2005 f150 xlt. after replacing highbeam fuse they are not working well. I can run the highbeams for about 2 minutes then my headlights completely shut off until I turn the highbeams off. I replaced it with the same size fuse, 20 I believe. Only thing I can think is the new sound system is pulling to much power to run the high beams but iv had many other sound systems in other cars not cause a problem even running much higher watts.. The new amp pulls 300 watts rms. Any ideas?

 

Turn the flippin' stereo off!!!

 

Why did you need to replace the fuse for the high beams in the 1st place ?
- It is not so much the problem happened after replacing the fuse, but the 1st time the fuse blew is what is causing the problem.

Aside from the sound system are there any modifications such as after market bulbs or an HID kit ?

Did you accidentally use the high beam fuse for something in the sound system ?
- Does the sound system go off when the high beam fuse blows ?

How much did you remove in getting the new sound system installed ?
- Questioning if there is a problem with the factory wiring such as a wire got pinched when the sound system was installed.

 

the high beam fuse never blew I pulled it and put it into a different fuse that was blown but more important at the time. no modifications to headlights. sound system does not go off when the headlights shut off. ran most wires under the carpet and nothing much up around the steering column or fuse box during install (which I assume is where any highbeam wires may get pinched). ran the wires down the right side of vehicle on floor.

 

Sorry for the delay in the reply, this now has me scratching both ends wondering what is going on.

Dumb question time for me, do not take it as an insult.

Did you replace it with a 20A fuse ?
I think all 20A are yellow, and a screw up in the dark the next closest one would be that tan-ish one, which is a 25 A.
Did you get a good seating on the fuse ( not the blade pushed away the fuse socket and?

- I told you it was dumb question time for me.

Next question I did not ask before, your post was "then my headlights completely shut off until I turn the highbeams off. "
Is this just a flip of the MFS ( Multifunction Switch aka turn signal stalk ) or something else ?

Diagnoses step and it is going to sound stupid, unplug one of the bulbs and see if the high beam fuse holds.
- Trying to figure out what load is causing it to pop.

This is an interesting one, being nowhere near the MFS, main headlamp switch or the fuse panel on the passenger side.

 

Yes its a 20 amp. I will try to pull it and make sure it plugs in correctly. and yes the MFS switch. I just pull it back for 10 or 20 seconds then I can turn on the beams again. Almost like its recharging itself.

 

That's an overheated connection that had opened up that's subsequently cooling down and reconnecting (temporarily, until it heats back up again).

 

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