I replaced traditional incandescent brake light assembly with LED lights. They required no wiring harness modification. After a few months ago the head lights in my 2003 f350 went out and turn signals began to malfunction. It has utility boxes. I resolved the turn signal issue today by replacing the hidden relay, TBB89. However the head lights still aren't functioning. When I turn the headlight switch the dashboard lights function. Except the high beam indicator is on constantly no matter the position of the switch on the steering column.

My bother believes the LED swap is a possible cause of the simultaneous malfunction of the headlights and turn signals. (Im not convinced that thats true but he's an electrician and avid Cummins modder so I thought it might be good to add his two cents.) Personally I think the switch in the steering column is the issue and that the turn signal relay and headlight failure just happen to coincide.How do I go about testing the column switch? And if the LED swap is the culprit how can I prevent this from reoccurring?

What do you guys think?

Thanks!!

UPDATE: Tail light issue has been resolved. I have replaced switch of the column but the head light issue still exists.

 

I would get some cheap 9007 halogen bulbs and plug them in to see if the problem stays with the truck, or if it leaves with the LED bulbs.

If you don't have access to 9007 bulbs without purchasing them, maybe borrow a multi-meter from your brother if you don't have one and test the OEM connectors/plugs for power when the switch in the cab is set to low beams.

 

would I be looking for a specific amperage or voltage? I have taken care of the turn/brake light problem. am having trouble with head lights still.

 

Neither low nor high beams work? I seriously doubt putting LED tail light bulbs in caused the headlights to fail. It's more likely that the multifunction switch went bad.

 

I would suspect that the voltage would need to be around 12 or so to fire the lights. Pikachu knows a lot more about these trucks than I do, but testing the connectors is an easy way to isolate the problem to the harness/switch or the bulbs themselves.

 

can always go back to the previous tail lamps and see if the issue stays or goes away, in short of that I am in agreement with the MF switch being bad, its at least a good place to start. I would replace the switch and see what happens, worst case is the issue still persists, and you *might* (I say this loosely based on the fact I have done a few LED conversions and I am in the process of converting the truck, and Mustang as of this post) need load resisters.


Do you know if your LED replacements have built in resisters? check the documentation and see if they require/recomend the use of load reststers...that might be another source of the issue, but start with the MF switch as far as the high beam failure as I can say that most likely is the issue with the high beams indicator and lights not working as expected!

 

Here is how to test MF switch. Hit the arrow to get the other tests.

Ford Truck Picture by carltonwebb | 852082 | Ford-Trucks.com

 

Just got done swapping the MF switch. Still no headlights. Still getting an indicator on the dash saying brights are on no matter the position of the MF switch.

 

not sure on the 03, but the 02 has a lighting module.
when the module on my 02 went bad i lost headlights.
i had the dealer fix it and the guy i bought it from paid for the repair because it was still under warranty.

 

Where can I find the Control Module?

 

like i said, i have no idea where it is except under the dash somewhere. it was still under the used car warranty offered by the seller so it just took it to the dealer and let them deal with it.