No brake lights, pretty frustrated at this point

[saburai]

Yep, I have one of those too. Those are the reason we invented the term "POS".

I've since replaced it with a somewhat better POS from Frys.

I've got a little Chinese inductive multimeter that's really good. I've got a friend who's a electronics hobbyist who recommended it. It's apparently highly recommended by geeks. I'll find the amazon link after dinner...

 

[chillman88]

Alrighty guys, I've linked it SOMEHOW to the wiring in the column. Here's where we sit now as I'm trying to track down a wiring diagram for the crescent shaped connector that goes to the multifunction switch on the column.


1. Turn the ignition on taillights come on dimly. Ignition off, tallights go off.

2. Pulled all light/illumination related fuses (even ones that SHOULDN'T affect taillights) and disconnected the trailer relay. Taillights still on.

3. Brake switch tested fine, switches as it should. Brake switch pigtail has battery voltage on one side and ground on the other as it should.

4. Tested trailer connector. Lights OFF and ignition ON. Turn signal wires (both of them) have approx 6 volts.

5. Disconnected the harness to the column and the taillights went out.

I believe the issue is somewhere in the multifunction switch. I'd like to test it some more and see if I can fix it without replacing the switch, but I'll order a new one if I really think that will solve it.

I don't want to replace it and then find out there was a short somewhere else and I misdiagnosed it!

 

[Selahdoor]

Another question... Do you have an electronic brake control for a trailer brake? (Mounted to the bottom of the dash, usually.)

 

[chillman88]

Another question... Do you have an electronic brake control for a trailer brake? (Mounted to the bottom of the dash, usually.)

Yes/No. I have one of the older hydraulic ones. Has a hot in and an out to trailer plug. It's not connected to my brake light circuit at all like the newer electric ones would be.

 

[chillman88]

Posting this here for Reference. I'm going to go out and do a little more testing now that I have this.

You must be registered for see images attach

 

[dgr]

Good find on the circuit diagnosis diagram. It nicely shows how the feed through works on these little engineering marvels.

Did you pull the turn signal flasher? Key on it would seem that is where the power is coming from that is dimly lighting the tail lights. Could be dirty contacts in the hazard switch

 

[chillman88]

Did you pull the turn signal flasher? Key on it would seem that is where the power is coming from that is dimly lighting the tail lights. Could be dirty contacts in the hazard switch

Haven't tried that yet, good idea.

Here's my new problem.

1. Tried a different column just for kicks. Same dimly lit lights, but brakes work.

2. Switched back to the old column, same dimly lit lights, brakes WORK????

There's a very good chance that I'm going to be beating myself up for this one. My little sister was pushing the brakes while I was looking at the taillights. How much do you want to bet she was pressing the CLUTCH INSTEAD?

I'll keep an eye on it for a while. I don't have a problem with the dimly lit lights as long as it doesn't cause any problems. Banging my head against the wall that I was troubleshooting this the whole time if that was the whole problem.

That being said, they're working now so at least there's that.

 

[saburai]

Good help is hard to find...
Glad you *solved* it!

 

[chillman88]

Good help is hard to find...
Glad you *solved* it!

I don't know. She said she was pressing the brake not the clutch. It's working now though.

Nothing worse than fixing a problem without figuring out what was broken.

I'm hoping she had a blonde moment and really was pushing the wrong one but I don't know.

 

[dgr]

Hahaha. I had my wife (from a right hand drive country) press the brakes for me. Same result. I went and looked and she's pressing the gas.

She wanted to know why I was yelling from the back of the truck. Press the BRAKE pedal. Same layout as her Toyota Vio, just on the other side.

Is your hazard on the column? I'm real curious about the dimly lit lights.

 

[saburai]

Nothing worse than fixing a problem without figuring out what was broken.

That's for sure. Then you'll be wondering for ever...

 

[snicklas]

Also noticed that the led lights up very dimly as soon as the ignition is turned to run. Not bright, but must be some parasitic crossover somewhere.

OK, I know your truck is currently a ZF-5. Has it EVER been an E4OD? The TECA can illuminate the LED a bit wit the control current (which is why the LED's make the TECA mad)...... just a shot in the dark. If there is no TECA onboard, could it be the turn-signal switch in the column? I know they can cause issues, and in the later vehicles with the multi-malfunction switch can really reek havoc...... (like the turn signal stalk being broken in a 99-04 F-150 can make the brights come on randomly.......)

OK, On Edit, late to the game..... some of this has been mentioned.....

 

[IDIBRONCO]

As strange as it may sound, check for bad grounds and/or bad bulb sockets. These can make power back feed some how.

 

[chillman88]

Is your hazard on the column? I'm real curious about the dimly lit lights.

Sorry, I missed this post yesterday. Yes, hazards are on the column.

The spare column I tried acted exactly the same oddly enough. I might possibly try a new multifunction switch eventually though. If you think about it, even the least worn one I have is still 30 years old....

 

[chillman88]

OK, I know your truck is currently a ZF-5. Has it EVER been an E4OD? The TECA can illuminate the LED a bit wit the control current (which is why the LED's make the TECA mad)...... just a shot in the dark. If there is no TECA onboard, could it be the turn-signal switch in the column? I know they can cause issues, and in the later vehicles with the multi-malfunction switch can really reek havoc...... (like the turn signal stalk being broken in a 99-04 F-150 can make the brights come on randomly.......)

OK, On Edit, late to the game..... some of this has been mentioned.....

It could be the switch, see my previous post if you haven't yet.

I have no reason to suspect this having ever been an E4OD truck. The only evidence of automatic transmission was the C6 kickdown bracket on the IP that came with the truck. This being a 91 purchased from a salvage yard with almost 200k on the clock, I'm pretty sure the IP was a running used one swapped from another vehicle. The pressure line for the clutch is rivited to the firewall behind the engine and I doubt someone would have done that during a swap. Possible, but I doubt it.