High beams stuck on?

Power4

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May 10, 2004
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Rochester, NY
I just got back from a drive in the Mustang a little while ago and noticed that my high beams are now stuck on, even if the car is shut off. I tried switching the positions of the headlight switch and pulling the high beam/low beam stalk but it has no effect, the high beams still stay on. So for now I've just disconnected the battery. Any ideas what could be wrong? Could it be a relay maybe? :shrug:
 
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Power4

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May 10, 2004
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Rochester, NY
So I bought a new relay for the high beams and replaced the old one. The high beams still stay on despite the car being off. Needless to say it wasn't the relay then.

Maybe the switch?

I think it must be the switch then since it wasn't the relay. The high beam indicator on the dash stays on even when the car is off and the high beam relay is removed. Where is the actual switch located, in the steering column at the base of the high beam/turn signal stalk?

One strange thing is when I pull on the high beam stalk and hold it back the high beams turn off (but come right back on as soon as I let go). Could this just be a result of a bad switch?
 

Power4

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May 10, 2004
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Rochester, NY
It sounds as if the switch that is supposed to click on and off as you pull the stalk back and release it isnt "undoing" its connection to switch off.

That's what I would think too but it seems to be moving properly and it's not making any strange noises. :shrug:

Replace the switch that controls the on/off and fog lights.

How does that switch affect the high beams?
 

mustangford289

Founding Member
Sep 16, 2001
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switch

That switch is the circuit that powers the headlights and fog lights. The lever on the column only activates a higher level of output, which seems to occur, for the high beams.
 

Power4

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May 10, 2004
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Rochester, NY
I went to play around with the Mustang some more to see if I could figure out if it is the switch causing the high beam problem. I removed the switch from the console (comes out very easily, just put a putty knife or blade beneath the bottom part and pry out). Unplugged the two plugs in the back and then back in again. Reconnected the battery and put the high beam relay back in. I noticed the high beam indicator was off before I even started the car up. After starting it up I tried switching the headlights to all the different modes and it seemed to work fine. The headlights flickered initially but seemed to be okay after that.

Does that indicate that it is indeed the switch going bad and/or a loose connection to the switch?
 

Power4

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May 10, 2004
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Rochester, NY
Hmm, after a few weeks the high beams are starting to act up again. They seem more prone to get stuck on if it's colder out which is usually at night. I tried removing the switch from the dashboard again, unplugging the plugs from the back and then back in again. However it doesn't seem to have an effect now. The high beam indicator stays on when the headlight switch is completely unplugged and all other lights come on as well. Does this mean anything or would the high beams come on anyway if the light switch is unplugged?
 

Power4

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May 10, 2004
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Rochester, NY
I've replaced the headlight switch with a new one and it's still doing this funky high beams stuck on thing. Typically after the car has sat for a few hours and they stay on for a few minutes after it's started up. So now it has a new high beam relay and a new headlight switch. What else is left that could be malfunctioning?
 

xdod

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May 15, 2021
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Hello. Nothing like resurrecting a 10 year old topic, huh? I have a 09 Mustang that is doing the same thing. Did you ever find solution?

Thanks,

Jim
 

Bullitt95

10 Year Member
Jun 13, 2007
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Have you had any water leaks into the passenger side footwell? It's possible the SJB has been contaminated causing corrosion to some of the terminals in the fuse/relax box.
 

xdod

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May 15, 2021
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Have you had any water leaks into the passenger side footwell? It's possible the SJB has been contaminated causing corrosion to some of the terminals in the fuse/relax box.
Hi Bullitt95! Thanks for the quick reply. I just bought the car last week, but I don't see any indication of water damage. Upon trying to trace this down, starting at the headlamps and working backwards through BEC, it takes me back to the SJB. Starting at turn signal switch also takes me to SJB as far as I can tell. I pulled it out and found a nest of bare wire connections, so that may have been it. I have ordered a used SJB with identical P/N and Kit number, so we'll see.

Do you happen to know if it will need reprogramming? I do have FORscan and the OBD2 connector, if necessary.

Thanks again,

James
 

Bullitt95

10 Year Member
Jun 13, 2007
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Hi Bullitt95! Thanks for the quick reply. I just bought the car last week, but I don't see any indication of water damage. Upon trying to trace this down, starting at the headlamps and working backwards through BEC, it takes me back to the SJB. Starting at turn signal switch also takes me to SJB as far as I can tell. I pulled it out and found a nest of bare wire connections, so that may have been it. I have ordered a used SJB with identical P/N and Kit number, so we'll see.

Do you happen to know if it will need reprogramming? I do have FORscan and the OBD2 connector, if necessary.

Thanks again,

James

The SJB is just a box full of fuses and relays so there's nothing to reprogram. Just disconnect both battery terminals before you swap in the new one.
 

xdod

New Member
May 15, 2021
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The SJB is just a box full of fuses and relays so there's nothing to reprogram. Just disconnect both battery terminals before you swap in the new one.

Ah, good deal. That makes it easier. Thanks again for the assistance.