Fuse 13 - brake lights - direct short (Solved)

[DHBWA]

Helping my MIL…1995 Explorer Limited.
She has owned it since new. Never wrecked nor modified. Started intermittently blowing fuse 13 to brake lights. Now it blows as soon as you step on the pedal. I visually inspected and disconnected all the rear brake light bulbs (including the HMSL), disconnected the entire trailer wiring, replaced then double checked stop light switch (2 wire), disconnected the master cylinder switch and visually inspected under hood wiring.
Still blows fuse instantly…

What have I missed….?
Thanks in advance!!!

 

[Fix4Dirt]

Helping my MIL…1995 Explorer Limited.
She has owned it since new. Never wrecked nor modified. Started intermittently blowing fuse 13 to brake lights. Now it blows as soon as you step on the pedal. I visually inspected and disconnected all the rear brake light bulbs (including the HMSL), disconnected the entire trailer wiring, replaced then double checked stop light switch (2 wire), disconnected the master cylinder switch and visually inspected under hood wiring.
Still blows fuse instantly…

What have I missed….?
Thanks in advance!!!

welcome to EF! does 13 also control the cruise control stuff? if so have ya had the recall done? may be internally shorted not aure. iirc i think mine did that years back but not sure which fuse powers it

 

[DHBWA]

Thanks and I can’t remember if it does but I did notice an odd additional factory wiring on the master cylinder switch which I am 90% confident is that recall.

 

[Fix4Dirt]

Thanks and I can’t remember if it does but I did notice an odd additional factory wiring on the master cylinder switch which I am 90% confident is that recall.

cool alright... let me see if i can come up with anything else

 

[J_C]

With both left & right brake light bulbs removed, I'd take a multimeter and measure resistance between the bulb socket positive and ground contacts. You don't need to be pressing the brake pedal for this test. Resistance should measure very high (if the 3rd brake light ballast conducts some) if not infinite.

I'm wondering about the positive wire to them shorting out somewhere, or possibly where it also goes into the connector for the multi-function switch on the steering column, the contact might have pulled out the back of the connector and be shorting there.

I'm not sure if a ballast failure to your 3rd brake light above the lift gate could cause a short like this but if all else fails, I'd unplug the 3rd brake light to see if that's it.

Wiring diagram attached.

 

[DHBWA]

Thanks. I did disconnect the 3rd brake light on my initial check. I fully expected the problem to be it…..
Still blows fuses.
I will check resistance.
Appreciate all the comments!!!

 

[DHBWA]

J_C - are you confident that is the correct diagram? Interesting in that the power wire also feeds the RAP module. I also need to determine if it has a “lamp out warning module”

 

[J_C]

^ No, not anywhere near 100% confident. It's just what I have, some wiring may change from model year to model year but besides the LOM and RAP it is a pretty basic circuit, doubt it changed much.

Lamp out warning module (LOM) is in the center console stack (below the radio) if you have it, so it lights up if a sensed bulb circuit has insufficient current. You can probably just ignore it, just keep tracing the light green wire. Generally a fault with the LOM stops the lights from working, not blowing a fuse. At the same time, as with the RAP module, if there's a short in the wire it could still be on the route to it.

To rule out the RAP module you can simply unplug it (is behind the left rear trim panel in the cargo area, can be seen with the access panel off) but i doubt you need to bother - the power isn't going TO the rap module over that wire, rather the RAP module has its own power lead on a different fused supply and outputs power TO the brake lights over that wire, so a faulty RAP would tend to blow the other fuse it's on, not fuse 13. *I reserve the right to be wrong.*

Won't hurt anything to unplug it for testing. On the other hand it could still be a short in that wire going to the RAP module, since it's live to it along with the bulbs when the brake pedal is pressed. Also keep in mind that if you activate the RAP and it tries to flash the brake lights, and there is a short in the wiring, that could blow the RAP's separate fuse.

 

[DHBWA]

Thanks again. I am going to do another visual tonight……….

 

[DHBWA]

VICTORY
Light green power wire was disconnected from the plug going to the turn signal switch and shorting out on column. The switch had been replaced at one time. Poorly….
Now the radio…..Made removal tools from a coat hanger and had it out in a minute. Cool! Got numbers and popped it back in and now I can’t get it back out. Worked for an hour and gave up for the night. Going to break down and buy the tools and pray…

 

[J_C]

Glad it's sorted out. Several people have had the wires pull out of that, don't know if it's more common for people who adjust their tilt steering or something. Some people fortify the connector by putting some hot glue or epoxy on the back to hold the contacts in.

Radio... find a stiffer coat hanger?

 

[DHBWA]

Radio... find a stiffer coat hanger?

Maybe but for $6-$8 I’ll try the tool. What was so frustrating is it popped right out the first time just using tools made from a coat hanger….Of course I got lots of help/suggestions when it wouldn’t come out the second time 10 minutes later……

 

[Pete Deering]

Thanks and I can’t remember if it does but I did notice an odd additional factory wiring on the master cylinder switch which I am 90% confident is that recall.

That the recall fix for the master cylinder wiring fire