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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: street37 on September 16, 2018, 04:01:00 PM

Title: Only head lights are working!.
Post by: street37 on September 16, 2018, 04:01:00 PM

I do not have any interior and reverse lights, my parking and tail lights only work when I have the head lights on high beam. Also when I have the head lights on high beam my interior light under the dash comes on. I have replaced all fuses, circuit breakers and head light switch with no luck. Any ideas would be great.

Title: Re: Only head lights are working!.
Post by: street37 on September 16, 2018, 04:02:47 PM

I forgot my truck is a 1985 C10.

Title: Re: Only head lights are working!.
Post by: Rapid Roy on September 16, 2018, 04:37:03 PM

Welcome

Title: Re: Only head lights are working!.
Post by: JohnnyPopper on September 17, 2018, 02:01:10 PM

Look for wiring that has been cut and patched back the wrong way. Look for colored wiring that changes color at the splice point. Try to restore to original state.

Title: Re: Only head lights are working!.
Post by: bd on September 17, 2018, 06:44:17 PM

Refer to the 1985 Wiring Manual (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Wiring/ST_352_85_1985_Chevrolet_GMC_Light_Truc_Wiring_Manual_CK_10_30_Only.pdf#page=9).

There may be more than one cause precipitating symptoms.  Besides issues that are visually obvious, try to establish a known stable basis from which to work.  Disassemble, clean and verify ALL of the factory ground connections.  Poor grounds can cause nightmarish symptoms that evade all diagnostic logic.  Attempting to diagnose real wiring problems superimposed onto underlying poor grounds will drive you crazy and have you running haphazardly in overlapping circles.  Nothing will make sense.  For more information see the topic Ground (http://forum.73-87chevytrucks.com/smforum/index.php?topic=35756.msg301879#msg301879) in the Technical Forum.  Once you have verified that the ground connections are perfect, you can begin to methodically check individual circuits for more elusive wiring issues.

Title: Re: Only head lights are working!.
Post by: robosmurf on September 23, 2018, 08:57:03 PM

I had something like this in my 84. I found a spot on the headlight switch that had shorted or overheated or melted and left a big carbon booger next to the rotary dimmer. I was able to take the switch all apart then properly clean and lube it. There was a blown fuse that I replaced and everything worked good.

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