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99 Electrical issue...

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Old Jul 18, 2021 | 03:57 PM
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Default 99 Electrical issue...

Car running fine with AC on...
Turn on the headlights or parking lights and AC stops and entire dash goes out.
Car still runs fine!
Anyone experience this?

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Old Jul 18, 2021 | 05:02 PM
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Originally Posted by Hammer99
Car running fine with AC on...
Turn on the headlights or parking lights and AC stops and entire dash goes out.
Car still runs fine!
Anyone experience this?
Let us know what you mean by “AC stops”. ??…blower motor stops or AC on light goes off or just blows hot air ??
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Old Jul 18, 2021 | 05:17 PM
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Blower motor and indicator light go out. Dash lights, radio, everything doesn't work. Turn the headlights off, and everything works perfectly again.

It seems like when I turn on headlights something is shorting. As if a wire is rubbed through it's insulation.?
The car has only 56K miles. Always in a temp controlled garage.

Last edited by Hammer99; Jul 18, 2021 at 05:32 PM.
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Old Jul 18, 2021 | 05:46 PM
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Originally Posted by Hammer99
Blower motor and indicator light go out. Dash lights, radio, everything doesn't work. Turn the headlights off, and everything works perfectly again.

It seems like when I turn on headlights something is shorting. As if a wire is rubbed through it's insulation.?
The car has only 56K miles. Always in a temp controlled garage.
Sounds like a GROUND problem !!...let me look at a 99 wiring schematic to see if lights, and HVAC are tied in !!
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Old Jul 18, 2021 | 06:00 PM
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Originally Posted by Hammer99
Blower motor and indicator light go out. Dash lights, radio, everything doesn't work. Turn the headlights off, and everything works perfectly again.

It seems like when I turn on headlights something is shorting. As if a wire is rubbed through it's insulation.?
The car has only 56K miles. Always in a temp controlled garage.
Turn the lights on and see if the horn works ??
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Old Jul 18, 2021 | 06:16 PM
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Yes, the horn works with the lights on.
Correction on radio not working. That works.
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Old Jul 18, 2021 | 06:28 PM
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Originally Posted by Hammer99
Yes, the horn works with the lights on.
Correction on radio not working. That works.
We just had someone today with some dim headlight bulbs…remove G101 and G102 which are behind the headlight buckets…pop the “comb” (pictured) from both grounds…clean comb with sandpaper and connector with contact cleaner and reinstall !!…try that !!



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Old Jul 18, 2021 | 06:45 PM
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You are the Man!
I will investigate tomorrow and get back.
Thank you!!
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Old Jul 18, 2021 | 06:54 PM
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Originally Posted by Hammer99
You are the Man!
I will investigate tomorrow and get back.
Thank you!!
I remember popping off that comb you had to pinch this area on both sides (arrow) to remove it !!

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Old Jul 19, 2021 | 12:20 PM
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Well that fixed it!
There was zero corrosion on either comb.
What was suspect was the contact with the ground stud...
I cleaned up the contact surfaces and that did it!

This Forum has been a wealth of knowledge.
Thank you very, very much!
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