I have a weird issue with my truck. It is a 2002 F 250, 7.3 4x4. When I press the brakes pedaal the brakes lights come on. When I release the pedal, the brake lights stay on. If I turn the flashers on then off, the lights go off. If I turn my left turn signal on, the left tail light blinks. If I turn my right turn signal on, both tail lights blink.

Here is what I have done so far....
Replaced the multi function switch. No change.
I disconnected the trailer brake controller. No change.
I disconnected the trailer plug at the back of the truck. No change.
I hit the brakes, then disconnected the brake switch at the pedal. Brake lights stayed on.
Ive replaced the hazard relay, with no change.

I am out of ideas.

Steve S.
To many to list.

 

Looking at the wiring diagrams, all signals for stop/turn come though the multifunction switch except the cab mounted stop light.

With the brake switch connected, the cab stop light should go on/off if the switch is good, even if the bed stop lights remain on (because they are controlled through the multi switch). See following diagram of the basic circuit.






If the cab brake light functions properly, the brake pedal switch is good and it leads back to the multi switch or connections to it.

Unfortunately this would mean tracing wires and checking voltages in/out of the multi switch. See following diagram of the switch connections. Pins 8 and 9 are the output for the bed brake/turn lights. As you can see, they are a pass through for the brake switch signal when neither turn or hazard is being used (by way of pin 1).




Obviously this is a tricky problem, but following the diagrams and seeing what is on each pin during failure should lead you in the right direction.



Good luck, Tom

 

I would start at your ground. When I've seen symptoms as such the ground
(corroded or lost altogether) is the culprit.

Good luck.

 

Good point, Xcursion88.

Grounding issues can cause weird problems.

Manually grounding the point inside each of the taillights where the factory grounds connect, will quickly show if this is a possible problem.

If that does not change symptoms, then it's back to checking all connections on the MF switch for correct voltages (0-12V) depending on switch position.

Tom

 

Ok, I got a couple of minutes to look at it last night.

The high mount stop light stays on with the brake lights.

After the brake lights are stuck on, if I hit the brake pedal again, the lights get a little bit brighter, let go of the pedal, and they get a little bit dimmer.

Once the brake lights stay on, if I turn the turn signals on (either direction) the brake lights will go off. It will do this without the key in the ignition (multifuntion switch has no power to the turn signals). When this happens, I do here relays click under the dash (shutting off the brake lights).

Steve S.
To many to list.

 

Steve, After reading this post from you, it seems that what you are seeing is the running tail lights and the brake light on at the same time after the initial press of the brake pedal.

When you press the brake pedal the first time (all lights off), can you hear a relay click under the dash? If so, that is the one most likely latching up that you also hear dropping when moving the turn signal (even with power off). As far as I can tell there should be no relay picking if you do nothing more than press the brake pedal (when the power is off).

The feed to the running tail lights comes through a mess of circuitry that includes various relays and switches.

Did this happen all of a sudden? Could it have been at night.

The reason I ask is because the main switch for the headlamps also includes stuff for the running and courtesy lights.

Try moving the main switch through all positions (then off) and also turning the courtesy lamp switch (rheostat) all the way off, then all the way on, then all the way off again, then test the brake light again.

That switch has been known to cause some strange problems over the years.

Good luck again, Tom

 

Tom,

That is some good things to look at. I did replace my headlight switch recently, due to the fact that the cover was broke. I will put the old one back in.

When the tail lights are stuck on, they are brighter than the running lights, but not as bright as the brake lights, and the high mount stop light is illuminated also.

Yes, I hear relays clicking when the brake pedal is pressed. I can remove the relays that are clicking, and the lights do not turn off.

I am going to start at the headlight switch, then move on to the connector under the hood that goes back to the tail lights, then on to grounds.

Steve S.
To many to list.

 

Ok, I've narrowed it down to the left turn/stop trailer harness. I have pulled the left relay out and my brake light problem has stopped. I will have to investigate that circuit at a later time.

Steve S.
To many to list.