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07-19-2019, 05:12 PM | #1 |
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Join Date: Apr 2018
Location: San Francisco, California
Posts: 52
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High beams work, headlights don’t.
Hey all
The high beam switch on the floor works. Headlight switch doesn’t work. I have swapped out all headlights and I know they work. Is there a relay? The headlight pull set is a bit rough. What the normal cause of this? |
07-20-2019, 03:46 PM | #2 |
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Join Date: May 2012
Location: Assaria, Ks
Posts: 465
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Re: High beams work, headlights don’t.
What year truck? If the dimmer switch is on the floor, that could be the culprit. Could be the switch, or just a bad connection in the plug in. That's my opinion, but it's not worth much! good luck
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07-20-2019, 10:25 PM | #3 |
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Join Date: Dec 2017
Location: Elkhart, Texas
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Re: High beams work, headlights don’t.
We need more information to give detailed trouble shooting procedures. Be that as it may, here is a basic headlight circuit description.. Most models don't have factory installed headlight relays.. Fuses aren't used either... The headlight switch has a built-in circuit breaker.. Over the years, the breaker weakens, and trips for no reason and the only repair is switch replacement..
Power is fed to the switch, one wire goes from the switch to the dimmer switch common terminal.. Power leaves the dimmer switch through 2 wires.. Depending on the beams (hi or lo) selected by the dimmer switch, power is routed to the headlight bulbs. The two wires from the dimmer switch split near the back of the radiator support and go to each headlight. Using a volt meter or test light, start at the headlight switch and follow the power path through the connections, checking for loose and or bad connections including grounds.. If you have power to the headlight switch but nothing coming out, check the plug connections first.. It's not uncommon for loose connections to develop, causing heat to develop on these connections causing plug failure. If all is well at the plug, the switch is probably bad.. |
07-21-2019, 07:25 PM | #4 |
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Location: Somewhere
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Re: High beams work, headlights don’t.
Cycle the dimmer switch about 10 times.
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07-21-2019, 08:06 PM | #5 | |
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Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,977
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Re: High beams work, headlights don’t.
Quote:
I can only assume the HI beams light but the Low beams do not... That is probably incorrect but my crystal ball is on the fritz. The headlamps have a fusible link in the feedline not a fuse... usually at the starter BAT terminal. It can differ by model year. There's no mention of the model year or other pertinent information. Again I find my crystal ball insufficient to the task. I can't recall a circuit breaker in the headlamp switch itself. If the parking lamps light up there is power to the switch. The dimmer is a single pole double throw switch. It has three connections. Power in from the headlamp switch, Low beam out, and HI beam out. If the HI beams light and the Low beams do not, as his verbiage seems to imply, then the dimmer or the dimmer plug is suspect.
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1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...
And please let us know if and how your repairs were successful. |
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07-21-2019, 10:28 PM | #6 |
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Join Date: Apr 2018
Location: San Francisco, California
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Re: High beams work, headlights don’t.
Hey all
Sorry for the vague initial post and no follow up. It’s 76 C10 stepside, Scottsdale trim with a 350 engine. New wiring harness installed and the high beams and low beams worked but Suddenly the low beams, as in when I pull the light switch on the dash the low beams don’t come on - park lights do come on though. When I step on the switch on the floor the high beams do come on. I replaced the headlights and the same still happens I’ve ordered a new floor dimmer switch and a new dash switch |
07-21-2019, 10:30 PM | #7 |
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Join Date: Oct 2008
Location: Wentworth, NH
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Re: High beams work, headlights don’t.
It's the dimmer or the dimmer plug.
You can take the headlamp switch back.
__________________
1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...
And please let us know if and how your repairs were successful. |
07-22-2019, 10:07 AM | #8 |
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Join Date: Dec 2014
Location: Euless, Texas
Posts: 519
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Re: High beams work, headlights don’t.
I had a similar situation happen a few weeks ago. Pulled headlight switch, no lights. Pressed dimmer switch, lights came on high and would cycle low to high with each press. Replaced dimmer switch, solved.
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1974 Cheyenne 10 LWB Stock 350 W/HEI /TH350/AC/4 BBL Quadrajet Mopar by Birth Chevy by Choice |
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