Does the multi-functional switch control the brake lights?

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Dale 2001 TJ

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Good evening everybody ,

First I’d like to say Thank you all for you help in the past I’ve been able to get all the lights working on the Jeep except the brakes with your help , with that said my question is “ does the multifunctional switch control the brake lights ? As I have replaced several parts . The middle brake light is working by the way as well as turn signals . Flashers and running lights / reverse lights …
 
Dale 2001 TJ said:
Good evening everybody ,

First I’d like to say Thank you all for you help in the past I’ve been able to get all the lights working on the Jeep except the brakes with your help , with that said my question is “ does the multifunctional switch control the brake lights ? As I have replaced several parts . The middle brake light is working by the way as well as turn signals . Flashers and running lights / reverse lights …
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No, the brake light switch on the pedal under the dash controls those.

You need to check the bulbs and wiring carefully if the middle brake light works- the brakes come in on the drivers’ side I think and split off- that likely is where you may have a failed connection.
 
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AndyG said:
No, the brake light switch on the pedal under the dash controls those.

You need to check the bulbs and wiring carefully if the middle brake light works- the brakes come in only on one side then split up- I can’t remember which side is the primary but I knew 2 months ago.
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Thank you for answering , Ive replaced the brake light switch as well , taken the bulbs out replaced them and put new bolts ( 3 ) in each housing to tub for the ground , double checked wiring harness and cleaned as well as reaching the 20 amp fuse in the panel , oh and I took off the ground for the trailer harness making sure it had a good ground as well …..
 
Dale 2001 TJ said:
Thank you for answering , Ive replaced the brake light switch as well , taken the bulbs out replaced them and put new bolts ( 3 ) in each housing to tub for the ground , double checked wiring harness and cleaned as well as reaching the 20 amp fuse in the panel , oh and I took off the ground for the trailer harness making sure it had a good ground as well …..
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@mrblaine knows his way around these very well and is on the cutting edge with some tail lights he designed....maybe he can chime in -

Does any fire go to the brake circuit on the trailer harness?
 
Dale 2001 TJ said:
Thank you for answering , Ive replaced the brake light switch as well , taken the bulbs out replaced them and put new bolts ( 3 ) in each housing to tub for the ground , double checked wiring harness and cleaned as well as reaching the 20 amp fuse in the panel , oh and I took off the ground for the trailer harness making sure it had a good ground as well …..
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Do you have output power to the brake light circuit at the brake light switch? I don't know about the MFS being in this circuit, but I can think of no reason why it should.
 
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mrblaine said:
Do you have output power to the brake light circuit at the brake light switch? I don't know about the MFS being in this circuit, but I can think of no reason why it should.
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I haven't looked at the wiring diagram lately, but I would assume there's only one brake signal going to the back.
So, if one light works, your issue is in the back (not the front).
More than likely on the driver side where it splits.
Also, the turn signal and brake are the same, so ground is good.
YRMV
 
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the brake circuit does go through the MFS, since the turn signals and brakes share the same bulb filament. The brake switch feeds to the MFS and either passes straight through to both bulbs, or if the turn signal is activated, the brake passes through to the inactive side, and breaks the active side so it's powered by the flasher instead.

So yes, the multifunction switch plays a role in brake light function.

This schematic is for my 06, some details will vary year to hear but the principle holds.
1000001192.png
 
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Thanks for chiming in gentlemen.

Does seem if the third one lights up the signal
Is making it to that lead but not the corners- surely that 3rd light is not on a dedicated run (?) from the switch
 
I would use a 12V test light on the L and R side sockets when the pedal is depressed to verify that you do or don’t have power to these. If not I might consider the MFS if the schematic provided is correct. I don’t see the 3rd brake light in the schematic. If you have power then go to the ground sides of the sockets and start checking for continuity
 
Switched to my laptop now, so I have access to the 01 FSM. As in the 06 wiring diagram above the feed from the brake lamp switch goes to pin 1 of the multi-function switch on a white/tan wire. You should have 12V there when the brake pedal is pressed.

If you don't have 12V at the white/tan wire at the switch connector there is a break in the wiring between the brake lamp switch and the multi-function switch.

If you do have 12V on that wire there may be an issue inside the switch.
There should be continuity between pin 1 and pins 4 and 5.

Pin 4 is the output to the left rear turn signal where the dark green/red wire goes.
Pin 5 is the output to the right rear turn signal where the brown/red wire goes.

In the switch is put in the right indicator position there should be continuity between pins 1 and 4.
If you position the switch in the left position there should be continuity between pins 1 and 5.
 
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jonny jeep said:
Switched to my laptop now, so I have access to the 01 FSM. As in the 06 wiring diagram above the feed from the brake lamp switch goes to pin 1 of the multi-function switch on a white/tan wire. You should have 12V there when the brake pedal is pressed.

If you don't have 12V at the white/tan wire at the switch connector there is a break in the wiring between the brake lamp switch and the multi-function switch.

If you do have 12V on that wire there may be an issue inside the switch.
There should be continuity between pin 1 and pins 4 and 5.

Pin 4 is the output to the left rear turn signal where the dark green/red wire goes.
Pin 5 is the output to the right rear turn signal where the brown/red wire goes.

In the switch is put in the right indicator position there should be continuity between pins 1 and 4.
If you position the switch in the left position there should be continuity between pins 1 and 5.
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Thank You , I’ve purchased another multi switch and installed it prior to this and that is how I got my turn signals and flashers back , However I took the MFS out agin and removed the harness only to find that the harness corner is missing its outer casing with that said all other functions still work , do you think the missing corner would affect the brake lights , its exposing pins one and two but they are intact and fitting tight to the mfs
 
Dale 2001 TJ said:
Thank You , I’ve purchased another multi switch and installed it prior to this and that is how I got my turn signals and flashers back , However I took the MFS out agin and removed the harness only to find that the harness corner is missing its outer casing with that said all other functions still work , do you think the missing corner would affect the brake lights , its exposing pins one and two but they are intact and fitting tight to the mfs
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With that damage the piece that keeps those two terminals in place is missing. It may mean the contacts could be pushed back by the pins causing a loose or bad connection.

There is a repair kit available so you could replace the plastic part and maybe replace the two terminals where the damage is.

Part number is 5183442AA. It does cost a bit, but if you can find a Neon in a salvage yard, I believe they use the same connector for the doors.
 
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jonny jeep said:
With that damage the piece that keeps those two terminals in place is missing. It may mean the contacts could be pushed back by the pins causing a loose or bad connection.

There is a repair kit available so you could replace the plastic part and maybe replace the two terminals where the damage is.

Part number is 5183442AA. It does cost a bit, but if you can find a Neon in a salvage yard, I believe they use the same connector for the doors.
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Thank you for your help, I’ve ordered the harness replacement off amazon for 87.00 however its a two week wait , so to be continued ….. thank you again and to everyone else that has responded id appreciate it
 
LONGJP2 said:
I haven't looked at the wiring diagram lately, but I would assume there's only one brake signal going to the back.
So, if one light works, your issue is in the back (not the front).
More than likely on the driver side where it splits.
Also, the turn signal and brake are the same, so ground is good.
YRMV
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Have to go through the diagrams. The HMSL (3rd brake light) is odd due to having its own ground that runs to the tail gate contacts. The brake and turn pick up their ground at the tub.
 
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