85 K20 Scottsdale intermittent headlights

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Tomahawk4x4

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Tom
Truck Year
1985
Truck Model
K20
Engine Size
350
Hey all. Bought this pickup from an old farmer that used it to plow snow before letting it sit for 10 years. I've been fighting this for about a year now. When I got the pickup, the headlights didn't work at all. After working on a few other things, i decided to play with the headlight switch and the low beams finally came on but only the passenger side came on. Played with it some more and the drivers side came on with the passenger side but the high beams would not come on. Wiggled all the wires and it didn't help. Replaced the headlight switch and dimmer switch (on the column) and it didn't help. Few months later, high beams decided to start working. Once in a while the highs will shut off by themselves and it takes forever for them to come back and lows also work correctly when they want. I want all the advice I can get.
 

Jgonick

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West Texas
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Joel
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1985
Truck Model
K10
Engine Size
350
Start by checking the headlight grounds are making good contact.
 

Tomahawk4x4

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Tom
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1985
Truck Model
K20
Engine Size
350
Yes. Check the firewall ground on the rear passenger side of the engine too.
Those are good on the rad for sure I just repainted the top. Contacts are clean. Will check the firewall ground tomorrow I'm out of sunlight. Anything else to check for?
 

PrairieDrifter

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350, 350, 350, 350, 350, 350
Those are good on the rad for sure I just repainted the top. Contacts are clean. Will check the firewall ground tomorrow I'm out of sunlight. Anything else to check for?
You'll have to start checking continuity to ground at the headlight sockets as well as power. Just a simple cheap voltmeter will work.
 

nvrenuf

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I struggled with no headlights on my Blazer for months that turned out to be a loose male spade connector in the engine compartment side of the wiring harness bulkhead plug.

I fought this on the weekends for months and was at my wits end. I Hail Mary purchased a Power Probe and had it diagnosed in under an hour. The ability to push power through a circuit anywhere made quick work of figuring out where the dead spot was.
 

Tomahawk4x4

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Location
Iowa
First Name
Tom
Truck Year
1985
Truck Model
K20
Engine Size
350
I struggled with no headlights on my Blazer for months that turned out to be a loose male spade connector in the engine compartment side of the wiring harness bulkhead plug.

I fought this on the weekends for months and was at my wits end. I Hail Mary purchased a Power Probe and had it diagnosed in under an hour. The ability to push power through a circuit anywhere made quick work of figuring out where the dead spot was.
Interesting...
 

ali_c20

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Alexander
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Engine Size
350, 350
Welcome from Austria. Post some pics of your truck.
Methodically check all parts of the circuit one after the other so that you don't miss anything.
 

legopnuematic

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Welcome from Missouri.
 

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