"No Charge" Light Half Lit

Lord Fleetwood · #1 (**permalink**) 09-04-09, 06:38 PM

On my 1986 Fleetwood Brougham the "No Charge" light is dimly lit when it is supposed to be off. When I put the key in the ignition and turn to the accessory position, it will come on bright like it is supposed to do to tell me it is working. When it should go off, however, it just goes to being dimly lit and stays that way until the car is turned off.

The car is not overheating at all, so it is not actually anything wrong with the cooling system (especially since it will be half on even when the engine is cold).

I did have a similar problem happen on my 1995 Fleetwood Brougham with the temp light. I had a shop replace the temperature sensor, and when I got it back the temperature light did the same exact thing as this charge light is doing. When I brought it back to them they found the problem and told me that when one of the guys changed the sensor, he did not put the wire harness on correctly/fully and it was causing some voltage to get to the light. It would seem that this light is on for the same reason, that is, a harness or ground is not correctly on and is allowing voltage to get to the light. I tried tracing the wires from the battery and alternator but could find no obvious sensor or missing ground. All the wires from the battery and alternator went in a sheath and ended up in a big wire plug by the firewall.

Anybody have any clue what might be causing this and where I could/should look to find the problem?

Angry Matt · #2 (**permalink**) 09-04-09, 08:15 PM

The "no charge" light is referring to the alternator not charging or the battery being at low voltage. Does it ever change brightness? Mine comes on, but when I rev the engine (spinning the alternator faster) it goes out. I would search for a problem in the charging system, not the cooling. How's the alternator output?

Lord Fleetwood · #3 (**permalink**) 09-04-09, 08:35 PM

Oops...I'm a complete idiot. In that second paragraph I meant that there was no problem with the charging system, not the cooling system. For some reason I was interchanging this problem with the one I mentioned on my '95, which I mentioned in the next paragraph. I put there was no problem with the cooling system when I meant there was no problem with the charging system.

I have checked the alternator and and battery with a multimeter and they seem fine. I have had no charging problems. The light does not change brightness with revving and I have had this problem for a few weeks so if it were the charging system I think I would have had something happen by now (like needing a jump). The light is only dimly on, to the point where you can't see it well on a sunny day. Since I have no apparent charging problem, I figured it is a problem with the light itself, not the system it is monitoring.

ewill3rd · #4 (**permalink**) 09-04-09, 09:04 PM

If this is an old school (and I am sure it is) alternator it has a 3 diode bridge inside.
One of the diodes could be shorted internally causing a path to ground for the light.

It would be hard to spot without something like an oscilloscope but I'd guess that 2/3 of your alternator is working fine and the other 1/3 is not.

There are some tests you could run but it has been so long since I have had to do that I couldn't even think of where to tell you to start.
If I were to load the parts shotgun I'd put an alternator on it.
A VAT-40 tester should be able to identify a failed diode.
Most shops have one on hand.

Angry Matt · #5 (**permalink**) 09-04-09, 11:32 PM

Any chance there's another light on in the dash, like the check engine or something? I've had an instance where my check engine light was on and the light from that bulb was making it look like other things were slightly lit.

sven914 · #6 (**permalink**) 09-04-09, 11:37 PM

According to my OEM factory service manual, if the no charge indicator lamp is lit dimly with the engine running, then it is a bad diode.

I recommend that if your going to be performing your own repairs, that you purchase a factory service manual. There are a few on eBay for your 86.

flux1414 · #7 (**permalink**) 09-05-09, 12:59 AM

I love this place, I have had the exact same condition for about a week solid and two weeks before that intermitently. Figured I would just replace the alternator but now I don't feel like I'm tossing parts at. Thanks!

Any opinions on remanufactured alternators? Damn near every alternator I find in parts stores (autozone, rockauto) are remans, are they worth it?

Lord Fleetwood · #8 (**permalink**) 09-05-09, 02:59 AM

There are no other check lights on, so it is not light bleeding over from another check light.

The diode problem sounds like a good possibility, though I do not have the means to check it so I might have to just get another alternator and try it. As always, thanks to those who replied!

Lord Fleetwood · #9 (**permalink**) 09-05-09, 03:07 AM

Quote:

Originally Posted by sven914

According to my OEM factory service manual, if the no charge indicator lamp is lit dimly with the engine running, then it is a bad diode.

I recommend that if your going to be performing your own repairs, that you purchase a factory service manual. There are a few on eBay for your 86.

Yeah, I should get a factory service manual. I guess I haven't because my friend bought one for his 1990 Fleetwood and it cost over $150. Though I am not against spending that much money for the wealth of knowledge they contain, the amount has always made me procrastinate on the issue. Thank you for this link since it shows me I can get one and not spend a bunch. I didn't realize there were so many cheap ones on eBay.

ewill3rd · #10 (**permalink**) 09-05-09, 10:33 AM

There are other things it COULD BE but that sounds like the most likely cause based on the information we have here before us.

It is kind of rare but I have seen it before.

Slacker · #11 (**permalink**) 09-05-09, 12:19 PM

I've also had this issue when the clip connector to the back of the alternator had a broken wire.

caddeville89 · #12 (**permalink**) 09-05-09, 11:04 PM

Quote:

Originally Posted by Lord Fleetwood

Yeah, I should get a factory service manual. I guess I haven't because my friend bought one for his 1990 Fleetwood and it cost over $150. Though I am not against spending that much money for the wealth of knowledge they contain, the amount has always made me procrastinate on the issue. Thank you for this link since it shows me I can get one and not spend a bunch. I didn't realize there were so many cheap ones on eBay.

I bought a dealer service manual for my '90FWB for $20 on E-bay. Just keep your eyes open.

Lord Fleetwood · #13 (**permalink**) 09-06-09, 05:16 PM

I popped a new alternator on and the light is now gone. It would seem the diode was the problem as mentioned and the new alternator was the remedy. I appreciate everyone's help.

ewill3rd · #14 (**permalink**) 09-07-09, 12:16 PM

Thanks for posting your fix.