Iintermittent complete shutdown related to parking brake/lights

[RickB]

Hey folks,

Need your help on this one:
I was pulling my bus up onto my ramps got to the top of the ramp and engaged the parking brake and everything quit.
It happened once before when I was applying the parking brake as I was parking in the driveway.

After talking to JD at C and J coach here in Minneapolis (second time in a week that he saved me, guy deserves some angels wings...) we came to the conclusion that it was wire # 24 going from a circuit breaker in the front with a number of other wires on it to the back of the bus which is my parking/brake lights. One of the light fixtures was full of water and I was thinking that would have shorted the circuit. Emptied the water, engaged and disengaged the parking brake and she fired right up. The electrician that was working on it with me thinks that the real problem is in the parking brake circuit, he was concerned that water in a light fixture wouldn't create enough heat to blow the circuit breaker repeatedly. He seemed to think that wherever the air sytem of the parking brake interfaces with the electrical system to the brake lights was where he felt the real issue would be.

So, what do you guys think? we are leaving for the black hills tomorrow morning and I am not very reassured at this point. Do you guys feel that a brake light filled with water is enough of a short to repeatedly trip a circuit breaker in the front of the bus, thereby disabling the entire run circuit???

The good news is I can at least drive the bus if it happens again, I will just disconnect the entire brake light circuit and have wifey follow me in the car with her flashers on.

Look forward to your feedback...
Rick

[fe2_o3]

I used to have a similar problem. A fuse would blow when the tail/brake lights were on if the lenses were full of water.
I drilled a small hole in the bottom of each lens to let the water out and the problem went away. I left the holes open and they never filled up again. Hope this helps....Cable 

[NJT 5573]

I think you found the problem. A light full of water will kick a circuit breaker every time. You may need to remove the bulb and give the socket a good chance to dry out. Fire the electrician!

[bobofthenorth]

I'm with NJT - water in a socket can create a dead short and that will trip the breaker every time.  Maybe your electrician is better at plumbing.

[belfert]

Apparently I had debris behind a marker light short out a circuit, so I certainly think water in a light fixture could cause problems.  My marker light didn't look like anything was wrong with it.  I am replacing it with LED anyhow as I already had the parts.

[NJT5047]

I wouldn't think the marker lights or brake light loads would knock off the engine.   Lighting circuits are separately relayed and breakered.   If that situation actually occurs, you might want to look at the dash and FJB wiring...you'll likely find it 'modified'...the breakers should open way before the voltage drops enough to open the engine shutdown solenoid circuit.
I'd think more like a problem ground related to the skinner valve and brake light circuit. 
Those 9 engine room grounds can be pretty nasty.  The next time it quits, see if the skinner valve is shutting off the engine...if so, throw a ordinary battery jumper cable to the skinner valve solenoid and ground it to some good bus engine room chassis steel.    If that works, create some new and improved grounds for your brake lights and skinner valve solenoid.   If the jumper doesn't work, well...the problem is gonna be a little harder to find. 
You may be able to detect a voltage drop at the skinner valve solenoid when the brake lights are applied.  That would indicate a problem with the front connections...likely.  I'd still check all the engine room/brake light grounds.   The jumper cable trick will add a temporary good ground and rule out ground issues. 
Might be a 'run relay' in the RJB that's competing for a ground with the tailights. 
Improving the grounds would be easy. 
I reckon that if something loaded the front buss enough, the engine would shutdown...any load that high should open the offending circuit breaker.  In any event, checking the skinner solenoid voltage will give you some indication of power or ground problems.   I'm not aware of any other items that would shut down the engine...unless you have one of the old Robershaw or similar low oil/water shutdown systems.  If so, defeat them.   Even the low water/oil shutdowns operate thru the skinner valve.
Good luck finding intermittant electrical problems...they are easy to repair, but hard to dx. 
BTW, do you have something like an R&M rear cap with high accessory brake lights on your coach?  If so, those items could add to your problems.
JR