No Low-Beams '94 f150

Okay, I'm looking at the wiring diagrams on

But when I flip the main switch from parking lights with no headlamps to WITH headlamps, the parking lights flick off in between locations on the main switch, indicating to me that it recognizes the switch to headlights.

MW

A clue! Maybe when the multi-function switch was replaced, one of the wires didn't terminate tightly? Came loose when you weren't lookin'. More likely than a faulty new switch, but with parts these days....I wonder what was wrong with the old-time high/low headlight floor switch? Prolly too reliable....

Dave S(Texas)

spoken like a Texan (smile). They have a problem of shorting out in northern climates, something to do with snow and salt being tracked into vehicle in winter months. Also corrosion issues for the same reason. Dodge had some serious problems with fires because of that in the mid 70's to early 80's to the point that while in the service we were issued a "modification work order" to ether remove all the insulation from the floor mats, or remove the floor mats completly for all M880 and M890 series 5/4 ton Dodge trucks.. All they did is move the darn thing up on the steering column and run a rod down to it from the stalk. I replace a lot less highbeam switches since the move was made. Another easy money repair lost.

Whitelightning

I just cannot believe it..... Both bulbs burnt out at the same time. Went to the local parts store, bought new lamps, threw 'em in... bingo. I am relieved, but bewildered. Maybe God graciously did this so I could replace both at once instead of making two trips, I dunno. =)

Thanks for your idea bout the switch, I had the same thoughts running through my head about whether they did it right or something.

MW

Maybe all that voltage that was able to pass thru a good MF switch was more than the old darlin's could handle!

Lugnut

I do believe you just learned O'Brians' Law.

Whitelightning

You said that you had the low beams on when you shut the truck down. OK, you probably turned them off before you shut off the ignition but for both to burn out at the same time indicates a power spike thru the bulbs. It may have been a "one-time" event or it may be a symptom of other problems. If the same thing happens again in the not too distant future, I would suspect the switch that was recently replaced.

Dave D

I'm curious about this: where/how in a 12v system could this 'power spike' occur and why did it affect only the low-beam element in the headlamps and no other electrical component of the vehicle?

LOL...good one!

Dave S(Texas)

If they were the only components energized thru the suspect switch and the power spike was cause thereby, they would be the only component affected. Quite simple when you use a little thought ,

Dave/Trudy....your knowledge of electricity/systems is astounding. Your 'little thought' process is common to all DIY's....wtg

Dave S(Texas)

I had this problem many years ago on a '70 Plymouth. No low beams, but the high beams worked fine. Spent a whole weekend in the driveway with a meter tracing down the wiring, switches, etc., and could not find a wiring problem.

Finally discovered the problem. Both low beam lights were burnt out. Could never happen again in million years having both burn out at the same time, but it did.

RCE

Heh. I should have read a few more posts.

Congrats! I thought I was the only one on earth that ever had that happen.

RCE

Anything in the circuit that has some inductive reactance (coil, windings, etc.) could cause a spike when the field collapses.

RCE