alternator
Thread Starter
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
alternator
1986 coupe,
My alternator wouldn't charge past 13.1 today. It was 113 degrees, and the engine was at 220 in traffic. I have seen the alternator put out more when it was just started, ( 14.4) and I believe it is temp compensated.
but today, it idled at 11.9 volts at 550 RPM, and I parked it. Came back later, it was at 160 degrees, and the charge voltage was 13.9.
Anybody have this?
I have the iceberg rear alternator casing, and I am thinking of
1. putting an aluminum section in the rear alternator support that is bolted to the exhaust manifold to keep the heat away from the alternator. Just cutting the tube, and forcing an aluminum rod into the tube, and adding screws to keep the aluminum from sliding out the tube.
or
2. maybe a micarta spacer to keep the hot support rod from actually touching the alternator case.
Or
3. both.
My alternator wouldn't charge past 13.1 today. It was 113 degrees, and the engine was at 220 in traffic. I have seen the alternator put out more when it was just started, ( 14.4) and I believe it is temp compensated.
but today, it idled at 11.9 volts at 550 RPM, and I parked it. Came back later, it was at 160 degrees, and the charge voltage was 13.9.
Anybody have this?
I have the iceberg rear alternator casing, and I am thinking of
1. putting an aluminum section in the rear alternator support that is bolted to the exhaust manifold to keep the heat away from the alternator. Just cutting the tube, and forcing an aluminum rod into the tube, and adding screws to keep the aluminum from sliding out the tube.
or
2. maybe a micarta spacer to keep the hot support rod from actually touching the alternator case.
Or
3. both.
Last edited by coupeguy2001; Jun 29, 2007 at 01:14 AM.
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
what I had done was having an alternater shop put a heavy duty voltage regulater, bigger bearing in it and he is able to make it put out on the car anything from 16 v.down, up to 160 amp in a stock small (c-124 # if I remember) case.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
First you should do something about your too low idle speed (550 rpm). No matter how hot my engine has ever been, and it has been to 220, I have never seen lower than 13.3 volts, alternator hot. At the normal 750 rpm, your waterpump will work better and your engine temp will likely stay below 220 and the alternator will have higher output voltage. If you get your idle speed up, I doubt you will have any more concerns about alternator output voltage.
Race Director
Joined: Dec 2002
Posts: 13,345
Likes: 230
From: SCMR Rat Pack'r Charter Member..Great Bend KS
1986 coupe,
My alternator wouldn't charge past 13.1 today. It was 113 degrees, and the engine was at 220 in traffic. I have seen the alternator put out more when it was just started, ( 14.4) and I believe it is temp compensated.
but today, it idled at 11.9 volts at 550 RPM, and I parked it. Came back later, it was at 160 degrees, and the charge voltage was 13.9.
My alternator wouldn't charge past 13.1 today. It was 113 degrees, and the engine was at 220 in traffic. I have seen the alternator put out more when it was just started, ( 14.4) and I believe it is temp compensated.
but today, it idled at 11.9 volts at 550 RPM, and I parked it. Came back later, it was at 160 degrees, and the charge voltage was 13.9.
I am thinking of
1. putting an aluminum section in the rear alternator support that is bolted to the exhaust manifold to keep the heat away from the alternator. Just cutting the tube, and forcing an aluminum rod into the tube, and adding screws to keep the aluminum from sliding out the tube.
or
2. maybe a micarta spacer to keep the hot support rod from actually touching the alternator case.
Or
3. both.
1. putting an aluminum section in the rear alternator support that is bolted to the exhaust manifold to keep the heat away from the alternator. Just cutting the tube, and forcing an aluminum rod into the tube, and adding screws to keep the aluminum from sliding out the tube.
or
2. maybe a micarta spacer to keep the hot support rod from actually touching the alternator case.
Or
3. both.
You might want to put in a new voltage regulator, just to ease your mind, but I don't see anything wrong with your alternator. Thirteen volts at very low rpm is normal.
In fact, I know a very good mechanic who, if the voltage regulator is the adjustable type, will set it for a maximum of 13.5VDC. He says it's easier on the battery and I see no reason to doubt him.
Larry
code5coupe
___________
Often wrong, never in doubt....
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
It sounds within range to me at that idle speed. I would check and clean your positive side connectins. BTW since I istalled the March Power and Amp pulleys I never go below 13.8 v even at hot idle.
