AC and Starting Problem

[Roger Rempe]

Recently, I've been experiencing a sporadic problem with turning on the ignition and nothing happening. No dash lights and no engine turning over. Generally, second or third attempts were successful. Dropped off the MH this a.m. at a Denver Cat service center and it died on me in the lot as I turned on the dash air conditioner while it was in drive mode. We've not driven it with the AC on since purchasing it a year ago and having the same thing happen. It doesn't die when it's in neutral and I turn on the AC. I figured that since I was in a Cat SS and safe that I'd give it a go and maybe they could check that out too. It wouldn't start and I thought that this is a good thing since I got it there without needing a tow and there was the problem in their lap. Just got a call from the tech informing me that he had no trouble starting it and after two hours of testing things he couldn't find any abnormalities...sheeesh! We decided to replace the ignition solenoid anyway. They're gonna keep it overnight and see if it starts okay in the a.m.
I was told by the service rep that Cat doesn't work on electrical issues which surprised me. That being the case,  can anyone recommend an outfit that can fix my problem or come up with a solution? We've had numerous other electrical issues in the past year since buying this Monterey and have mostly come up empty for fixes. We are full timers and are trying to work our way to Illinois for the near future.

[Gerald Farris]

Roger,
There is probably a 90% chance that all that was wrong with your coach was a defective $25 ignition solenoid. You description was a classic ignition solenoid failure.

Gerald

[Roger Rempe]

Would that also take care of the stalling when I turn on the AC Gerald?

[LaMonte Monnell]

what is your idle speed set at Roger? Low idle in neutral may keep the engine running, but shuts down in gear when turning a/c on due to low rpm's possibly! Just a guess though, I sure am no expert by any means!

[Gerald Farris]

Roger,
I can not be sure if the problem of your engine dying when your dash A/C is turned on is related to a defective ignition solenoid without checking several things like compressor drag and idle speed, but there is a good chance that a new ignition solenoid will correct that also.

Gerald

[Roger Rempe]

Thanks guys! I will mention that to the tech this a.m. when I pick it up. Wish me luck...I've got three hundred miles to drive today in "tornado alley"! 
Roger

[Roger Rempe]

Well, after leaving the Cat service center and driving about 60 miles we pulled over at a truck stop for fuel. Went to start the MH and nothing...no dash lights either. Fortunately, a diesel truck repair shop across the street came to the rescue and was able to jumper across the new ignition solenoid so that I could drive it over to their shop. They replaced the new solenoid with another. The mechanic noticed the diode jumper on the bad solenoid and mentioned that he'd never seen that set up before. Went ahead and reattached it to the newer one. Tried to start the engine and nothing. So, he removed the diode and everything worked fine. We were able to complete the rest of our journey. Also, one thing that I noticed after pulling into our site was that the solenoid felt somewhat hot. Is that normal and what's the deal with the diode jumper?
Special thanks to you Gerald for taking my call yesterday and your sage advice in this matter!
Roger

[Gerald Farris]

Roger,
If the diode failed (shorted) or if it was connected in reverse direction, that would cause your problem but the diode would get hot and even start smoking in a short period of time. The diode is installed across the trigger wires for the ignition solenoid to prevent the minimal current back spike that can be created in the solenoid windings as the ignition is turned off. I always reinstall the diode when I replace an ignition solenoid, but I have seen several coaches that have run for years minus the diode without a problem. It is a solution for a problem that could theoretically exist.

All solenoids get warm when they are continually engaged. That is the reason that you only use continuous duty solenoids for the ignition solenoid that are rated for at least 85 amps. An intermittent duty solenoid will fail from overheated windings if used in a continuous duty application.   

Gerald
   

[Roger Rempe]

That makes sense to me Gerald. So, that's why nothing worked until the tech removed that faulty diode. I obtained a small alligator clipped jumper from the tech just in case I get stranded again!
A bonus from all this is now my dash fuel gauge appears to be working for the first time since buying the rig...coincidence?  Last summer I had paid Beaver Sales & Service to fix that by replacing the the sending unit (their idea) and discovered after driving away that it still was stuck on full.
Electricity sure is a funny thing! 
Roger 

[LaMonte Monnell]

I agree Roger that electricity is a funny thing, not funny as haha funny but weird funny!

When working on fighter jets most of my life I always had an electrical expert close by for those funny troubleshooting moments!