Wiring diagram for 1990 GMC Sierra ?
 

I am trying to find a wiring diagram for a 1990 1500 GMC Sierra truck. Does anyone know if there is a wiring diagram available on the internet? I have a friend who has this truck and the headlights and parking lights and tail lights do not work. Some Yo Yo replaced the headlight switch and the lights worked for a short time and then went out. I am an Electronics Technician so I am used to using a wiring diagram to trouble shoot electrical problems. Guessing just doesn't get with the program when working with a 100 amp battery/charging system. And NO, I don't charge to help people with electrical problems. I am retired, and helping folks gives me the sense of being worth something to others. Doesn't cost me anything to help others. :) Thanks for your attention!

~ Don ~

Post yor email address and I will send you a picutre of it.. Thanks.

If you still need this I have the entire schematic that I can scan and send to an email address.

Rich :burnout:

Rich and Lowgrn1, my email addie is dodson@vnet.net I just looked at my profile and saw where it didn't include my email address. Gonna have to see about getting my email addie in there. Thanks fellows for your help.

~ Don ~

:p That's what I'm doing too. I will send it to, just in case you don't.

Email sent. Just let me know if it don't work out.

Lowgrn1, I got the schematic and it will get me started. I see from the diagram that fuse 9 labeled parking light fuse, (20 amp) goes to the headlight/panel dimmer switch, and from the switch it goes to a junction point where it brances out to the the parking lights, license light, and cab clearence lights and also the headlight system & interior light system. I can now go to the headlight switch and see if +12 volts is coming into the switch.
Once the voltage gets to the headlight system I am sure it will go into the headlight dimmer but hopefully the problem be prior to that point. You have provided me with a real clue of where to go and what to probe. Thanks so much, and I am gonna show the lady who owns the truck the messages and email that others have submitted to help get her headlights and parking lights working. Thanks so much for your assistance. Wow, and the humidity and heat is gonna be high today. Shade tree mechanic today :lol:

~ Don ~

Your Welcome. No problem at all. A picture is worth a thousand words.

Thanks Lowgrn1, I got caught up in a project that took way more time than I expected it to. Appreciate you covering my back. I got it scanned but didnt get it in the mail. L8R

Rich :burnout: