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Driver-side Low beam Not Working (electrical issue not bulb) PLEASE HELP

TxHummer07

Well-Known Member
Messages
55
Location
San Antonio
My problem:
2007 Hummer H3 Base

The other week, my driver side headlamp just went out. Thought nothing of it, and got around to replacing it today.

So I switched with new bulbs, nothing. The high beam continues to work on both sides...I pulled the Driverside headlamp fuse and then both left and right beams lit up but very dim. I put the fuse back in and Driverside lamp goes off immediately and the passenger front low beam goes back to normal, nice and bright. Then I hit the high beams and the high beams work perfectly.

Any ideas are welcome, my immediate thought was ground issue, but where would I start?
 

4speedfunk

Well-Known Member
Messages
4,212
Location
Tardville
Disconnect the battery.
Pull the entire fuse block out.
Remove and check the two large connectors underneath for bent prongs or corrosion. Reseat the two connectors to the bottom of the fuse block and reconnect the battery.

Those two connectors are very difficult to work with....the latches are troublesome and it's easy to bend the prongs during installation. You must get the two plugs latched & locked before putting the fuse base back in place.. A bent prong can effect a circuit without blowing a fuse.
 

Happy Hummer

Well-Known Member
Messages
1,302
Location
Wisconsin
Im going to suggest to inspect and clean your ground at each point for the lights and at the frame. Also are you running the oem battery cables?Chris
 

RadioMike

Active Member
Messages
34
Location
Abbeville, SC
Relay #70 under the hood switches the ground from the High Beams to the low beams. If High beams are fine, the ground to frame is fine. It sounds like you have a dirty contact on this relay. Just as a test, take relay 70 out and bump hard a couple of times and put back in and see if the lights work? This relay sounds like what needs to be replaced.
 

TxHummer07

Well-Known Member
Messages
55
Location
San Antonio
Im going to suggest to inspect and clean your ground at each point for the lights and at the frame. Also are you running the oem battery cables?Chris

Any insight to where the grounds are for the lights? Before i start removing things that I dont need to take apart haha..thank you!
 

TxHummer07

Well-Known Member
Messages
55
Location
San Antonio
Relay #70 under the hood switches the ground from the High Beams to the low beams. If High beams are fine, the ground to frame is fine. It sounds like you have a dirty contact on this relay. Just as a test, take relay 70 out and bump hard a couple of times and put back in and see if the lights work? This relay sounds like what needs to be replaced.

I actually tried this, i have a few extra relays and i too the original out and bumped it and the passenger front still lights up but the driverside doesnt still
 

RadioMike

Active Member
Messages
34
Location
Abbeville, SC
OK, relay 75 is the Headlamp B+ relay. When the lights are called for, this relay cuts on and supplies 12 volts to both right and left headlamps. High and low beam. The right side headlamp goes through the #40 fuse 10 amp. High and low beam. The left side headlamp goes through the #41 fuse, 10 amp. High and low beam. So when the headlights are on, you have 12 volts B+ going to the common of the high and low beam filiment of both headlights. This is the orange wire to each headlight. There is a dark blue and a pink wire from each headlight. They go to the relay #70 which either puts the pink or dark blue to ground for high or low beams. The headlights don't just ground to the chassis. They go through relay 70. Hope this helps.
 
Last edited:

RadioMike

Active Member
Messages
34
Location
Abbeville, SC
It almost looks like and issue with the new bulb or the bulb socket on the drivers side.
Take a volt meter at the drivers side bulb socket and make sure you have 12 volts to ground on the orange wire both on low and high. Next you can test from orange to blue and orange to pink. One pair should be 12 volts on high and the other pair 12 volts on low beams.
 

TxHummer07

Well-Known Member
Messages
55
Location
San Antonio
It almost looks like and issue with the new bulb or the bulb socket on the drivers side.
Take a volt meter at the drivers side bulb socket and make sure you have 12 volts to ground on the orange wire both on low and high. Next you can test from orange to blue and orange to pink. One pair should be 12 volts on high and the other pair 12 volts on low beams.

Thank you!! I will definitely check this out when I have some time to mess around with it!! I actually tried 3 different lights, the original ones, the new ones and an extra set I have for backups in the trunk storage area(forgot i had them while putting tools away) Thank you again, hopefully it works!!
 

TxHummer07

Well-Known Member
Messages
55
Location
San Antonio
So I finally had a day off to get into it and I was on another forum and someone had the same issue, he recommended using electrical cleaner on a the connections and had a can of compressed air and clean out the connectors, and *knock on wood* its working like nothing ever happened....Both lows work and both high's work. Now with that being said I ran my HID's (low/hi kit) with the seperate relays and direct power access from the battery (done the correct way) and its working like a champ

Then I decided to mess around with the skidplate some more...stripped, polished and painted the rest and wrapped it with PPF















 
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