trying to trouble shoot non working braking lights. no 12v. to either lites or toad plug. with air brakes where would I find brake lite switch? Also, wouldn't switch be on the ground side of circuit? to trouble shoot, shouldn't I find 12v at lite if I were to ground one of the supply wires? my system also has braking circuit separate from turn signals. thanks for any input especially on where the brake lite switch should be located.

Hey Bob, the brake light switches are usually located on the air foot peddle accuator. There should be 2 of them.

I Recently had the same problem and found the connections on the switches were very loose. Tightened them up and the trouble went away. I do have a Spartan chassis though so there may be some differences.

I'm assuming the front two larger switches would be brake lites as air lines go directly to treadle valve. Are they switching the ground or 12 v side? Why 2 switches? thanks

Probably 2 swiches for redundancy. Those 2 switches should be the ones I am talking about. Looking at those terminals thety look BAD, clean then real good and see if that corrects the problem

I think I see the problem - it looks like your supply wire, circled in red, is corroded. It might even light up your test light without a load on it.



the slight bump and discoloration you see, circled in red, looks like the wire is probably rotted away in there.

Check it with brake pedal depressed. It might still have power but then looses it when under a brake application condition.

When you move the wires to clean it up it may start making contact again. Move the wire at the spot to see if it feels different inside of the plastic.

I was more concerned about all that green scuz on the right switch back terminal. The switches are in parallel so if any terminal that has three wires connected to it had a bad connection or corroded wire, it would effect the entire brake light system.

When mine went bad, the cruise control would not shut down, a bit scarry, had to switch it off manually.

Your elctrical schematic in the coach has numbers for each wire. in my Gillig manual there is a schematic with each wire identified. The number on the wire looks like it says 10a-14. You can determine where it connects and whether it is power or ground.

I know it might sound like I have stock in NAPA, but if you need the switch you should try there.



Part Number: MBI BE13250
Product Line: Midland Brake Products

Brake Light Switch

Well brake lites are up and working as they should. 12v. supply wire was corroded about 3 inches from connection as pointed out to me from pic. Fixed the corroded wire (looked as if someone had proded it with a test lite at that point)Cleaned up all connection points on brake switches. Applied brake and tested for 12v on both switches...nothing except for supply side. BOTH switches were shot. Replaced with 2 new ones. Now all is as it should be. Thanks guys for the excellent help.

Eagle eye Bill! Good call, looks like somebody had poked it with a test light.

You'll notice that a lot of times we'll ask "Got pics?" This is because we like to look at what you have and it makes it easier to diagnose on our end.

You might ask... how did you know, in that gaggle of wires, what was power supply and what was feed at the brake light switch?

Power supply wires, after awhile, will tend to have a green tint to it. To combat this, you should spray the connection with a battery protector spray.

I would like to see the repair that you made to the brake light switch. Did you splice it? did you butt connect it? Was heat shrink tubing used? Did you just cut it down and install a ring connector? How far up the wire did you go?

The correct answer should be: I cut the wire back until I no longer saw the green (could also be powder white or rust red) corrosion in the wires. Because I had enough room, I placed a ring connector on the end of the wire and installed it. I then sprayed it down with battery spray protector.

Now, if I was doing this job and I used the same type of switch, I would also use the center connection for the power supply wire. Why??? It's farther away from the ground case of the switch and if the power did leech out, it wouldn't corrode as bad.

Here's a tutorial I did a few years ago... Failed wiring and how to protect against it. FYI...

As always great advice Bill!

Bob, I would like to add if you are experiencing a slow air leak, check the small air switches located just behind the ones you replaced. I searched and searched for my air leak and found these switches were leaking. I still have a slow leak on the rear air system and think it is from the park brake valve.

At least your switches are in a very accessible spot. My brake light switches as mentioned are on the foot valve and almost inaccessible.

corroded wire would have been too short if new ring connector had been attached at bad point in wire...used a butt connector and shrink tube...no bat spray as of yet. New brake switches had a different terminal configuration than oem with both terminals equal distance from case. New switches came from truck part supplier as our napa didn't list them. Just got home from 4 days of mh use and all is well.

I do not know if you have relays but if you do, it could be tha one that is for the lights in the back
lenny
PS bill knows if you would have one(HE KNOWS ALL)CLUB TRAKER
SHINSEI