Charging
Thread Starter
8th Gear
Joined: Aug 2007
Posts: 8
Likes: 0
From: Naperville Illinois
Charging
I amstill having the same roblem with my charging system. I have done everything, put a 120 amp alt on with a smaller pulley and that brought the charge up to 14.0 at an idle in park which was never there. Had my alt builder beef the 120 up even more than it normally is but at an idle in drive I still drop down to 11.5. I own an auto shop and me and my guys are pulling our hair out over this.
Does anyone have any advice on this or has seen it in the past? Any help would be appreciated.
Thanks
Bill
Does anyone have any advice on this or has seen it in the past? Any help would be appreciated.
Thanks
Bill
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
I'd guess that the idle output remains low - you could measure it with a clampon meter or slowly turn on accessories, such as the a/c, while monitoring voltage. That, on high blower, can suck 25 amps, your fan another 10 and by the time you've turned on the lights and radio, the alternator is tuckered out. Your gage may not be accurate either. It's reading system voltage via the ignition switch then through a fuse and onto the panel. To check it, it's easier to drop the steering column, then measure the input and outputs to and from the switch. I got .6 volts back at the Display by simply cleaning up the contacts. That input also comes through the big connector behind the battery, so if it's weak, there may be some corrosion in there. GM will tell you that what you're seeing is normal and issued a Bulletin (back in the '90's) telling the Dealers they wouldn't be reimbursing them for alternators if the only problem was that the car couldn't get above battery at idle (actually, since few of their cars have a voltimeter, customers were complaining about the lights and dashes dimming at idle).
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
Motor City Reman recommends upgrading the wiring when going to a high output alternator. That makes sense to me. You can go to their site for info.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Put a voltmeter on the battery. Engine cold, idling, you should see 14.7 volts, in park the engine idle rpm should be about 800 rpm. Engine hot, the alternator output falls to 13.7 volts across the battery. Compare the voltmeter across the battery with the dash voltmeter, the dash meter might be reading low (0.3 volts lower than battery voltage is normal). Compare the voltage from the battery positive terminal (engine idling) and the alternator output terminal, they should be identical. Higher than about 0.1 volts on the alternator output shows a defective fusible link in the alternator output wire and it should be replaced.
Last edited by jfb; Oct 19, 2007 at 11:27 PM.
Thread Starter
8th Gear
Joined: Aug 2007
Posts: 8
Likes: 0
From: Naperville Illinois
Done all
Put a voltmeter on the battery. Engine cold, idling, you should see 14.7 volts, in park the engine idle rpm should be about 800 rpm. Engine hot, the alternator output falls to 13.7 volts across the battery. Compare the voltmeter across the battery with the dash voltmeter, the dash meter might be reading low (0.3 volts lower than battery voltage is normal). Compare the voltage from the battery positive terminal (engine idling) and the alternator output terminal, they should be identical. Higher than about 0.1 volts on the alternator output shows a defective fusible link in the alternator output wire and it should be replaced.
Bill
Advanced
Joined: Sep 2007
Posts: 59
Likes: 0
From: Spring Hill Florida
I was losing a full amp from the alt to the battery. Would get like 14.2 at the alternator, and 13.5 at the battery, and finally 13.2 in car. Took the battery out, and the tray under it, cleaned and redid both grounds under there and now Im close to even all the way around! Free to try, cant hurt!
