Weird electrical issues

[Zukinut]

1968 f350.

So as I've poste on here before, my headlights turn themselves off and on at will. Many states this was common and that the switch should be replaced. I'm cheap and just try to not drive it at night, haha.

Well this morning it was 30ish degrees out and the heater blower motor started turning itself on and off at will. No rhyme or reason. Is this common also or am I correct in thinking that the headlights and blower might be on the same ground that isnt solid anymore. Maybe a loose ground is causing all the problems.

Thanks for any and all help.
Will

[72BahamaBlue]

I had a bad high beam switch that caused the headlights to go out, might be worth checking.
*edit* Sometimes a good stomp on the dimmer switch get the low beams working again...for now! If the dash switch is original, might be time to replace it.

The heater switch on nearly all the bumps I've owned needed a litte wiggle up and down to get them to work.

[bluef250]

Two electrical problem areas may cause the problem. The fuse box may need attention or the ignition switch. Before digging in check all the grounds.

[tac]

Second on the floor dimmer switch. It will do this, trust me. Doing 70 out in the middle of nowhere heading towards a narrow bridge with no moon and click!

[1972hiboy]

Second on the floor dimmer switch. It will do this, trust me. Doing 70 out in the middle of nowhere heading towards a narrow bridge with no moon and click!

Yeah no kidding. Had my 10ft cabover on my truck and I was climbing the winding part of hwy 49/108 into the sierra foothills late friday night to get a head start on the weekend round a turn and sure enough, "click" nothing. scared the beejeesus out of me. turned out the marker lamps on the camper were to much of a load for the headlamp siwtch and it tripped the built in breaker on the switch. Apparently pulling over to clean the beejeesus out of my pants was enough time to cool the switch and the headlamps came back on. But food for thought maybe the switch is heating up and tripping the breaker.

[Zukinut]

I bypassed the dimmer switch, didn't fix the problem.

Has anyone had an issue with the blower motor turning off and on. I can't find anything on that, I also don't see a wiring diagram on this sight for it.

Will

[tbone6]

Has anyone had an issue with the blower motor turning off and on. I can't find anything on that, I also don't see a wiring diagram on this sight for it.

Will

You might want to try the 67 master or the 69 diagrams. They should be close enough to get you in the ball park.

[two-bit]

Blower motor ground wire connects at heater box. If its dirty/corroded/ect, you will loose ground for blower motor. Pull glove box, look for black wire with loop connector under a sheet metal screw on the heater box. Take it off, clean it up, consider another ground source when the sheetmetal screw doesn't seem to ever get tight when you go to put it back in. (Don't ask how i know) I think i eventually grounded mine to the dash....somewhere. Never had a problem with it again.

Headlamps..prolly switch. If you have added on cab lights or other markers, feed them w/ a relay. Factory switch does not like extra load.ie: 72Hiboy's example

My '72 F-350 has the factory relay in the harness for the cab clearance lights.

Two-bit

[Zukinut]

Interesting, I don't think my 68 has that relay.

I'll take a look at that ground.

Thanks again
Will

[Zukinut]

Edit--my truck does have the relay for the marker lights. The po has bypassed it tho. I found how he bypassed it for the side markers but haven't found where he bypassed it for the top clearance lights.

The new ignition switch also crumbled as soon as soon as I put my hand under the dash. That could be a part of the problem too.

Will

[Zukinut]

Hooked the factory relay circuit for the marker lights and that seems to have fixed the lighting problem.

I'll repost in a few days and let everyone know.

Will

[two-bit]

Good luck your way.
I had a cheapo Auto Zone replacement ignition switch do that to me years ago. Whilst out at deer camp.
Went to a local parts store...55 miles away. They didn't have one. Guy at the counter says, let me make a call.
20 minutes later a very big, burly looking guy comes thru the door. Local Ford truck guru.
He brought both switches with him, bullet and blade.
Swapped out my key center, paid him $10 for the switch. drove that truck for another six years. Never had a problem with that ignition switch.
Took my old one back to Auto Zone when i got home. Some well placed words with management, and i got my money back.
Nothing like OEM parts.

[Art]

Nothing like OEM parts.

That is an understatement!

The headlight switch has a circuit breakers built into it to protect the headlight circuit, so that could be a possible cause of lights working, going out, and then coming back on a few seconds later when the breaker resets itself. Those breakers can go bad over time when loaded heavily.

The heater circuit is protected by a fuse, so it wither works or doesn't. There must be a bad connection in the circuit. I did have a switch go bad on me with one of my trucks. When wiggling the switch lever around, the heater motor speed changed - indicating a poor connection within the switch. I installed a different switch from a parts truck (again, OEM parts) and it never gave a lick of trouble again.