LED replacement no flashing

[DREDnot]

GET THAT REVERSE POLARITY BULB GUYS!
It fixes this issue.

 

[NVAM998]

Too strange, I drove the other day and noticed that my brake lights are on unless I press the pedal, in which case they go out. I think I was in service mode. Haven't had time to investigate.

 

[NVAM998]

Yes, either stop or service, now my brake lights are on unless I press the pedal. Confused. Guess adding the troop seats messed up the lights??

 

[Mogman]

Yes, either stop or service, now my brake lights are on unless I press the pedal. Confused. Guess adding the troop seats messed up the lights??

You need to troubleshoot the brake light switch and see if that is the problem, one thing you can do is simply disconnect it, if the lights go out the switch is bad.
Or grossly miss adjusted

 

[NVAM998]

You need to troubleshoot the brake light switch and see if that is the problem, one thing you can do is simply disconnect it, if the lights go out the switch is bad.
Or grossly miss adjusted

Yes, switch is "bad." Multimeter says it is good but it must not be good under load because it won't trip the relay for the brake lights. Odd. Shows <1 ohm with meter. Shorting the inputs to the switch makes the lights come on. I don't have a milli ohm meter and I'm surprised the circuit is that sensitive.

 

[Mogman]

Yes, switch is "bad." Multimeter says it is good but it must not be good under load because it won't trip the relay for the brake lights. Odd. Shows <1 ohm with meter. Shorting the inputs to the switch makes the lights come on. I don't have a milli ohm meter and I'm surprised the circuit is that sensitive.

I am a little confused, I thought you said the lights were on all the time unless you stepped on the brakes?
There is no relay the switch drives the lights directly
Yes the switch can ohm out good but not carry a load.

 

[NVAM998]

I am a little confused, I thought you said the lights were on all the time unless you stepped on the brakes?
There is no relay the switch drives the lights directly
Yes the switch can ohm out good but not carry a load.

Hi,

Yes they were. I tried adjusting the switch, then disconnected it and ohmed it out. Seemed good, but wouldn't work. When I shorted the leads going to the switch the lights work properly and there is an audible click like a relay or flasher type noise. I just looked at the schematic and don't see anything like a relay. Now I'm more confused. Sound seems to be coming from the rear of the truck. Kind of a ping/click type noise when I short the leads. ugh

 

[Mogman]

It does sound like you need a new switch, at least you have a M998 so it is much cheaper and easier to deal with than the 4 speed guys.
I don't know about the click you are hearing, if you have an ammeter you might stick it in the leads and measure the amps going to the brake lights before replacing the switch.
I have heard of folks installing a relay to reduce the load on the brake light switch, was your truck in civy hands before you bought it?
The issue with putting a relay in is if you do not put a diode across the relay coil to kill the reverse EMF the life of the contacts on the switch can be greatly reduced nullifying the advantage of the relay as they are subjected to an arc when the contacts open.

 

[NVAM998]

Interesting. It was with the Guard then a PD and I've been undoing their 12 mess. Maybe they put one in. With my tinnitus it will be fun finding it! It was puzzling for sure as I didn't remember one in the schematic and had to check to verify. And yes a diode in parallel with the coil to clamp the spike when the switch opens up is always a requirement. This is very helpful info. Thanks. Will report back.

 

[Mogman]

Interesting. It was with the Guard then a PD and I've been undoing their 12 mess. Maybe they put one in. With my tinnitus it will be fun finding it! It was puzzling for sure as I didn't remember one in the schematic and had to check to verify. And yes a diode in parallel with the coil to clamp the spike when the switch opens up is always a requirement. This is very helpful info. Thanks. Will report back.

If you cannot find the relay you could put the diode directly across the switch, it certainly would not hurt anything even if there was no relay or if the relay already had a diode.

 

[NVAM998]

OK, so I have a lot on my plate and maybe I'm an idiot. I had installed am XM381 trailer converter for a commercial 12 V trailer connection a while back. That was the relay I was hearing.... Removed the brake light switch and it was pretty rough feeling. Moved it back and forth a lot and drilled two holes into the body and flushed it with Detoxit and kept working it until the carbon stopped coming out the holes and it felt smooth. Didn't drill into the switch itself, just broke through the outer casing. Reinstalled and all is good. New switch on order. BTW, the relay clicking was a great way to adjust the switch position while my head was under the dash.