97 Prevost H341 Coach No Crank No electrical power

[mick10]

After a lot of research I finally bought a coach (97 Prevost) to convert from a reputable coach line,  drove it 500 miles home with no issues except the windshield washer pump not working.  I parked it, removed the seats bought all the maintenance items to tune it up but to my dismay one day I went to change the oil and there was absolutely no electrical power-no crank, no lights not even any dashboard lights.  So I left the dashboard master switch on and went out to eat. When I returned all the interior bus lights were on and I started the bus right up no problem.

So every day I would turn the master switch on to be sure I still had power--sometimes start it up and take it for a drive and when I parked it I always turned the dash master switch off.

Now when I turn the dash master switch on there is nothing-the bus is completely dead.

All 4 Batteries show 12.6 each and there is over 24v coming from boost terminals.

Called Prevost PASS they directed me to the main relay and a couple of relays in battery compartment which I purchased and replaced.  Still nothing-completely dead.

Called Prevost again and found it hard to understand the tech as he had a heavy french accent but bought a few more relays-still dead.

The main relay was $400 and I have spent close to $1000 in relays and fuses and yet I feel I am missing an issue that someone with a similar coach may have knowledge.

I have owned the coach for about 3 months and am now a Little anxious that I may have to get it towed in order to get repaired.

I have good mechanical knowledge  when it comes to cars but this has me stumped.  Any ideas or help would be much appreciated.

[windtrader]

It's better to diagnose the problem before buying parts. Diagnose means using an electrical meter to follow the wiring diagram,  probe each electrical junction, and determine specifically where the fault is. It may not even be a part, maybe an intermittent shorting wire. Hope you find the root cause soon and stop spending unneeded monies. Good luck

[thomasinnv]

I would suggest getting hold of a wiring schematic and start checking things out. You're going to remain in the dark if you don't have some kind of schematic to give you something to follow.

Sent from my SM-G930T using Tapatalk

[richard5933]

I don't know much about the working of a Prevost, but I'd say that a universal cause of many issues like this is a faulty ground connect somewhere. Especially if the problem started slow and built to a total failure like this. If those relays are like most, they require a ground connection to function as well.

My first method of attack would be to find every ground connection you can find, and then one by one service them. They should each be disconnected, cleaned (chemically and/or physically as needed), reconnected, and then tightened to the proper torque.

[buswarrior]

Creeping Green Death in the big battery cables?

Cut the heat shrink off those terminals. If they are good, you can goop 'em up to protect them again, same as a car.

But if you find the corrosion...

Happy coaching!
Buswarrior

[mick10]

I am seeing a lot of green even on the relay terminals so I will check the big battery cables as well as all grounds and try to get hold of a good wiring diagram as the one on the Prevost site is too small to read.

I was hoping there was a common weak spot common to this type of bus so at least I could fire her up.

[luvrbus]

Breakers on the bus bars on the H-41 cause you a lot of grief 

[brmax]

I would get the winshield shaded some how then take some steps to electrically check that dash master switch. Following up with these particular wire routings.


Best of luck and have a good day

Floyd

[bandsaw]

Hello, I read your post about your Prevost. I am in the process of converting a 1998 H3-41.  I am curious about where you are located. I am in Oregon and I wondered if you were close. 

As far as your electrical issue,  the biggest battery disconnect solenoid is in the rear side electrical panel.  It is on the back wall above the start batteries.  You could unbolt the cables and move to the other post to by pass it. There is a small switch in the same panel that will disable the solenoid. The switch allows a mechanic to disable the power while he is working on the bus.

Bandsaw

[Jon]

Prevost has excellent and complete information on their web site so don't spend a penny trying to buy electrical diagrams or service manuals. The advice to follow the circuits to diagnose the issue is correct.

If you are looking for a weak point that impacts starting it is the rear start selector switch on the RH side of the rear electrical box, but that may have nothing to do with your problem.

[Geoff]

It has been hinted at in the previous posts, but it sounds like poor battery connections...

[luvrbus]

The H-41 is a unique bus I owned 1 for a while down load the schematics from Prevost ,why they used so many relays in the system is ? to me and the Potter relays are not cheap.A operators manual is a good source of info on a H-41 do you have one ?  

[mick10]

I appreciate all the good suggestions and I am looking for an operators manual.  In a way I am lucky this problem happened while I was at home and not somewhere where I would be stranded.

In addition, it has shown be the complexity of a coach's electrical system and the importance of keeping it in good condition.  So far I have discovered many broken fuses, disconnected wires and lots of green corrosion.

[mick10]

I've made some progress on my electrical issue:

Jumped main relay in battery compartment  and the bus started when I turned the key.  However this only worked once.

 Then while still jumped no start from key but it would start from rear engine compartment--however this worked 3 times then no start rear or front.

Now with main relay still jumped-- I can start bus by jumping starter motor.  This seems to always work.

With one major issue  the red do not shift light stays on and the allison pad is not illuminated. and I can not shift bus.

Any thoughts as this seems very strange.

[luvrbus]

Turn both master cut off switches off and check for power at the transmission,the transmission and engine ECM should still have power with both disconnects off ,the relays are in the rear junction box on a H- 41,you have a grounding problem some where IMO