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High beam / low beam problem - 70 MC


jja

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I'm sure someone has encountered this before so any easy answers are appreciated. My right front (passenger) healight does not work on low beam but does turn on when I step on the high beam switch. The left side light works as it should. First thought to diagnose is to switch the lisght bulbs to verify the pass. side bulb is/is not the prob. Then clean the connections, check fuse, etc. Any other ideas?

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I get the burnt out filament reply, but wondered if the light socket is not grounded properly, why would it still work at the high beam setting? I'm going to check both.

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Would it be possible to disconnect the light from the back and run test leads from your battery to the terminals on the back of the light. Not sure which is ground but thats one way to be sure its not the wiring.

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I get the burnt out filament reply, but wondered if the light socket is not grounded properly, why would it still work at the high beam setting? I'm going to check both.

Because the high beam filiment is still intact. I had to replace one of mine when I first got my Monte. Got tired of riding around with high beams on. Try switching your bulbs from one side to the other; Or did you try that already?

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I get the burnt out filament reply, but wondered if the light socket is not grounded properly, why would it still work at the high beam setting? I'm going to check both.

 

Could be a ground issue. The high beam and low beam are different circuits. So if it is a ground issue the high beam possibly can feed back through the + of the low beam and using it as a ground to make that circuit work. Not likely unless you've had issues prior so I think your looking at a replacement. But easy way is to bench test the bulb with a battery 1 to ground lug, and + to each of the other 2. Which ever does not work is the filament that's gone, if both work then your into tracing a wiring issue. Check bulb first on bench and you know for sure if it works there it should in the car.

 

Good luck hope it's just a bulb.

 

Scott

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Thanks for all the advice. I like to troubleshoot before i run out and buy parts. Cleaned the two ground wires near the radiator support. Low beam still didn't work. Took out bulb and attached it to the plug of the other side. Still didn't come on at low beam. Concluded it must be burned out high beam filament as suggested. New one costs about $5.00. Will buy and put in and hope that is the end of it.

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Get two so they match. Halogen bulbs are a bit brighter.

True story circa 1973, had a professional auto mechanic working with me at a dealership, that was assigned to fix the front parking lights on a customers car. Said mechanic was trying to fix the problem for well over a half hour but no luck. He had test lights, volt ohm meters, wiring diagrams all over the place. I mentioned, perhaps both bulbs are just burnt out. He replied that I was just a dumb kid (1973 remember) and that was not possible. After another half hour he replaced one bulb, then the other, then drove the car out and never said a word to me about it. (Sorry, some old stories are fun to re-tell)

Bruce

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Get two so they match. Halogen bulbs are a bit brighter.

True story circa 1973, had a professional auto mechanic working with me at a dealership, that was assigned to fix the front parking lights on a customers car. Said mechanic was trying to fix the problem for well over a half hour but no luck. He had test lights, volt ohm meters, wiring diagrams all over the place. I mentioned, perhaps both bulbs are just burnt out. He replied that I was just a dumb kid (1973 remember) and that was not possible. After another half hour he replaced one bulb, then the other, then drove the car out and never said a word to me about it. (Sorry, some old stories are fun to re-tell)

Bruce

 

 

YUP KISS is was coined for a reason. Sometimes the simple solutions are the hardest to conceive for some!!!

Scott

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