I've been having some trouble with charging system. Its a carbed LG4, so when I cold start it idles to 2000 rpm, where the voltage jumps to over 15V according to the gauge. I've verified the gauge is close to actual with a DMM. Once its warmed up the voltage comes back down to 14.5V. But it has tripped a trouble code 53 twice already. This alternator is a reman, only a couple months old. The last one had a blown regulator, always charging at 16V or more. When I put the new alternator in I had AutoZone check my battery, they said it was good, but had a low charge at the time. I'm not sure, do I need a battery even though AZ says its good? Its a couple of years old, but sat for awhile.

 

Don't know if I am any help here, but it is much more destructive to a battery to have an overcharge condition than to have an undercharge. You said that when it's cold the alt charges to 15 right? That might be because the old alt damaged the battery(16V) and cold weather is hard on battery's in the first place. Even a new battery off the shelf will drop about a half a volt in cold weather. 14.5 volts isn't an issue, so I wouldn't be too worried. The 15 volts is a little high, but I really think it's due to the alt overcompensating for the failing battery.

 

Yea thats what I was thinking, maybe the battery's on its way out, but do you think Autozone's equipment isn't good enough to see it? I'm going to try to borrow someoneelse's battery and see if the same thing happens.

 

it is quite possible the test equipment autozone is using shows the battery as good when it really is bad. it isn't so much if their equipment is good enough, sometimes the new electronic testers miss things.
where i work at we have a Snap On MicroVAT which runs about $1000.00, but from time to time i still have to bring out my 30+ year old manual load tester, volt meter & amp meter to verify if a battery is actually able to perform like it should.

 

Only in diesels with dual battery setup have I seen the batteries being able to hold down the charging voltage for a while after starting. The battery cannot be held responsible for overvoltage from the alternator, no matter how bad it might be. The alternator has the amps to do what it wants with the voltage. I have seen some alts give a higher voltage until they warm up. I don't know if this is intentional or due to bad design. If the alt has a remote voltage sense wire in use, then a bad connection somewhere can make the voltage go higher in another place.
Anyway, the most sensitive stereo I've seen had a 15.4 max voltage input spec. and in cold weather (-5 celsius) 15V is actually the correct charging voltage for the battery, and nothing will be damaged by this except 100W headlight bulbs which do burn out faster..

 

trumps2000, code 53 doesn't show up in my books for a 85 Camaro, it does show up for an 86. it shows as a problem with EGR control with a carbed motor. for a FI motor it shows as voltage greater than 17.1 at the ECM for more than 2 seconds.


most of the time a bad battery will just burn out the alternator & cause a no charge.
i have seen bad batteries damage the alternator & cause an over charge problem, maybe the regulator was weak to start with on these cars.
i have also seen a few batteries with a much higher than normal voltage after they were damaged by an over charging alternator, the worst one produced 15 volts after sitting for about an hour after the load test. that car had a charging voltage of 18 volts at 1500 RPM. it is rare but does happen.

 

The ECM in my car is from a later model LG4.

I must be missing something though, because this alternator is a new reman, the battery supposedly checks fine, I cleaned all the connections, and it only does this while warming up.

I'll try borrowing my roommate's battery and see if it does it then, otherwise maybe I need another alternator.

 

Well I tried that new battery in the car and it overcharges even then. I did verify that on a warm start the voltage goes right to 14.5V. I'm stumped.

 

if you haven't already, with it cold check the voltage of the wiring at the connectors at the alternator with the key on & the off engine like Fullsizewagon said. i believe they should all show very close to battery voltage with them unplugged from the alternator.
if they check good, get another alternator.

 

I finally fixed the problem. Turned out to be a bad alternator. Though I haven't put any miles on it yet, its been working great so far. Thanks for the help guys.