Alternator
Thread Starter
Burning Brakes
Joined: Jul 2004
Posts: 1,192
Likes: 111
From: If your not the lead dog the view never changes Boise, Id
Alternator
I noticed in my 78 when I start the car the alternator does not come on line till I rev the engine to about 2200rpm. So I figure it is on its way out. I see alternators range from 45amp to 80 amp with the most common in local automotive stores at 65amp. I read on the forum here people putting in 200 amp alternators. I have an aftermarket stereo ( nothing fancy no amps or sub boxes) an aftermarket security system and a digital dash. How big an alternator should I buy? What did these come with stock?
Thanx
Thanx
Melting Slicks
Joined: Sep 2004
Posts: 3,225
Likes: 667
From: Northeast
"What did these come with stock?"
base 42amp
ac, rear defogger
61amp then 63 for later models.
I have an after market radio/cd player with amp and have been using a 63amp alternator without a problem. No ac however.
base 42amp
ac, rear defogger
61amp then 63 for later models.
I have an after market radio/cd player with amp and have been using a 63amp alternator without a problem. No ac however.
Last edited by BKarol; Feb 4, 2016 at 09:08 AM.
Thread Starter
Burning Brakes
Joined: Jul 2004
Posts: 1,192
Likes: 111
From: If your not the lead dog the view never changes Boise, Id
I have AC. When I start the car the voltmeter( digital) shows 11.7 volts if I don't rev the engine it will start to drop, early yesterday morning I started the car, and let it warm up with the defroster and headlights on. When I got into the car the voltmeter was at 10, I put the car into reverse and the radio shut down. I brought the RPMs up to about 2200 and the voltmeter finally started to climb, headlights brightened up, radio came back on. Once it comes on line the voltmeter will show between 14.3 and 13.6 at any rpm low or high.
Instructor
Joined: Jan 2012
Posts: 215
Likes: 6
From: Mebane, NC
re
Make sure the connections are clean and tight. Also if it is making good volts it might be the sensing function of the voltage regulator that is going south. You probably have an internal regulator, not that hard to replace, much cheaper than a new alternator.
Last edited by Capt Ken; Feb 4, 2016 at 10:29 AM.
Thread Starter
Burning Brakes
Joined: Jul 2004
Posts: 1,192
Likes: 111
From: If your not the lead dog the view never changes Boise, Id
How would I test the regulator. They are about one third the price of a new alternator but I hate troubleshooting by buying parts. If I do go with a new alternator Is there abenefit of going with an 80 or higher amp alternator, will it charge the battery faster?
Thread Starter
Burning Brakes
Joined: Jul 2004
Posts: 1,192
Likes: 111
From: If your not the lead dog the view never changes Boise, Id
Thanx Mike. I know how to test the alternator as a whole. It is not producing any voltage till engine RPMs hit around 2200 then it comes on and works as it should. I don't know how to test its internals separate from the whole. I'm guessing the guy behind the counter doesn't either....but I could be Wrong about that, I'll call and ask.
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Race Director
Joined: Apr 2007
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From: South Western Ontario
Replacing the alternator or regulator will just waste your money.
The symptoms you describe are the EXACT symptoms expected when terminal #1 on the alternator isn't getting power. Check the connector on terminal 1 and see if there is voltage with the key on. You should measure battery voltage with it disconnected and 2-3V with it connected.
Of course, you might have a 1-wire alternator installed. Is the 2-wire plug even connected to it?
Also,
A 78 should had a generator light from the factory.
The symptoms you describe are the EXACT symptoms expected when terminal #1 on the alternator isn't getting power. Check the connector on terminal 1 and see if there is voltage with the key on. You should measure battery voltage with it disconnected and 2-3V with it connected.
Of course, you might have a 1-wire alternator installed. Is the 2-wire plug even connected to it?
Also,
A 78 should had a generator light from the factory.
Last edited by lionelhutz; Feb 4, 2016 at 10:46 PM.