Help with Brake Light Issues

[gary_curtis]

I took a look under the Brake pedal and did not find any type of electrical switches.  I expected to find a GM style brake switch instead I found something that did not look serviceable at least by me (see photo brake pedal)

Then I extended the generator and took a look along the firewall. I found some sensors but they appear to be connected to air or hydraulic lines so I am not so sure I want to tear into that system. Better left to someone like Ohio Cat. (see photo of brake switch)

Looking at dwg#38070227 there appears to be two circles in the upper right corner that could be the brake switches in the photo.

If I short the two terminals on one of the circles will I get a brake light?

[Steve Huber Co-Admin]

ary,
My error. Sorry. I was thinking of a different coach.
Before shorting anything together, I'd do the following;
 -Verify there is a 12v supply. Either check at the 15A brake light fuse shown on the drawing or verify that there is 12v at pin 30 of the Engine Brake Light relay (R87).
 -Verify that the switches you IDed are the brake light switch(es). The dwg shows a gray wire on one side of the switches and a Blk/Wht on the other side. The picture seems to show gray wires on both sides. Suggest pulling one wire from the switches and verify continuity across the switch when brake pedal is depressed. I'd also use an ohm meter to verify a connection between TS1-5 and one side  of the switches to confirm continuity and that they are the right ones.
Steve

[gary_curtis]

I did some research and I am 99% sure that the two round sensors are the brake switch (See Halidex BE13250 brake switch).

The lower sensors look like low pressure sensors in an RV Catalog (see Nason Low Pressure Sensor).

[gary_curtis]

I probed around a bit to see if I could get a brake light signal (on Terminal 5 of TS-1) from the relay that is above the DRL headlight circuit. 
The relay in schematic notation is FRB 16-K4.

While reading through the 2007 electric diagrams I came across this relay in Dwg 38060870 so I guess the relay is driven by the air brake stop light switch and also supplies the brake signal to the proportional brake controller.

There is continuity to ground at (16-J4-4), Continuity and 12.5V at (16-J4-1) and continuity to Terminal 5 of TS-1 from (16-J4-3).

I should have gotten a signal from the brake light switch (J1-17) at (16-J4-5) but I didn't. 

There was 12.5 volts at the air brake light switch on one of the terminals so I shorted the two terminals together but unfortunately I did not see any brakes lights...

I did not short the second air brake switch so maybe both have to be shorted to work...somehow the brake signals switch from 2 wires to one and I have not found that yet in the diagrams.

I also found an inconsistency in the wiring diagrams. The Brake controller diagram calls out J1-17 as driving pin 85 of the relay and on the Hamsar wiring module they are calling out J1-12. This may be a loop that goes from the brake light fuse through J1-pin 12 and returns on J1 pin 17 if the brake switch is closed.  I have to check that out.

[gary_curtis]

SUCCESS!!!!!!!!!!

I have brake lights! I went to the local auto parts store (NAPA) and purchased some alligator clips on 30 inch leads and a 5 pin, 40 amp relay.

Back at the coach I shorted the brake switch posts with the alligator clips since I was working alone and I did not have anyone to pump the brakes. I measured 12.5 volts at pin 85 on the relay but still no lights.....

I removed the DLR Module from the Board 16-K4 location and inserted the new 5 pin 40 amp relay.  I had brake lights!!!!

So it appears that I never had working brake lights.  When the salesman did the walk around with me last Feb, he had the hazzard lights on which also flashes the brakes and center brakelight.

It is difficult to troubleshoot something when you have the wrong parts installed.

I appreciate all the help and encouragement I received from this site. Glad that I am a member.

[Steve Huber Co-Admin]

Gary,
Glad you've got brake lights! But.... since K4 is used for both the hazard and brake lights and your hazard lights worked, K4 had to be functional. My guess if that there is/was something else on the DLR module, probably an open connection that made contact due to your removal and reinstall, that was/is the culprit. It almost has to be a connection that feeds pin 86 of K4 from TS1. The overheated wires and connector on the DLR module as well as the traces from the connector to K4-86 would be the chief suspects. In any case, if it happens again, you'll know where to look.
Steve