Dimming headlights and interior lights?

91ma70 · 05-26-2010, 04:01 AM

Okay one more thing, i have a problem where the headlights and guage illumination will dim significantly when i hold the brake. the volt meter dipps to around 11-12v when this happens, normally its around 14v. I suspect that its the alternator or could it be the battery or something else? temporarily i rev to 2k rpm @ idle sometimes and let the lights comeback to full strenght. Any Advice?

Green7mgte · 05-26-2010, 06:24 PM

sounds like the alternator. go to autozone and have them test it.. it's free. report back once thats done. if the A.Z person gave your alternator the all clear we can go over some more possibility's.

91ma70 · 05-27-2010, 02:59 AM

yeah, thats what i was going to do. hopefully thats the problem since i have a new alt sitting in my garage somewhere.

bryanf89 · 05-28-2010, 12:49 PM

dude i had the same problem except i had a new alternator...i thought i had a short circuit since the battery would end up dead sometimes...it ended up being the pulley...i had to put a tiny pulley because according to gear ratio, the smaller the pulley the more revolutions its makes with one spin of the crankshaft...that pulley cured the problem

btwilson86 · 05-28-2010, 06:01 PM

Changing the pulley could make it work for awhile, but that's nothing more than a band-aid. Spinning the alternator faster to compensate for an improperly working part will just put more stress on other parts of it, such as the bearings, causing it to fail early.

bryanf89, I suspect your new alternator was defective from the start (every manufacture has a certain percentage of defective parts).

I would suggest that both of you take your alternators (with the factory pulleys) to an auto parts store near you and get them tested. Also check the wiring coming from your alternator to make sure it's not old and brittle, as this can cause poor charging. If you have a voltmeter, you can check the voltage at the positive lug on the alternator and a chassis ground. With the engine running, you should have around 13.5 volts. Now check the voltage at the battery (still with the engine running). If the voltage deviates at all, you need to inspect/replace your wiring.

Let us know what you find

91ma70 · 07-06-2010, 06:10 AM

So i change the alternator, seems to work fine now!

Green7mgte · 07-06-2010, 03:42 PM

glad that worked out!

91ma70 · 07-10-2010, 05:14 AM

haha the same thing happened a few days ago! turnout to be the battery this time. Anyway replaced it and so far so good..

Homicidal Hippie · 12-31-2010, 02:37 AM

I had a problem with my alternator. Went to Schucks and had it tested. failed both times. so i bought a new one, but the headlights still dim when i press on the brake. the new alternator puts out about 13v. my battery is about a year and a half old. just checked up on it. put some more water in the holes. my alternator belt pully is a little squeeky. I dont know whats wrong with it. i know almost nothing about cars. I've had my dad and my boyfriend both look at it but they've never worked on a supra before so they dont know what to do either.

Green7mgte · 12-31-2010, 07:11 PM

Quote:

Originally Posted by Homicidal Hippie

I've had my dad and my boyfriend both look at it

glad to see in this day and age people aren't afraid to show who they are..

so new alternator? good battery? your belts are a tad squeaky, best replace those.

05-26-2010, 04:01 AM	#1
91ma70 3" Exhaust Join Date: Feb 2010 Location: Irvine/Lancaster CA Posts: 61	Dimming headlights and interior lights? Okay one more thing, i have a problem where the headlights and guage illumination will dim significantly when i hold the brake. the volt meter dipps to around 11-12v when this happens, normally its around 14v. I suspect that its the alternator or could it be the battery or something else? temporarily i rev to 2k rpm @ idle sometimes and let the lights comeback to full strenght. Any Advice?

05-26-2010, 06:24 PM	#2
Green7mgte Supra Forum Moderator Join Date: Nov 2009 Location: Green-Ohio Posts: 1,297	sounds like the alternator. go to autozone and have them test it.. it's free. report back once thats done. if the A.Z person gave your alternator the all clear we can go over some more possibility's. __________________ 92 Ma71 7mGTE Auto. SafcII Supra FAQ Supra MKIII FAQ Classified Section guidelines :

05-28-2010, 06:01 PM	#5
btwilson86 Super Moderator Join Date: May 2007 Location: Billings, Montana Posts: 1,034	Changing the pulley could make it work for awhile, but that's nothing more than a band-aid. Spinning the alternator faster to compensate for an improperly working part will just put more stress on other parts of it, such as the bearings, causing it to fail early. bryanf89, I suspect your new alternator was defective from the start (every manufacture has a certain percentage of defective parts). I would suggest that both of you take your alternators (with the factory pulleys) to an auto parts store near you and get them tested. Also check the wiring coming from your alternator to make sure it's not old and brittle, as this can cause poor charging. If you have a voltmeter, you can check the voltage at the positive lug on the alternator and a chassis ground. With the engine running, you should have around 13.5 volts. Now check the voltage at the battery (still with the engine running). If the voltage deviates at all, you need to inspect/replace your wiring. Let us know what you find __________________ 1989 7MGTE R154 Targa Top White Package w/Blue Interior Driftmotion 57trim CT26, Upgraded Intercooler, 2.25" Hard Pipes, 3" Turbo Back Exhaust with Test Pipe, HKS VPC w/GM 3 bar MAP sensor, APEXi S-AFC, Walbro 255lph fuel pump, ProSport EVO Series Boost / Fuel Pressure / AFR gauges, Lotek a Pillar Gauge Pod, HKS Type 0 Turbo Timer, Eibach Lowering Springs, Tokico Illumina II TEMS struts, custom powder coated Motegi Racing TrakLite wheels

07-06-2010, 03:42 PM	#7
Green7mgte Supra Forum Moderator Join Date: Nov 2009 Location: Green-Ohio Posts: 1,297	glad that worked out! __________________ 92 Ma71 7mGTE Auto. SafcII Supra FAQ Supra MKIII FAQ Classified Section guidelines :

05-27-2010, 02:59 AM	#3
91ma70 3" Exhaust Join Date: Feb 2010 Location: Irvine/Lancaster CA Posts: 61	yeah, thats what i was going to do. hopefully thats the problem since i have a new alt sitting in my garage somewhere.

05-28-2010, 12:49 PM	#4
bryanf89 3" Exhaust Join Date: Nov 2009 Location: NYC Posts: 231	dude i had the same problem except i had a new alternator...i thought i had a short circuit since the battery would end up dead sometimes...it ended up being the pulley...i had to put a tiny pulley because according to gear ratio, the smaller the pulley the more revolutions its makes with one spin of the crankshaft...that pulley cured the problem

07-06-2010, 06:10 AM	#6
91ma70 3" Exhaust Join Date: Feb 2010 Location: Irvine/Lancaster CA Posts: 61	So i change the alternator, seems to work fine now!

07-10-2010, 05:14 AM	#8
91ma70 3" Exhaust Join Date: Feb 2010 Location: Irvine/Lancaster CA Posts: 61	haha the same thing happened a few days ago! turnout to be the battery this time. Anyway replaced it and so far so good..

12-31-2010, 02:37 AM	#9
Homicidal Hippie Stock Join Date: Dec 2010 Location: Washington Posts: 1	I had a problem with my alternator. Went to Schucks and had it tested. failed both times. so i bought a new one, but the headlights still dim when i press on the brake. the new alternator puts out about 13v. my battery is about a year and a half old. just checked up on it. put some more water in the holes. my alternator belt pully is a little squeeky. I dont know whats wrong with it. i know almost nothing about cars. I've had my dad and my boyfriend both look at it but they've never worked on a supra before so they dont know what to do either.