all lights go out after 10-20 seconds

[sharkdog]

Hi, all

I haven't had my truck on the road in at least a couple years but working on getting back on the road. anyway I've noticed when I pull on the headlight switch my headlights running lights tail lights(I think even the dash lights) come on for 10-20 seconds then they die. Just wondering where I should start first. I assume it's some sorta ground problem but is there one place I should check first? or is it something completely different?

Thanks

Pete

ps 1970 f100 2wd auto long box with 360/power steering

[bluef250]

Sounds like a heat problem from high currant draw or bad contact.

1, Circuit breakers in switch get weak. Light switches go bad. Use another switch to see if problem persists.

2. Trace each wire from switch to light. Often times insulation goes bad or get chafed creating a short/ground.

[cep62]

I've seen corrosion on the back of the fuse block .
I had to loosen the fuse block and repair the back side connection.

[sharkdog]

thanks, I'll see about inspecting the switch and maybe I can clean it before I go buy a new one to try.

[basketcase0302]

Sharkdog thanks, I'll see about inspecting the switch and maybe I can clean it before I go buy a new one to try.

Other than cleaning the spade terminals with contact cleaner I'm pretty sure you can't really clean the integrated circuit breaker INSIDE our headlight switches.
Something else I didn't see mentioned above is to go through your grounds.
1) Main ground cable to engine.
2) Ground strap from intake manifold to firewall.
3) Ground strap from steering column U-Joint from one shaft side to the other.
4) Ground wire at the radiator support, (where the headlight will get their ground from).

[zgerbic]

Another way to troubleshoot the headlight switch is to just unplug the connector and use a stranded ~14G jumper wire to jump from the 12V-in connector to the headlight-out connector. Wait 30 seconds. If the headlights are still on, the switch is bad.

Power enters the headlight switch on pin 25 (black with an orange stripe large wire) and leaves headed toward the dimmer switch on pin 15 (red with a yellow stripe large wire). So jumper those two together to bypass the headlight switch.

The power to the headlights passes through the dimmer switch. I would cycle the dimmer switch a few times to make sure the contacts are not corroded before doing any testing. If the headlight switch is good, try putting the dimmer switch in the high position and see if the highbeams stay on for 30 seconds. The lights should stay on regardless of which position (high or low) the switch is in.