Strange, brake fluid & stop lamp dash lights fading in & out

[subinewby]

So this morning just like every morning I started my 83 gl coupe reved it up a few times and let it warm up at about 300 rpms for like 5 minutes. Then when I leave and get down the road a mile or 2 it idles at about 700 just fine. Well when I first started it the brake fluid & stop lamp light came on the dash and faded off as the rpms went up. Also my volt gauge was goin up with higher rpms and down when lower mostly between 8- 18. When I first took off from home the low voltage light came on so it was below 8 but went off after it warmed up. Its never done this before. I was wondering if mabey an alternator but Im not loosing power. The brake fluid & stop lamp lights still kinda fade on when it idles after being warmed up and the volt gauge goes up and down depending on rpms. Any suggestions?

[WoodsWagon]

The alt is on it's way out, those are the classic symptoms. Replace it before it either dies and leaves you stranded, or starts overcharging and takes the battery with it.

[subinewby]

Ya thats what I was wonering.Thanks its a prety cheap n easy fix I think Ill get my suby an alternator for Christmas lol.

[987687]

Were the lights only on when it was idling really low?

The alt won't put out much when it's not running at least 700 RPMs.

Have you ever almost stalled the engine, or crawling really slow at low RPMs?

In my car all the lights come on, and the voltage gauge drops under about 400 RPMs just because the alt isn't spinning fast enough to really work.

[GeneralDisorder]

Rectifier failure in the alt. The indicator lamp circuits are on a common 12v bus and the AC current from the alt causes them to light up.

 

GD

[subinewby]

It runs fine and never has wanted to stall or any hesitation like that. Yes they only come on when the rpms are low but it just started doing this, it still runs fine. And its kinda wierd watching the volt meter move up and down with the rpms. I think Ill try a new alt and see what happens.

[987687]

My volt gauge drops down under about 1000, and fluctuates quite a bit. Sounds similar what's happening to you. I think mine either has a failing reg, or the windings are getting bad. And I have more AC in the system than I should have... so the diodes are dying... I'm keeping a lookout for a maxima alt.

[SteelyDan]

Wow, same exact thing just started happening to my hatch too. Brake fluid light and stop lamp fading in and out with the voltage gauge revving up and down. Guess I'm looking for a new alternator. Glad I checked the board today.

[Setright]

Alt rectifier...as above....just chiming in to offer my vote

[Skysm182]

Hi all, i am new here. same thing happened to me. took it to autozone to check the alternator and sure enough it was bad. replaced it, and the charge battery, stop lamp, and brake fluid lights all turned off.