Alternator failed - problem with fuse box located in shore power enclosure?

[JimNSandy+4]

We have a 2004 Travel Supreme 400 ISL and are experiencing trouble with the Spartan Chassis wiring that connects to the instrument panel and the engine components. The FIRST problem was a sudden loss of 12V to the ignition switch. To resolve this FIRST problem, a separate power line was run to the ignition switch - thusly not finding out what was wrong with this first initial problem. Two weeks later, we were on the road again and suddenly the alternator failed (the tech has just now replaced the alternator) and now the tech has traced the problem back to the fuse box located in the shore power enclosure (near the rear left side of the coach). I need help in trouble shooting this area - so any wiring diagrams or suggestions would be very helpful.
Jim Uhl, Albuquerque

[jDavid]

Sounds like you have a loose connection or a power contactor that is intermittent. I have had a problem kind of like yours. It took a lot of troubleshooting and phone calls to the chassis manufacturer before I finally figured it out. My was a combination of things, two loose connections, one defective alternator (confirmed bad at a alternator shop with me watching) and one defective Si-80 contactor. Actually at the end, I had 4 Digital volt meters taped to the windshield, a portable oscope and a couple other tools monitoring the coach electrics. I just kept turning things on and off while recording the findings ( I use to be a flight test engineer). It was kind of fun in a weird way. I am glad it is fixed though. The coach would shut down anywhere and time before I finally fixed it. Good luck!

[JimNSandy+4]

Thank you for responding. We'll pass your experience/knowledge on to the 'tech' at Cummins Rocky Mountain here in Albquerque and hope he can find the correct solution.

[EngineerMike]

Some pusher coaches have a main 12V breaker in line between the battery/starter/alternator and the ignition up front that starts to fail intermittently, then fails udderly (it has a cow, then dies).
If yours has one, a) you should carry a spare, and b) check the resistance across it (should be verry close to zero) and the voltage across it (should be flat zero). If it has resistance or voltage difference, replace it.
Yours may not have such a critter.

[JimNSandy+4]

Thank you Engineer Mike also for responding. We'll also keep your suggestion in mind when we go see the "tech" again at Cummins tomorrow.

[jDavid]

Any headway with finding your problem? I just looked at my Spartan drawings for out 95 eagle with a mountain master chassis. 12vdc is feed from a junction box up front. My chassis has a "master relay" which feeds a group of switched and unswitched circuits. The unswitched circuits receives 12vdc from the input side of the master relay (12vdc from the chassis batts). A wire (#133) feeds the input side of the ignition switch. From the switched output of the ignition switch, 12vdc is applied to the high side of the master relay coil which energizes the coil and applies 12vdc to the switched circuits which include the engine fuel shut off relay.
I hope this helps. I really believe that if you look closely at the relay feeders, you will find your problem. But of course I could be wrong. In any case call Spartan and they will email you or snail mail you a copy of these circuits. My 95 could be completely different from your coach.

[JimNSandy+4]

We had an excellent response from Spartan Chassis who was very customer oriented - what a refreshing experience!! They provided the schematics of the electrical system in a pdf format and also suggested the area that needed to be fault analyzed. The most likely cause of the problem was the rear Bussman relay fuse box. This part is now on order and the faulty part will be inspected and repaired as a spare. We'll let you know if anything different happens that would affect this solution.

[jDavid]

Yep, I had the same experience when I contacted them. Extremely helpful and went out of their way to help me out.

[JimNSandy+4]

Well, folks. This is turning into a desperate tragedy. The technician mis-diagnosed the need for the Bussman fuse box ($300+). We received the new box and put it in (it is a bear to install, so it's staying there) and found that there is still the same problem. The fuse box did not fix anything; there is nothing wrong with our old fuse box. We have looked at the schematics and traced a wire that goes to SPL2 (assume that's a splice???) Now we have a call into Spartan to find out where that goes. If they do not know, any suggestions on who would know - how would we find out? Appreciate feedback.

[jDavid]

You are going down the same road that I went. Careful, you will spend a lot of cash and still have the problem.
Disconnect all of your power sources (batteries, shore power, everything). Start at the front of the coach and start physically checking every junction box for loose connections. Specifically the main power solenoids under the hood.
You should have a junction panel up front, one close to the battery compartments and one where ground power comes into the coach.
If you have a voltmeter, when everything is connected, find the accessory solenoid relay (there should be two, side by side). I suspect that to be where your problem is. A Tech at American Coach told me that they are typically the problem when you have a intermittent like the one you are having. I did not believe her at first. I do now. Good Luck, Good Day!