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Clayso, Master Automobile Technician
Category: Chevy
Satisfied Customers: 880
Experience:  ASE Master Certified Automobile Technician. 30 Years Experience.
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Dim lights won't work everything else I replace combination

Customer Question

Dim lights won't work everything else I replace combination switch and one bulb
JA: Just to clarify, what are the exact lights you're talking about?
Customer: Headlights on 2002 zr2 s-10
JA: What is the model of your '02 Chevrolet?
Customer: 2002 zr2 s- 10
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: I replaced one bulb and combination switch,yea I'm gonna do it self
JA: Anything else you think the mechanic should know?
Customer: Not that I can thank of there is a plug 4 prong at bottom of steering column that I can't figure ou5 where plugs into
Submitted: 2 months ago.
Category: Chevy
Expert:  Clayso replied 2 months ago.

Hi There, I'm Clayso a certified master automobile technician with 30 years of automotive repair and diagnostic experience.

From your description you're either going to have a wiring issue, a problem with the underhood electrical center or the plug you mentioned under the dash. At either of the low beam headlamps ground the yellow wire with the lights on. Let me know if the low beams illuminate.

Also let me know the wire colors for the plug you mentioned and if you could send me a picture of the plug. There are a couple of circuits for the headlamps under the left side of the dash and at the steering column.

Let me know

Customer: replied 2 months ago.
OK kinda eliminated plug under dash all of a sudden the dim lights started working but then quit again.dont know where to start next.please help!
Expert:  Clayso replied 2 months ago.

Did you try grounding either of the yellow wires at the low beams to see if the low beams come on? This is a diagnostic step to eliminate one part of this circuit.

Let me know

Customer: replied 2 months ago.
OK I ground yellow. Wire and they didn't come on. What now?
Customer: replied 2 months ago.
Waiting on your reply
Expert:  Clayso replied 2 months ago.

So far it looks like the switch is grounding the relay to operate the headlamps. Let me put together a diagram so you can check for power at the under hood fuse box.

Customer: replied 2 months ago.
OK I cleaned up grounds at headlights, there's a couple plugs at bottom of fuse block that look corroded I'm trying to clean them up,waiting on diagram
Expert:  Clayso replied 2 months ago.

I'll have them to you directly. Both of the diagrams are for under the Underhood Electrical Center (UHEC)/underhood fuse block.

Are the corroded plugs you found under the UHEC?

Expert:  Clayso replied 2 months ago.

I removed all of the connections from these 2 connectors except for the circuit(s) in question. Circuit 525 is the circuit in question. The views are from the connector side so you will have to mirror the connector to locate the wires on the other side. The wire colors in question are yellow, one terminal connection will be a double yellow yellow.

Locate the double Yellow wire at pin F3 under the UHEC in the Green 32 cavity connector. Ground the double Yellow wires with the headlights turned on.

UHEC Green C4 Connector Double Yellow

If the headlights illuminate, locate and ground the Yellow wire at pin F4 in the 68 cavity Gray connector. The headlights should turn on.

UHEC Gray C1 Connector

If the head lights don't come on, verify a good clean connection at the UHEC. If these connections are good most likley the UHEC has failed internally and will have to be replaced.

Let me know what all you find

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