Headlight help needed

j0hnl34 · Mar 19, 2026

1985 K5 Blazer, when turning on brights it cuts all power to headlights three separate headlight switches and 3 separate dimmer switches on the column. Have been through the entire harness under the hood to the bulkhead, grounds are good, wiring is good. Can’t quite find anyone with my exact issue any help or input would be greatly appreciated

j0hnl34 · Mar 19, 2026

Added the brights have never worked

TomR10 · Mar 19, 2026

Got to ask the obvious, have you checked the high beam bulbs? Quad 4x6s?

ali_c20 · Mar 19, 2026

When the high beam bulbs are good check if you have power to the high beams.

Ricko1966 · Mar 19, 2026

My thoughts are you have a bad connection,you have enough connection to power 2 lights,4 overloads the circuit. A second thought though much more remote is you have a short in your high beam circuit,when you turn on the high beams it trips the breaker in the headlight switch.

j0hnl34 · Mar 19, 2026

TomR10 said:
Got to ask the obvious, have you checked the high beam bulbs? Quad 4x6s?

Yes they are functional

j0hnl34 · Mar 19, 2026

ali_c20 said:
When the high beam bulbs are good check if you have power to the high beams.When

Ricko1966 said:

My thoughts are you have a bad connection,you have enough connection to power 2 lights,4 overloads the circuit. A second thought though much more remote is you have a short in your high beam circuit,when you turn on the high beams it trips the breaker in the headlight switch.

Click to expand...

I’m leaning towards a short just not sure where else to look

j0hnl34 · Mar 19, 2026

ali_c20 said:
When the high beam bulbs are good check if you have power to the high beams.

I lose power when the high beams are on

Goldie Driver · Mar 22, 2026

Any chance the dimmer switch is out of adjustment and you are getting a "neutral" position unintentionally?

Gilmore · Mar 23, 2026

Goldie Driver said:
Any chance the dimmer switch is out of adjustment and you are getting a "neutral" position unintentionally?

I have the same problem if I go to click my high beams on I have to click it twice real fast and then I get high beams.

molus · Mar 23, 2026

If you remove the bulbs is there 12v on the high beam socket? Fairly unlikely that it’s an earth problem being the low beams work. Sometimes the socket tabs break off. Unlikely on both tho.
If there’s no 12v, work back from there. Check the terminal connection at the firewall next. Then follow back from there ect.
Someone had put a switch after the blinker relay on my truck and it took a few hours to trace it back.

goldpack · Mar 24, 2026

my 1986 has 4 headlights. I typed of them here on this thread, it has a link to the HD harness from LMC, and some pics of what 1985 era dimmer switches look like (vs. the older floor mounted button).

https://www.gmsquarebody.com/threads/faulty-light-dimmer-switch-need-help.48202/

I notice from cleaning contacts and swapping in new parts problems on one side can manifest on the other, ...just using plain old sylvania replacement sealed beams to keep it OEM.
(...which when you look at them, fit like all cars in 1985 era).

the good news: OEM type parts have been inexpensive for swapping out 40 year old stuff,
so a main switch, a dimmer switch, a $27 HD harness, can all be swapped out.

(new LED headlights seem really expensive and may just give more troubles,...vs. just adding a LED light bar at the grill, if more light is wanted).

Headlight help needed

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