Need Alternator GURU---Help
Thread Starter
Racer
Joined: Sep 2007
Posts: 493
Likes: 0
From: Eden Utah
Need Alternator GURU---Help
My Alternator went out on my 85 C4 leaving me stranded 40 miles from home, I am 71 years old so I was not too happy. My son brought me a new one, I installed it, and nothing showed up on the volt meter. I got the car home, Put it up on blocks and started chasing wires. All of the major wires from the battery to the starter looked good and have continuity. The main wire to the alternator has 12 volts when I check it with the multi-meter. Took the alternator off and too it to O Rileys, put it on the tester and it check out good. When I put it on the car, it only shows 12 volts going to the battery...
What am I missing, why is the alternator not working on the car. Need help please....
Wayne
What am I missing, why is the alternator not working on the car. Need help please....
Wayne
Instructor
Joined: Jun 2011
Posts: 216
Likes: 0
From: Brunswick Georgia
My Alternator went out on my 85 C4 leaving me stranded 40 miles from home, I am 71 years old so I was not too happy. My son brought me a new one, I installed it, and nothing showed up on the volt meter. I got the car home, Put it up on blocks and started chasing wires. All of the major wires from the battery to the starter looked good and have continuity. The main wire to the alternator has 12 volts when I check it with the multi-meter. Took the alternator off and too it to O Rileys, put it on the tester and it check out good. When I put it on the car, it only shows 12 volts going to the battery...
What am I missing, why is the alternator not working on the car. Need help please....
Wayne
What am I missing, why is the alternator not working on the car. Need help please....
Wayne
O Rileys bench test - volts?
battery test engine off, volts? how fast of a drop in volts?
Thread Starter
Racer
Joined: Sep 2007
Posts: 493
Likes: 0
From: Eden Utah
With key off, I have 12 Volts to the large red wire that bolts to back of alternator, and I have 12 volts to the red wire in the plug. No volts to the white wire in the plug. With key on I have 12 volts to the white wire in the plug.
Thread Starter
Racer
Joined: Sep 2007
Posts: 493
Likes: 0
From: Eden Utah
When I turn on the fans and A/C quick drop in voltage. Like there is nothing going anywhere.....
Instructor
Joined: Jun 2011
Posts: 216
Likes: 0
From: Brunswick Georgia
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Thread Starter
Racer
Joined: Sep 2007
Posts: 493
Likes: 0
From: Eden Utah
Instructor
Joined: Jun 2011
Posts: 216
Likes: 0
From: Brunswick Georgia
and did you check old alternator at store to be sure it was bad?
Thread Starter
Racer
Joined: Sep 2007
Posts: 493
Likes: 0
From: Eden Utah
Yes, the old alternator was bad, was only putting out 11 amps. If I am getting voltage at the alternator on all three connections, would that rule out a fusible link.
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
I did not add the capital letters . . . that's just like screaming DANGER . . . DANGER!!
If you run the alternator with the battery cable disconnected, the voltage may go high enough to fry some electronics, including the voltage regulator inside the alternator.
Team Owner
Joined: Sep 2003
Posts: 25,373
Likes: 2,734
"HOTROD ROY" is certainty correct in his mention of "NEVER"! This is more critical I believe of the early 12SI thru 17SI product.
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
have never seen any alt hurt by disconecting it for a sec. they run them disconected when they test them this is no different then a bench test. wayne 1 of 2 things will happen your car will die meaning the alt is not putting out anything or the car will keep running if you hae a volt meter hooked to large term of the alt while doing this if charging it will probley go up to about 15 volts/
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
I'm quoting my FSM (pg. 6D16): "NEVER operate the generator (alternator) with the output terminal disconnected."
I did not add the capital letters . . . that's just like screaming DANGER . . . DANGER!!
If you run the alternator with the battery cable disconnected, the voltage may go high enough to fry some electronics, including the voltage regulator inside the alternator.
I did not add the capital letters . . . that's just like screaming DANGER . . . DANGER!!
If you run the alternator with the battery cable disconnected, the voltage may go high enough to fry some electronics, including the voltage regulator inside the alternator.
Team Owner
Joined: Sep 2003
Posts: 25,373
Likes: 2,734
I have never looked at a service manual for alt dia. it is something I learned yrs ago. I understand the reasoning for that but for the most part it is hug wash. When they bench test a alt they test it just like I said but off the car. Your not running it forever just a sec or to to see if the alt can put out and to elimiate other things. If anyone does not like my susgetion I have no problem I understand. I do know at least 3 people in the last moth have used my way on her without ant ill effects and it help them dianoise their car
The OP's response in post #9 is indicator enough that he needs help! Not trying to be critical, sarcastic or patronizing or anything else one might want to assume but it's I believe what anyone should have passed on to the OP after the first few responses.
We all need "help" from time to time myself more frequently than others.
Last edited by WVZR-1; Jun 12, 2014 at 07:06 AM.