to "run away"

I had this initially when I put my car back together, even though I did have the regulator's ground wire connected to the rad support. It turned out that the entire radiator support was "floating"" ungrounded due to all the new paint. Some star washers under some boltheads fixed it up.

Just to make sure the voltmeter is not off, does it read approx 12.5 without the engine running?

my Tachometer Works Fine For A Few Minutes And Then Zeros Itself Out And Doesnt Come Back Until Vehicle Is Restarted.

I am having this same problem, but the tach comes and goes (mostly goes) while driving the car. This original tach is securely connected to a new wiring harness and I have double checked the grounds and have them connected with star washers. Is there a screw connected ground point on the back of the tach that I can run a ground wire to? It's really hard to see back there.

Voltage problems could cause the tach to malfunction, though I've never seen this myself. Silicon diodes, for example, will break down once they heat up to a certain point. I'd follow Jim's advice and give the regulator circuit some attention. You should have no more than 14.5 volts.

On a separete note, lead acid batteries (not glass matt or gel types) should not exceed 16 volts under charge. If they do, it's an indication that the battery is "sulfated".

Where is the most logical place to put these star washers to insure a firm ground? My radiator support was powder coated which could be contributing to the problem. I may run a ground wire from the regulator to a solid ground point to test this theory.

When I had this problem, I just moved the lil ground lead off the battery cable to the rad support. If you want it stock, then put them under the fender bolts, and the inner fender to rad support bolts (from underneath)

To test for this particular ground, just use your voltmeter, one lead on the regulator case, the other either on the batter neg or the alternator case,m whichever is easiest to reach. Reading needs to be zero to be good.