Hello everyone. So ive had my 92 camaro rs 305 tbi t-top for about 1.5 years and have had a problem come up about 4-5 weeks ago. My voltmeter in the car would read at 14.2 volts and then randomly drop to 9-10 volts, all the lights would dim ect. I had the alternator changed with a 105 amp rebuilt from shucks auto. I also had the battery tested (it failed at 6 volts vs 12) and had it replaced. after having both of those replaced. my multimeter readings went up to 16.5 volts on idle then will (Not as often) randomly drop down to 14.2 volts but 80% of the time it Runs at 16.5. i tried turning everything off when the voltage was reading 16.5 and nothing happened. if im driving or not it doesnt seem to affect the voltage...

The 2 possibilities that i can think of #1 is that when i got the car the cooling fan motor would not kick on. so i have a small wire going going to that relay so that whenever i turn the key on the fan is running. But that has been like that for 1.5 years.. #2 is that i installed a stage 1 power chip about 2 months before all of this started happening.

any help would be great.

 

Do you have a good battery in the DMM? Sometimes a weak battery will show high voltage reading.

 

the batteries in the multimeter are good. i also had everything checked by the multimeter at shucks auto.

 

Then the first thing I would suspect is a poor ground. Likely culprits are between engine and chassis, between alternator and engine block, and possibly between battery and chassis.

I would also check the reference voltage at the connector at the back of the alternator. If there is high resistance in this circuit, or no voltage at all, the alternator will overcharge. If everything checks out, then it's the voltage regulator.

 

So from what I understand the voltage regulator is built inside the alternator. We checked the voltage between the negative lead on the battery and the red wire on the back of the alternator and it read 16.5 still and then will randomly drop to the 14.2. Sorry if I'm a tad slow with electrical I've never liked it and it frustrates the hell out of me lol.

 

Sounds normal to me. It won't stay the same all the time, goes up and down depending on what the electrical system is using. Cooling fans, blower motor, lights, anything.
Your gauges are old and not the most accurate either.

 

Over 16 volts is not normal.

The highest that should be seen is 14.4 volts.

Not the charge wire on the back of the alternator, but the sense wire in the plug, that is what gives the regulator the feed back so that it can control the voltage.

 

If he thinks it's over charging he should take it back or replace the voltage regulator in the alt.
Changing the potato in the tailpipe won't fix it.
Or he could use about 40' of wire wound up in the trunk from the alternator to the battery, voltage drop red neck style..
If If If he has his fan(s) wired to run all the time and one of the motors is bad, it could be straining the charging system and pushing the voltage regulator hard like that.

 

A proper diagnostic procedure goes through all of the possible reasons why something may be malfunctioning. The voltage regulator being faulty is not the ONLY reason to have high voltage, it's likely, but not the only reason. For a voltage regulator to function properly it must have a good reference to ground and to a reference voltage, if either of these are not correct, the voltage output can be incorrect.

 

Thank you Six_Shooter for the help!! I checked the reference voltage at the connector at the back of the alternator and everything checked out good. I changed the alternator for the third time and everything is working just fine