68 Amp.Gauge Problem

[Mark F.]

I had the dash apart to replace a heater core and thought I'd replace the stuck amp. gauge as well. After I replaced the gauge and started up the engine, the gauge shows it's charging the system however the needle keeps bouncing. Once I rev the engine up to around 2200 RPM it settles down but as soon as I back off the RPM's it starts bouncing again. Any Ideas? 427 BB. I recently replaced the alternator and voltage regulator. Could this be that the voltage regulator isn't adjusted correctly or do I have a bad gauge?

Any ideas out there?

Thanks

Mark

[Lynn H.]

Re: 68 Amp.Gauge Problem

Mark,
Did you have the needle "bounce" before you replaced alternator and regulator, and did you replace both items at the same time? My thoughts are one of those items is extremely suspect, as being the cause of your situation. My first "guess" would be the regulator, but someone else may be familiar with this symptom, and have other ideas.
Lynn

[Paul H.]

Re: 68 Amp.Gauge Problem

Mark, If it's any consolation, my 68 big block's gauge operates exactly as you described. I have checked all the grounds/connections, replaced the voltage regulator, checked the alternator and belt tension as well as the battery and connections. I have no charging problems but the gauge has always bounced around unless I'm at a nice steady cruise. Then it settles down where you'd expect it to, just to the right of center. Probably the gauge.

[Terry M.]

Re: 68 Amp.Gauge Problem

I had the dash apart to replace a heater core and thought I'd replace the stuck amp. gauge as well. After I replaced the gauge and started up the engine, the gauge shows it's charging the system however the needle keeps bouncing. Once I rev the engine up to around 2200 RPM it settles down but as soon as I back off the RPM's it starts bouncing again. Any Ideas? 427 BB. I recently replaced the alternator and voltage regulator. Could this be that the voltage regulator isn't adjusted correctly or do I have a bad gauge?

Any ideas out there?

Thanks

Mark

Boy I would love to get an oscilloscope look at the 12 volt signal on these cars. Now days that tool is known as a lab scope. However, these are generally not the kinds of tools we have in our tool boxes. A skilled tech who works on modern cars will have one though. This is a place where a chapter might yield fruit in the form of what is known today as "networking."

[Dick W.]

Re: 68 Amp.Gauge Problem

Bad ground on the regulator will cause the problem you are describing

[Alan D.]

Re: 68 Amp.Gauge Problem

I had the same problem on my 1977. I sent the alternater to John Pirkle and he said it performed correctly. I made sure all the grounds were good and the printed circuit board was good. I also charged the battery for 10 hours and made sure the battery disconnect switch was making good contact. The problem went away. I believe that the battery was not up to a full charge and causing the problem. Note: That the problem would get worst at idle with the AC running. Just my experience.
Alan Dieterle

[Jim T.]

Re: 68 Amp.Gauge Problem

Bad ground on the regulator will cause the problem you are describing

Dick my 68's guage has the concerned movement sometimes. I am in the process of removing my radio for repair. I have plans to remove the wires to the guage and clean the terminals and wire ends. Will do the same for the gound wire for the regulator. It is all original equipment and has not been replaced or disconnected in over 42 years now.

[Mark F.]

Re: 68 Amp.Gauge Problem

I'll check the ground on the voltage regulator tonight.

To clear things up, the amp. gauge was stuck for many years as I didn't want to tear into the dash. I had a power drain back some time ago and thought it was the regulator so I replaced it with a new one (did no adjustments - just slapped it on). My alternator wasn't charging properly so I replaced it about a year ago. None of these contributed to the power drain (it ended up being that I was turning the key to the acc position). Guess I could always put the old regulator back on (actually I will some time as it's dated and the new one is not correct (repo).

Mark

[Rich G.]

Re: 68 Amp.Gauge Problem

My 68 BB amp gauge is steady as a rock from almost full deflection after start to just above zero. I agree a bad ground could be the problem, or it could be internal to the alt or regulator.

When my son was in college he killed the battery in the old Taurus he had there. Got ripped off by the local AAA afiliate who sold him a battery, alternator and regulator. After that, the lights would pulse from bright to less bright. I'm sure if there was an amp meter it would have been bouncing. Never did fix it.

Rich