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Low voltage on 2000 GTP headlights?

V

vertebrate

New member
What should the voltage reading be at the headlight connectors? My headlights seem absurdly dim even for our cars. I checked with my multimeter and the passenger headlight was reading about 10.2v and the driver headlight about 10v. I'm assuming these should be right around 12v, and might account for the dim headlights?

I've had the car since 2002, and maybe I'm remembering wrong, but I don't recall the headlights being this dim. They illuminate hardly anything.

Thanks,
Steve
 


Was the car running when these readings were taken? Headlights on or off?(sounds stupid but when measuring from the connector, the headlight was off unless you backprobe)

Also measure right at the battery for a comparison. I'd say as a guess, no more than .5 volts lost should be acceptable.
 
The lights were on, just with the headlight bulb disconnected. For some reason I didn't have the car running. I went back and tested again with the car on, and the voltage was up in the 12s where it would be expected. There's a minor amount of uv damage on the headlight covers, so I guess the lights really are just that bad.
 
Well when running you will be around 14.4v. 12 seems low. Is the other headlight the same? Check the grounds which are right below the headlights.
 
I just got a chance to get back out and look at it. The low beams(white wire) reads about 12.8 for both, and the high beams(green wire) reads right around 12.2. The only ground wire that I could see was coming out of the wiring tube and attaching to the crossmember above the radiator just inside of the drivers side headlight. The ground looked to be firmly attached with no visible corrosion. Are there other grounds elsewhere on there that I'm not seeing?
 
There should be one for each headlight. You'll have to do a voltage drop test, put one lead on the low beam wire and the other on the positive battery post. Shouldn't be over .5v really. Same on the negative, one lead on the ground for the bulb, other on the negative cable at the battery. If you're really getting 2 volts less at the connector than system voltage, this test will tell you where the drop is.
 


I tried leaving the headlights connected while doing it and back-probing the connectors using pins inserted into the connector. The positive side of both headlight was about 3v(maybe due to some resistance from the pins I was using). The negative side was like 5mv. I tried testing voltage drop at the 60a fuse in the box, and got something in the <10mv range. Am I correct that there are no connections between the underhood fuse box and the lights?

I'm pretty new to electrical troubleshooting, but assuming I did this all correctly does this imply that something is wrong with the wires coming from the fuse box to the lights? Would it be safe(or serve any purpose) to try and jump from the positive battery terminal to the low beam connection and confirm that that does what's expected?
 
You could jump the low beam wire to positive, and if you see them get much brighter then you will have a visual on what they're supposed to look like.

There is another connection to the headlights, the DRL resistor. It's supposed to be bypassed when you choose headlights and drops the voltage 2 or 3 volts. This may be your problem, but they go through the high beam I believe, so I'm not sure it could ever effect the low beams. It depends on how it's wired.
 
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