Hi everyone, here is my problem. My car stops charging once it reaches normal operating temp. The alternator dips really low in volts.

I am positive it isnt the alternator, I've replaced it twice in the past month with brand new ones. I had an aftermarket chip in place, I removed it but the problem persisted. Yesterday, I went and bought a new ECU. Thought the problem was fixed, but it came back. What could cause this charging problem?

By the way, I cant tell if its throwing any codes. I removed the airbag (replaced steering wheel)and the "service engine soon" light was constantly on so i disconnected it at the time. Plus, I dont have an auto-xray or anyhing.

Any ideas? The battery is new as well...

This is a 92 305 TPI G92

 

How are you checking the volts? Are you looking at the factory gauge? Is the car losing charge to the battery? I have to smack my factory gauge from time to time to get it to read right...check it with a voltmeter and see what you get.

 

GM cars are famous for lower voltage indicated on the dash when things get nice and toasty under the hood. It can get down as low as an indicated 12V! I don't know why this happens but it's not harmful and it doesn't mean it's not charging. I think it's just where they hook up the wire to get a voltage reading is very temperature sensitive.

My 94 Firebird (with 140 Amp alternator) will indicated 15V on a cold morning afterstartup but only 12.5V on a hot summer day with the engine fully warmed up. All my GM cars have this "problem" in some form or another. I consider it weird but normal.

 

the car battery actually gets completely discharged if I do not stop driving it and cool it down!

I am clusterfcked as to what this could be . any ideas?
thanks guys

 

Check the power wire connecting the alternator output to the battery. Check for bad connections at the batt and alt. Look for any repairs (splices) in the wire.
Bad connections (and bad corroded repairs) will get worse as the temps increase.

My wifes' car (Volvo) had a samiliar problem. I cleaned the connections and inspected the wire, but it looked fine. I finally disconnected the original main power wire at the alt and made my own wire to connect the batt to alt.

This wire carries a lot of current. I originally used 18" of 10-gauge wire. It got hot after a few mins. with all the accessories on.
I added another 10-gauge wire so I have 2 and it works fine now.
If running only 1 wire, use 6-8 gauge wire.

Be sure to disconnect the neg batt cable before doing any of this.
Be sure to terminate the original alt wire so it doesn't touch anything. I taped and ty-wrapped mine so it wouldn't short-out.

 

Thanks man! that was the problem. I remembered I re-located the battery (after s/c install) and had to extend the wire. I used ****ty connectors. So i took it out and soldered. Fixed!
Thanks!

 

Here is my charging problem story. After new engine I've gone through two alternators and a few batteries. I always suspected crappy reman alternators because my guage would drop to about 9 volts while driving, then go back up. Frequently it hit 8 and I would freak out, thinking another alternator was bad. I leave the car sitting for two days and the battery is almost drained, hmm.. I check the voltage at the battery with the car running - 13.8v, 14.8v at the alternator. However, the factory guage is saying 10 and moving around, even though the output is normal. I install a switch to d/c the battery when the car is shut off.

My conclusion: the factory guage is a piece of **** and is completely inaccurate, at least in my case. I have a power drain when the car is turned off that is killing batteries, but until I find it my fix is sufficient.

Don't believe your factory guages!

 

hey rezinn, in my case ...the battery would drain when driving. Meaning the factory gauge was accurate.

I found out the problem. Bad connection