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Discussion Starter · #1 ·
alright, I understand people come on here and make posts, asking for something and it turns out to be simple, well, i got a beautiful mystery for the supra guru's could be something simple, or not....and ill explain what happened and what my thoughts are...

We have a massive cruise night here, every "nice" sunday, so I head out right, and im cruising for about 2 hours now, and I start to notice when i put on my brakes, my headlights start to dim....within the next minute or 2, they start to totally go out when i put on the brakes.....im like "wtf?" so i start to really pay attention....within another minute when i put on the brakes the whole electrical starts to die, my cd, starts skipping, then within another minute it would kill the whole system, my e-brake light, trac control everything would reboot and start again, but ONLY when i first put on the brakes. I push the brake in, everything dies and comes back on, and then its perfectly fine even with my foot still on the brake coming to a stop....and ONLY when id use the brake...

So i pull over and talk to a buddy of mine on the phone, now i cant really do diagnostics on the car DOWNTOWN or anything, so i gimp it too a parking lot, turn it off and wait about 5 mins checking the connections i can, etc....everythings fine...Turn it back on, and proceed to drive it towards the highway where i can scoot home without any redlights so i dont have to brake.....from then on, its perfectly fine....nothing wrong i tap my brakes repeatedly, etc....Nothing happens, its totally fine, all the way home, nothing its still perfectly fine...

My thoughts are....

1)It cant be my alternator...because it would have "typically" slowly started dying on me, and it wouldnt have been perfectly fine all the way home....

2)It's not my serpentine, because then everything would have died, period....not "only" when my brakes were used.

3) I think its my aftermarket immobilizer installed last month....possibly a shotty job, and it started grounding out on me and started killing power....or my brake was pulling the wire and the chip back so it was loosing the signal?

I dunno, any ideas? and no i havent washed the engine or anything.
 

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Turn on the car at night, turn on all electrical (interior lights, headlights, radio, door lights, hazards), and notice if the lights dim or not when accelerating/idle, if the electrical dims and come back, its your alternator. Leave the car in park or neutral.
 

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Discussion Starter · #4 · (Edited)
supraswap said:
take alternator out and have it tested.
only way to make sure and rule it out.

good call, i was actually planning to take it in tommorrow and have her tested out.

get the belts checked also while im there.

Incase u cant read my sig or anything. I have a 94-TT-6-speed. Only intake and exhaust... and only 60,000 km's on her...
 

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Discussion Starter · #5 ·
ShinRyu said:
Turn on the car at night, turn on all electrical (interior lights, headlights, radio, door lights, hazards), and notice if the lights dim or not when accelerating/idle, if the electrical dims and come back, its your alternator. Leave the car in park or neutral.

Went outside just now and tried that out, everything is perfectly strong, no dimming whatsoever at all....

Turned on stereo, both interior lights, headlights+fogs.... etc....

I'm gonna take it for a little boot around the area, and see if she acts up.... if not im gonna pull my under-dash out on the drivers side and see if my gps harness and immobilizer are mingling together or the immobilizer chips moving around, etc...
 

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Check by your brake pedal to see if there are any wires around there. You could possibly be pulling some wires, causing a short.
 

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It is when you put on the brakes? Simple, remove your battery cables, clean terminals and connectors, seat fully, tighten the piss out of them

I had this happen to me also... your battery cables have a shotty connection.
 

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^^^I agree with the above, but you also cannot rule out the battery/alternator combo. When mine went, the symptoms were pretty similar (a bunch of my dash lights would come on and off together as well) but I assumed since it didnt happen all the time it couldnt be the alternator, but it was and hasnt done it since I replaced it. When the symptoms are happening, you can pull over and test the charge on the alternator, mine wasnt charging enough when it was happening so I knew it was the alt.
 

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Go to a battery shop. We have a tester that can hookup to your car and it will tell you if your alt is bad and will also test your battery. Most shops should have a newer load tester like this.

If you can't get to a shop quickly just get yourself a voltmeter and jump the battery posts and read the voltages at idle under no load and then turn on all loads and retest. If your alt is good you'll get a reading of 13 or more under load. Your voltages should not drop between tests down more than 1v or your regulator is most likely going bad in the alt. If your reading is low hold the rpm at 2k and retest to see if the measurment changes again with a no load then load test.


Mike
 

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Discussion Starter · #11 ·
mike91t said:
Go to a battery shop. We have a tester that can hookup to your car and it will tell you if your alt is bad and will also test your battery. Most shops should have a newer load tester like this.

If you can't get to a shop quickly just get yourself a voltmeter and jump the battery posts and read the voltages at idle under no load and then turn on all loads and retest. If your alt is good you'll get a reading of 13 or more under load. Your voltages should not drop between tests down more than 1v or your regulator is most likely going bad in the alt. If your reading is low hold the rpm at 2k and retest to see if the measurment changes again with a no load then load test.


Mike

I'll get on that tommorrow, let ya know the results. What am I lookin at for a new alternator? should I get an aftermarket one? or does it really matter?
 

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I remember it was at least a couple hundred for the alt., it was a factory rebuilt with a one year 12k mile warranty on it. Are you running anything extreme as far as sound system or electrical goes?
 

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I went to a local auto electrial shop and had mine rebuilt for $120. It charges now at 14+ even with electric fans.

Mike
 

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I'd bet the regulator in the alternator is crapping out
 

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I too think it is the alternator. When you get it tested remember; just because a piece of test equipment says it's OK, it doesn't necessarily mean it's really OK.

I have had two that tested fine at the parts store, but were not fine when on the car in a real world driving environment.
 

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Discussion Starter · #16 ·
so pretty much I may as well just replace the damn thing hahaha, it is afterall a 12year old car, and although it only has 60,000Km's on her...well.....I'll have to change it one day anyway correct?
 

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There's plenty of tests you can do at home w/o taking it to a shop. But you'll need a voltmeter to do them.

From what I'm hearing, the lights are dimming when the brake pedal is initiall pushed, then it started running rough and eventually died when the brake was initially pushed on. But you were able to start the car after that? If the alternator wasn't working, the battery shouldn't have been enough to start the car right up.

I'm thinking it's less likely the alternator. First thing to do is check the voltage across the battery while the car isn't on. Then, turn on things like headlights, stereo, etc. and see if the voltage drops a lot. Then, press the brakes on and off. Check to see if the battery voltage drops when the lights dim or not. Now start the car and perform the same test. Battery voltage with the car running should be at least mid 13V.

Results:
If the battery voltage is stable during all this, and the car cranks fine, and the voltage while running stays above 13V....the alternator isn't likely the problem.

If the battery voltage does dip a LOT when the brakes are first applied, or if the engine cranks slowly, or the battery voltage is below 13V while running, the alternator *is* the likely problem.

Next test - Assuming the alternator tests okay, there's a good chance that there's corrosion in an electrical connection for the power feeding the car. The starter gets a line straight from the battery. But the rest of the electrical goes through a large fuse (drivers side of engine bay for us US folk). Perform the same test as above, but put the positive lead of the voltmeter on the output of the fuse (keep the neg on the battery). This will test for voltage drops across the large fuse.

Next test - checking if there's a ground problem between the engine and chassis. Make sure chassis is well grounded to the battery.

Next test - how about the light malfunction system? It's a little box hidded in the drivers side rear 1/4 pannel (near the fuel pump controller). Broken solder contacts on that box are pretty common. Could be causing things to go haywire???

Let us know what results you find out.
 

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Next test - how about the light malfunction system? It's a little box hidded in the drivers side rear 1/4 pannel (near the fuel pump controller). Broken solder contacts on that box are pretty common. Could be causing things to go haywire???

Let us know what results you find out.

Bringing up an old thread here...but what is the light malfunction system? Is this "box" in the repair manual anywhere?
 
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