drivers headlight failure

turbomatt · Feb 17, 2020

Howdy knowledgeable masses.. hows this for puzzling.. lights on my 79 suburban were replaced recently with high output jobs.. maybe 5 hours of nighttime driving on them. Driving home other eve and noticed drivers side out high and low beam. Trusty voltmeter shows just under 11v on both sides with engine off so I buy a new light. Plug it in. ..almost immediately the low beam pops, switch it to high beam and within 20 seconds, the high beam fails... this is with the engine off and showing 11v on the meter... never seen where <12v would make a filament fail , let alone both within a few seconds.. harness runs from pass side which is fine and ground seems fine... any ideas?

Snoots · Feb 17, 2020

You should have battery voltage there.
However, the older models have the bulb voltage going thru the switch. Since you went to high output bulbs without changing to a relay direct setup you're likely getting the bulb to act as a fuse because of the required load that your present wiring cannot handle.
Check ALL of your grounds first. Make certain that all of you connections on that circuit have no corrosion.
When you have your battery voltage at the bulb connectors WITHOUT THE BULBS PLUGGED IN you should be good to go.
This is only a temp fix.
Check with @chengny for an upgrade kit.

Matt69olds · Feb 17, 2020

If you have one of the old bulbs, plug it in. Turn on the lights, take the positive probe of your voltmeter to the green or tan wire (depending on if your high or low beams are on) and the negative probe to the POSITIVE post of the battery. Whatever the meter reads is the amount of voltage lost in the wiring. Ideally, you shouldn’t see more than a couple tenths of volt. I’m guessing your going to see much more than that, since your showing 11 volts with the bulb unplugged. Check the connections at the dimmer switch, check for corrosion at the headlight sockets. The best bulbs in the world will be useless without proper voltage/current to run them.

AuroraGirl · Feb 18, 2020

Also good to know what his battery is at when truck is off with the power at the wiring, so we dont have a case of a battery thats too... strong? or weak, kind of thing. Funky what a battery can do

turbomatt · Feb 18, 2020

Thanks for the responses...if the headlight was serving as a fuse, wouldn't the first headlight in the harness burn first... secondly..with diminished voltage shouldn't I just be getting low lumen output from the light, not it popping? I know I have voltage drop as the factory harness is pathetic but I have never had an issue other than a dim light unless the alternator was spun at high rpm

ali_c20 · Feb 18, 2020

Have you thought about a heavy duty head light harness with relais ? No more dim lights and only low load on the headlight switch.

Matt69olds · Feb 18, 2020

You can check for voltage drop on the ground side by following my instructions, just put the negative meter probe on the ground terminal of the headlight, and the positive on the negative post of the battery.

Electrical things can do all kinds of weird crap. Start with fixing what you know is wrong, get the wiring sorted out first. Who knows, maybe the lights get too hot with lower voltage? I agree, most electrical things burn up from too much voltage.

gmachinz · Feb 18, 2020

Are these stock type replacement H6024s or H4s?

F-64 · Feb 18, 2020

What is the brand and model number on this light that keeps blowing?

F-64 · Feb 18, 2020

Those lights could have also been cracked which would have allowed the filaments to burn up.

Snoots · Feb 19, 2020

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Reinovator · Mar 1, 2020

A good idea when up grading Is to run a relay using battery voltage for the power to the headlamps and your switch as the power for the relay saves on switch life and Bulb life I used one for high and one for low beam,( not necessary unless your powering both elements at the same time which is another can o worms which I will not get in to) and as stated in other posts always check your grounds, and connections. mine are brighter I have used this on my 86 motornome( GM chassis) and my 77 gmc panel truck just my thoughts.

drivers headlight failure

turbomatt

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