I've got a strange problem with my brake lights on my '89 F-150. My brake lights only work when I use my turn signals. I have yet to perform any troubleshooting other than viewing an electrical schematic, but according to the schematic I am viewing the brake switch goes into the multi-function switch. From there it passes to the brake light itself. Has anyone else had this problem and do I need to replace this multi-function switch and if so, where is it located?

 

Have you checked the bulbs?

 

It may be a grounding issue. Beings they work when using the turn signals, I assume they ground somehow through the front turn signal bulb assembly. If your headlight dimmer switch is on your turn signal arm, that is your multi-function switch. If you have an on the floor headlight dimmer switch, you don't have a multi-function switch. Either way I believe the brake light signal travels through the turn signal switch.

 

Well mine is on the floor, and Im having the same problem. They seem to light up fine with the signals, High and low side of the bulb. The Boo switch is fine, and another thing that does not work, is the hazard switch. But... if I pull the hazard switch, the turn signals wont work. So I'm assuming the hazard switch works? And the book I have says it comes from the fuse box, to the hazard switch and the boo switch, and from each switch, they have their own wire running back to the directional switch. And yes, my fuse is ok...

 

ok heres another weird point.... The line side of my fuse is putting out .2 volts... ????? how is that possible? I see no wire there.. maybe the fuse distrubiton block shorted ?????? There should be some kinda 12v there

 

so your all stumped huh? lol I like it.. my kinda problem! Nothing good is ever easy.

 

this is all i have to look off of...

 

well... from the looks of the other diagrams, my turn signal switch is more or less the same thing w/o the high beam selector. From the looks of it, none of the wires in question are grounded.... so why does that lt green / red show 60 ohms ? this meter has taken a bit of abuse, but it reads open / and 0 just fine... Maybe the 60 is the resistance of the two rear bulbs in the brake lights them selves before they get to ground. How many watts are those bulbs ? Math tells me 2.5 amps per bulb,
60watts / 2 bulbs = 30 watts a bulb
30watts / 12volts = 2.5 amps

Assuming 2.5 per brake light, and front signal, thats 10 amps, not counting the parking lights, which are dimmer and I would assume a lesser wattage, maybe 1.5 ? But add that up, your talking about 16 amps on a 15 amp circuit.... In building code your only supposed to rate circuits @ %80, that would be 12 amps.. but those numbers arent working out...

Ford dealer has to order that directional switch, and it will be like wednsday at the earliest before they would get it.. what a buncha crap... I want to get full coverage on it, and push it in the river... get a new one.. lol

 

OK... now im really stumped.. lol kept testing ****, and i put it all back together... if i put 12volts on the brake light switch itself it works like it should, and the hazards work.... so my origional question stands.... is it possible the fuse block itself could have a problem? I'm out of ideas...


I thought some of you guys were smart... and no one has a clue? Or are you all just too lazy to type?

 

I do have the dimmer switch on the floor and have FINALLY had time to troubleshoot this problem further. First off, my rear hazards do not work either UNLESS I turn on the directional indicators. Additionally, my cruise control is no longer working. This made me very suspicious of the fuse, being the hazards, stop lights, and cruise control are all on the same 15 amp circuit, but nothing there. It makes no difference if the dimmer switch is in high or low. There is no damage to the wires in my steering column at the directional indicator switch. Does anyone have any other ideas where to troubleshoot???? Please Help!!

 

Well I dont have cruise, but I will tell you what I did to make it work. I snipped the wire coming from the fuse panel going to the brake switch. Ran a new wire from the battery, thru an inline fuse, straight to the brake pedal wire I snipped. Everything works now like it should. Now that I think about it, the terminals on the brake pedal switch are a pushon terminal. You should be able to pull the one off, and if u ran another wire, crimp on a terminal, then it would kind of be a plug and play thing.

I have this question up on 4 other forums, and no one knows besides the turn signal switch, but I think its funny that it works now. And no one has an answer yet. Just lettin ya know what works. FWIW, I would not splice into that wire, but cut it all together. I did because if the power wire is shorting, then it will still be shorting, and I dont like vehicle fires.

 

I attempted to send 12V directly from the battery to the brake switch with no luck. It seems like a good solution especially being the function giving me issues are tied to the same circuit and makes me suspicious of the fuse block. Any other ideas??

 

Did you try both sides of the switch? What i did was pull the hazard, and figured out which it was... (could hear the relay clicking) But another thing I thought of... was that fuse block.. I posted about it in my SHO Forum, same fues block as in my 92 SHO, to see if the fuse blocks themselves can develop a short. That would be the first one to go I would think, with the constant, on / off thing, i cant think of another circuit that would get more abuse, or use. Mine is still working but I hate rigging stuff like that.

 

Yes, I attempted to apply 12V to both sides of the brake switch. I am not 100% sure, but I believe the top side of the switch the was the side that needed constant 12V. After doing some more searching, I am beginning to wonder if I need to replace my entire turn signal assembly or maybe my hazard switch. The brake light signal needs to travel through the turn signal and I am unsure where the failure could be there?

 

Well, I finally have solved my brake light problems. I just yanked the whole signal assembly from the steering column. The part ran me about $55 and took about an hour to install, but brakes, hazards, cruise all work like a charm. I haven't had a chance to dissect the old turn signal assembly to see what was the problem, but hope to soon! Thanks everyone for any help!