Corellian Corvette

I'm having an interesting problem where the amp meter in my car is dancing around all the time.

What's interesting, is that it's not going "below" the charge line, but bouncing around above. This happens regardless of the rpm of the engine, or what accessories are on. I can have NOTHING running, and this still happens.

Here's what I've checked:

1. Visual inspection of the battery terminals (Battery is new Optima Red Top)
2. Visual inspection of negative battery cable (dirty but no splits, tight against the frame)
3. Replaced Alternator with new 63amp version. (old one was 55amp)
4. Visual inspection of alternator harness wires (nothing that isn't wrapped appears to be frayed or cracked), everything is bolted up tight.

The only thing that I wasn't able to check was the positive battery cable (since it's hidden), and obviously the harness going into the firewall since you can't really get to that without taking stuff out. I did do a good cleaning and all the wires appear to be OK.

Also, I noticed that there is some sort of silver soleniod on my inner firewall where the alternator harness connects. I assume it's some sort of voltage regulator. Do those go bad or could that be the cause of the problem?

Any help would be appreacited.

Thanks!

Smokehouse69

That silver relay is the Horn Relay. I have no idea where your problem is, but if you've checked everything else, it could be a loose connection behind you gauge.

Corellian Corvette

The horn relay? There are an awful lot of wires junctured there...

rainman69

First, double check the connections at the battery for tightness...that was my problem with my ammeter bouncing all over the place.

If that doesn't seem to fix it right off, get a partner and a DMM (digital mulitmeter), about 25 bucks from Radio Shack. Have the partner hook the positive test lead to the "batt" connection on the alternator, and the negative test lead to a good ground. Check for over 12V with the car off. Press the brake pedal, and make sure there is not a significant drop in voltage (approx 1-2V). Then start the car and make sure that the alternator is charging at about 14.8V and watch the meter in the car while the partner watches the DMM. Look for strange occurrences in voltage levels with that ammeter bounce.

As far as diagnosis. If the voltage drops significantly with the car off and pressing the brake pedal, there's a cut/cracked wire somewhere...

If it charges fine for a while and then kicks up to a higher voltage or does something strange, get the regulator tested. It's two parts, a diode trio and a bridge rectifier. The trio usually goes first. You can get this testing done with the alt. out of the car at an auto parts store.

Replace what is bad...Hopefully you'll have no more electrical problems. :smash:

VETDRMS

I've had this problem a few times, check the main battery terminal at the alternator, the internal nut can come loose and it will jump around, its a cheap fix, it could also be the internal regulator going out. My 160amp alternator went out on me, and in the process destroyed my wiring harness and about burnt my car up, so i would suggest taking care of this before driving much :)

Corellian Corvette

What's strange is that the alternator is brand new. I replaced it because the old one was doing the same thing. I think that eliminates the problem being the alternator. Also, I seriously double-checked the battery terminal connections -- in fact, the connectors themselves are brand new. (I replaced them when I replaced the battery)

Wierd.

rainman69

Then there's a broken wire somewhere...the casing may look fine, but the wire inside might not be fine. Lars can explain the procedure for finding the break.

Corellian Corvette

OK, did a couple of tests and I'm still confused.

I hooked the positive test lead to the "batt" connection on the alternator (green wire), and got 12.40V with the car off. Tested with the brake pedal, and voltage dropped to about 11.98V (is that OK?)

Then I started the car and it went up to 14.88V and jumped around between 14.7 and 15.4. Again, is that bad?

I also looked at the battery terminal voltage and it was the same (between 14.7 and 15.4)

So, again I'm still confused. I didn't think that guage was that sensitive but it really seems to bounce. Is that voltage jump normal?

WATTAC

Check your email. I sent a wiring diagram that I hope helps a bit.

If the output of the alternator is varying that much you may have an open "sense" wire. This is one of the smaller wires that plug into the alternator. Check for a loose connector or worn wires inside the connector. You may have to un-wrap the wiring harness between the alternator and the horn relay. Also check for loose connections at the relay. The diagram shows some "butt splices" that look like small black tubes with wires coming out of them. This is a splice that can open/break.

Proceed carefully. There's lots of un-fused power around this area coming from both the battery and the alternator. If you're even slightly unsure about the wires/wiring don't leave the battery connected until you find the problem.

Good luck,

Andy

woodworkr

Corellian
If the meter is dancing around and the needle is going rapidly back and forth the problem is the gauge itself. There is a small winding in the back of the gauge that is ready to give up the ghost. Same thing happened to mine. I called Gary Gurhala and got a new gauge from him for $25 end of problem. That is pretty common problem with the cardboard printed circut on the rear of the gauge. I don;t think that the circut is available seperately. And as an extreme case of the while you are in there, you may as well change all of the bulbs in the intsrument cluster.
Just my .02, worked for me,
JoeB

rainman69

It should not be charging at more than ~14.8V (the .88 is fine, but the >15 is too high). I'd suggest taking it to an Advance Auto Parts store and having them wheel the charging system/battery tester out to the car. Also, have them check the battery and alternator outside of the car to make sure it's good (on the special bench testers).

If that all comes up good, then start following that wiring diagram very carefully.

Corellian Corvette

I'm thoroughly confused at this point. I looked at the wiring diagram and traced down the wires. I replaced the contacts at the "Sence" wires, and found a "questionable" connection a little down the wires. Fixed that, and also removed the passenger side dash so I could see behind the guage. The wires look fine, and moving them around didn't do anything.

Also, one thing I should mention is that whenever I turn something on (lights, radio, etc.), the guage jumps as well.

Still -- I'm having the same problem. I'm going to try ordering a replacment guage. Would replacing the horn relay help?

Thanks

Corellian Corvette

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