High Beams Stay On

Tiny
KURTHUEGEL
  • MEMBER
  • 1998 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 197,000 MILES
My high beams stay on with the light switch turned off and even with the engine off and key out of the ignition. When I turn on the light switch the high and low beams work correctly. I have changed the light switch assembly and the multi switch with no results.
Sunday, March 29th, 2009 AT 5:36 PM

9 Replies

Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
If you unplug the wire connector from the multi switch and the lights still stay on, you have a cross over short on either the GRY/YEL wire from the multi switch to fuse #16 in the fuse block OR from fuse #16 to the headlights.
If the lights DO go out when you unplug the harness from the multi-switch, the multiswitch is bad.
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Wednesday, March 31st, 2021 AT 7:28 PM
Tiny
KURTHUEGEL
  • MEMBER
  • 5 POSTS
I have removed most of the dash panels and have followed the wiring and have found no grounds or broken wires. The multi switch is removed and the lights are still on. When I remove the #16 fuse the lights stay on. Should they stay on? The wiring harnesses under the hood to the lights look good. I am at a loss unless the #16 fuse location is bad.

Thanks for the HELP!
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Wednesday, March 31st, 2021 AT 7:28 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
No, with the #16 fuse out, you should have no high beams at all.
Check both sides of the socket for #16 fuse. Are they both hot?
If yes, in the power box under the hood, pull #8-30amp fuse. Do all the lights go out?
Let me know.
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Wednesday, March 31st, 2021 AT 7:28 PM
Tiny
KURTHUEGEL
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  • 5 POSTS
I checked both sides of the #16 fuse and only the left side is hot. I did pull the #8 fuse under the hood in the power box anyway and the lights did not go out.

Thanks Again
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Wednesday, March 31st, 2021 AT 7:28 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
Well, that soots down my first theory. Is the high beam indicator "on" in the dash?
Do you have the DRL option on the truck? (Daytime running lights)
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Wednesday, March 31st, 2021 AT 7:28 PM
Tiny
KURTHUEGEL
  • MEMBER
  • 5 POSTS
Yes I do have the Daytime Running Lights option. Yes the high beam indicator light and the high beams are on when the light switch is in the off position. When I turn on the light switch I can change from high beam to low beam normally but as soon as I turn off the light swith the high beams and the indicator light turn on. It seems to me that it is the high beams and not the daytime running lights that are staying on.

Thanks
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Wednesday, March 31st, 2021 AT 7:28 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
OK, now it's starting to make sense. In your "power distribution block, unplug fuse #9-15amp. If the lights go out, your DRL module is bad. Check it out and let me know, Jim.
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Wednesday, March 31st, 2021 AT 7:28 PM
Tiny
KURTHUEGEL
  • MEMBER
  • 5 POSTS
Hi Jim,

Well that turned off the lights so it is a DRL module that is bad. How does that control the high beams? I guess I always thought the DRL were on low beams.

By the way were is the DRL Module located?

Thanks for all of your help.
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Wednesday, March 31st, 2021 AT 7:28 PM
Tiny
JAMES W.
  • MECHANIC
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According to the diagram, both hi and lo beams go through the DRL module. Why, I don't know. The fuse you just pulled is hot at all times and for some reason, that circuit in the DRL module has crossed over to the highbeam circuit.
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Wednesday, March 31st, 2021 AT 7:28 PM

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