where is the headlight relay on a 1977 gmc 3500

[bigdaddy4x4]

i bought a set of h4 headlights to replace the old ones on my 77 k3500 now they flicker on and off i can barley hear a clicking noise behind the left side of the instrument cluster but i dont see no relay

[kipps]

Originally Posted by bigdaddy4x4

i bought a set of h4 headlights to replace the old ones on my 77 k3500 now they flicker on and off i can barley hear a clicking noise behind the left side of the instrument cluster but i dont see no relay

As long as the truck hasn't been modified, there is no relay in the headlight circuit. The headlight switch operates the headlights directly.

The factory wiring diagrams are located here, if it helps trace down the problem. http://67-72chevytrucks.com/vboard/s...d.php?t=545416

[bigdaddy4x4]

thanks for the reply i have always had a 70s model trucks but never had to look for a headlight relay on them what throwed me off was the real faint sound of a relay clicking on and off when the headlights came on and off still dont know where its coming from i am gona buy a heavy duty headlight wiring harness from lmc when i bought the new headlights i didnt think i would have to change anything but to run them i got to change the wiring harness thanks

[Axle]

Thermal overload in the headlight switch probably.
Do your lights a favor and wire up an external relay harness for your headlights, might as well get the most out of those H4's.

[Getter-Done]

Found this Article.
This may help you.

Link: https://gtsparkplugs.com/headlight-relays.html