Do.Man

So for about a month now, once in a while when i would drive with the headlights on and the stereo on (kenwood HU) and i press the brake pedal, the headlights would dim a tad bit and there was a couple times the HU cuts off for a bit and turn back on like when you first started the car.
This all happens when the car is warmed up already.
One time when the headlights and stereo were on and when i press the brake pedal the headlights dim really bad and the radio cut off and the car turned off.
the car starts fine and strong everytime even after the one time it turned off.

Things i've done so far is checked/cleaned all the grounds in the engine bay, cleaned/replaced the battery terminals, got a load test on the battery and it tested good,
check voltage readings: with the car off-12.8 volts, cold start up-about 14.2v, warmed up-13.5v, warmed up with headlights on-13.5v, warmed up with headlights and stereo on-13.0v and going down a bit, then with headlights,high beams, stereo, and ac- 12.9-.8 volts. Also when pressing the gas it goes back to 14.2v.

im not much of an electrical guy so i dont really know whats up. i searched and read several threads but still can't figure it out. hopefully its not the alternator..

Battery and ALT. are about a year old.

PureDrifter

iTrader: (10)

possibly could be the alternator's voltage regulator, but i'd do the big 3 grounds before i got into that.

BobN54

If your grounds check out, then I think you have one of the three diodes in your alternator going bad.

Do.Man

i was looking into that, but the thing is ,everything is stock besides the kenwood headunit and two front kenwood speakers within stock specs. would that cause that much of a drain?

thanks for replying puredrifter. if anyone can help me solve this i know you can haha

Do.Man

dammit i hope it isnt though..
is there any way to check to make sure its going bad without taking it out of the car?

PureDrifter

iTrader: (10)

it's not about draw, most reman'd alternators still have the original voltage regulators.

search around for the testing procedure but it involves checking direct alternator voltage both at idle w/o load, and at 2k rpm or something under load. if it spikes, the reg is dead. if it is consistently too low or too high, it's dead. no ssts or anything neeeded, just the test instructions and a multimeter.

Yamae

Sorry for the limited English but I think I'd better to write my experience.

Is your alternator an aftermarket one? Here in Japan, there are 2 types of alternators for the Celsior in the market. Denso's OEM alternator is very strong against heat but an aftermarket one is not strong enough compared with Denso's since it uses a different regulator which is made by some other company. Denso's has tall heat sinks but the others not as tall as Denso's

I know many Celsior owners who are having problems of low voltage. They begin to have the problem in a few years after changing the alternator due to the oil leaking problem from the power steering pump. The aftermarket alternator does not use the genuine Denso's regulator and it tends to fail in a few years. The symptom is a poor voltage regulation. But it is regulating the voltage for about 30 minutes or so after the engine is started. It begins to fail after it is heated up dropping the voltage down to 13.5V or less. Changing the regulator alone fixes the problem but you'd better to use a Denso's one. I knew a guy who has used an aftermarket one again and he had the same problem again.

fixmiester

Your symptom regarding the engine easily starting after everything dimmed when the engine died is revealing. Plus, your voltage readings during charging and loading look okay, though a little low. From that info, I suspect you have a bad connection to your master fuse block assembly, which is independent from the starter. Somewhere, you're loosing voltage under load, i.e. with A/C, lights and stereo on. Need to follow the harness from the battery into that block, and check voltage drop under load, between the positive battery terminal and several +12v locations within that fuse block, using a decent voltmeter. A reading of more than two volts shows there is a bad connection, or high resistance somewhere. A schematic would be nice, but you may not be familiar with all that, so just look for the voltage drop. Could turn out to be burned contacts in a relay, bad fuse connection, or corroded terminal connection. Sometimes those areas get hot under load, so discoloration may be visible. And yes, a good ground connection to that block is important, as well. Good luck.

Steve

steve2006

Seeing as no one has mentioned this, the car being a 1994 model and the fault appearing when the brake pedal is pressed.

The trunk wiring problem.

http://www.lexls.com/tutorials/lighting/bulbout.html

Do.Man

so i've been checking everything you guys said today, except for the trunk hinge, im doing that tomorrow.
i notice while checking the voltage level with the car running under load (with headlights on, ac, radio) the voltage stay around 13-13.5 volts and only when the brake pedal is pressed the voltage goes down to 12.8/9. And this happens even when there is only one load on for ex: just the headlights or just the ac on.
the rpms drops a bit too. like from 600 to like 550 or 500 not exactly sure.
fuses are all fine no fuses are blown or corroded.
volts never runs under 12.8 and never higher than 14.1-2. which is why i dont think the alternator or battery is bad. main grounds are also cleaned and tighten.
could a brake light ground or headunit ground cause similar symptoms?

Do.Man

also thanks for the replies everyone! i really appreciate it! if you are around the area beers on me! haha

PureDrifter

iTrader: (10)

possibly, and/or dying bulbs causing excess current draw?

steve2006

Why am I always 4000 miles away when the free beers are flowing!

Jin3198

I had the same issue with my car, it turned out to be the alty for me. I also re-wrapped the trunk harness just incase on mine, but the wiring was fine. I replaced the alty and its been fine since.

Good luck.

Do.Man

yeah im leaning more towards the alternator now as i havent found any broken wires/ shorts and grounds are all fine. changed out a couple of bulbs in the tail lights that seemed to be damaged but thats all.
gonna do a few more things before i take out the alternator and test it.
gotta see if the serpentine belt is tight enough.

oh btw did you replace the alt. with a OEM factory one or aftermarket one man?