86 GT. Basically, I start up the car without a fuss on a battery that reads 11.90v (using a multimeter) before the startup. After it starts, the battery still reads 11.90v (the console volt gauge also reads low and the warning light is on). All I have to do is give the throttle a small blip and the alternator starts charging at 14.50v. Never any major revving of the engine is needed, just a tiny blip.
This happens every time and there are no problems while driving it. There are no loud belt squeals or slips and the belt is adjusted correctly. Has this happened to anyone? Just a sign of an alternator slowly moving on to its next life?
If you turn on the headlights does it get worse? If so slipping belt.
I just tested this. The volts do dip a fair amount when I turn on the headlights, but not too much as to where the car dies. I couldn't tell by how much, since the mulitmeter leads can't stay on the battery leads by themselves and another person is needed. With the headlights on, it reads at 11.65v. Throttle blip...back to normal at 14.5v. A slipping belt does make sense, even if it doesn't make any obvious noises. I should just change the belt anyhow...
You have it correct. The diodes in the alternator are going. Assuming no belt slip, but, get the battery checked on an ammeter You could have a bad battery cell too.
All I have to do is give the throttle a small blip and the alternator starts charging at 14.50v.
I've got an '86 GT that does exactly the same thing. As long as a blip of the throttle continues to correct the issue, I'm not pulling that alternator out of there.
I have some fuzzy recollection of this problem having to do with something or another needing to be "excited". Hopefully that's the correct term. Someone here will know what the heck I'm talking about.
Make sure you get a full 12 volts to both small wires to the alt when the key is on. Low voltage will not energize the alt at low rpm. If your dash light does not work that can cause a charging problem too.
What was the fix, if I don't mind asking? I searched, but to no avail.
If the voltmeter is low or the volt light is on, I'd just give the throttle a quick blip (maybe 2000 RPM) and voltage would return to where it should be. That worked for me for about 15 years....sometimes "temporary" fixes have a way of becoming "permanent."
If the voltmeter is low or the volt light is on, I'd just give the throttle a quick blip (maybe 2000 RPM) and voltage would return to where it should be. That worked for me for about 15 years....sometimes "temporary" fixes have a way of becoming "permanent."
Ha, I read your first post as to knowing a "fix" to not having to blip the throttle. Now I see that you have just lived with the problem and blipping the throttle is your "fix"
Okay, upon further inspection of that thread, it doesn't look like an enjoyable job to find that diode within the harness. It could be on the inside of the car or inside the engine bay....or may not even exist at all.
Would swapping to an 88 alternator (and the harness adapter) just fix the issue, while giving the car a better charging system? Or would the same problem repeat itself? It's not that I don't mind digging around for diodes if I absolutely must, but if I can just swap out for a better alternator, I would go that route.
[This message has been edited by MacGyversMullet (edited 02-01-2014).]
Would swapping to an 88 alternator (and the harness adapter) just fix the issue, while giving the car a better charging system? Or would the same problem repeat itself? It's not that I don't mind digging around for diodes if I absolutely must, but if I can just swap out for a better alternator, I would go that route.
Most of us find it a helluva lot easier just to blip the throttle once.
Most of us find it a helluva lot easier just to blip the throttle once.
Haha. Yeah, I hear you loud and clear on that. Too bad it's the tiny things that get on my nerves (perfect car to own for that, I know). I'm also just thinking about resale "value" down the road if I ever to pass it along to someone else.
Has that car been converted to a 1 wire alternator? if it has it take a preset rpm to kick it in. Lots of people switch to the 1 wire to unclutter a engine bay.
Very probably your alt was 'rebuilt' and someone left out the small resistor that sits across 2 mounting screws at the regulator. That resistor is your low RPM kick-in, that would save you from having to "blip" the throttle to initiate charging.
Pete (These are some of the things you learn while working at a bench electrical shop)
[This message has been edited by thx569 (edited 02-03-2014).]
Has that car been converted to a 1 wire alternator? if it has it take a preset rpm to kick it in. Lots of people switch to the 1 wire to unclutter a engine bay.
I am not sure, but am I wrong in thinking the SI alternators are 1-wire to begin with? I was under the impression that GM's 70's and 80's SI series alternators were 1-wire, right out of the box.
Very probably your alt was 'rebuilt' and someone left out the small resistor that sits across 2 mounting screws at the regulator. That resistor is your low RPM kick-in, that would save you from having to "blip" the throttle to initiate charging.
Pete (These are some of the things you learn while working at a bench electrical shop)
That is an interesting point that I wish I knew the answer to!
So, does anyone know if converting to the CS series alternator would bypass this problem?
Hopefully that's the correct term. Someone here will know what the heck I'm talking about.
