Community Forums

diveman · 07-04-2015, 05:54 PM

Hi All,
This is my first time posting on this site. I've searched the forums to see if anyone has had the same problem with there generator, but haven't found any information.
Here's What it is doing, Nothing! It started right up a couple of weeks with everything working as it should. It charged the batteries right up, ran great, just like it should. 2 days ago I went to crank it and nothing, not even the red light on the remote switch or the gen set itself. Now I'm scratching my head trying to figure out what happened.
We had just crossed over the top of the world highway, rough, dusty bumpy, maybe a loose connection. So I checked the electrical plugs and fuses under radiator cap, all good. 12 volts going through all the fuses.
Here's what all I've checked;
Checked voltage at positive and negative cable on back side of gen set.
Cleaned cable ends and lugs out side of gen set, not the inside as I can't get to those without pulling the sound shields off.
Pulled the front cover of gen set to get to wiring and voltage controller, everything seems to be tight.
Checked the start/stop switch, it changes voltage as I think it should as it energizes the fuel pump and glow plugs when its pressed.
I put a battery booster on the back pos/neg cables thinking maybe I had voltage but low amps, still nothing.
My thoughts are still a loose cable or connection, and I'm hoping its not the control module, but I can't imagine that going bad as it wasn't running and ran fine till the moment I shut it down 2 weeks before.
If anyone has any suggestions or knows what the problem is, it would be of great help. the only connections I haven't checked are the low oil, coolant over heat and th pos/ neg cables inside the box.
Thanks in advance,
Diveman

Ryan7361 · 07-04-2015, 06:08 PM

Is it trying to turn over? (is the starter turning?)
If it is trying, check to make sure your getting fuel to it. Try to start it a few times and then quickly pull the fuel line off(diesel should be flowing). That might help you narrow things down.

diveman · 07-04-2015, 11:26 PM

nothing, no clicking, no fuel pump. I want to think it' in one of the connections inside, but I can't tear it down any further than I did yesterday while in this park. I don't think it's the inverter controller bad because I get power coming out of the switch, but nothing happens.

FIRE UP · 07-04-2015, 11:32 PM

diveman,
You've given a great description of what's happened and, how you've gone about diagnosing it. You don't say what kind of coach it's in, not that it matters all that much in this issue. I only mention it because, there are many coaches out there that have those 7.5 units on a slide so, it can come out the front for easy service and, diagnosis of problems.

If yours does not slide out, it will be difficult to get the paneling off so you can get to the starter. I mention getting to the starter to see if short circuiting it at the terminals would turn it over.

If your glow plugs are doing their job which, it sounds as if they are due to your analysis of the voltage drops during testing procedures, then it sounds as if the engine ECM is doing its job. And, that goes for the temp sensor too which, is the culprit for many-a problems of the 7.5 units. At this point, all you next is try and get to the battery connections at the back of the Gen to see if they're clean and tight.

One more thing, make sure your cables on the batteries are in great shape too as some of them, lead right to the gen.
Scott

diveman · 07-05-2015, 09:23 PM

It's a 2000 Newmar Mountain-Aire and yes it is on a pull out tray on the front. So today I pulled the top and drivers side sound shields of to get to the starter and engine wiring. Cleaned all connectors and ground straps. Checked for 12 volts at starter and traced my hot wire to the start switch. I have power leaving the start switch going to the control/inverter but I cannot see that it's coming out to the glow plugs and fuel pump. It's gone above my pay grade, tomorrow it's going to cummins, hopefully they will have something to test the control/inverter with. I'll let you know what they find.
Thanks for the reply,
Larry

FIRE UP · 07-06-2015, 11:16 AM

Quote:

Originally Posted by diveman

It's a 2000 Newmar Mountain-Aire and yes it is on a pull out tray on the front. So today I pulled the top and drivers side sound shields of to get to the starter and engine wiring. Cleaned all connectors and ground straps. Checked for 12 volts at starter and traced my hot wire to the start switch. I have power leaving the start switch going to the control/inverter but I cannot see that it's coming out to the glow plugs and fuel pump. It's gone above my pay grade, tomorrow it's going to cummins, hopefully they will have something to test the control/inverter with. I'll let you know what they find.
Thanks for the reply,
Larry

Larry,
Thanks for getting back to us on this and, what you've done so far. I think you're really close to finding the problem. It can be frustrating to say the least. It will be interesting to see what Cummins says was/is the problem. Please post here so that we all may learn.
Scott

diveman · 07-06-2015, 11:06 PM

Scott,
No problem, It just aggravates me when I can't fix something myself. This morning I drove over to Northwest Cummins in Fairbanks, AK. Well they don't have a Onan repairman there, He comes from Anchorage on Thursday. But the lady in the office was really helpful, gave me phone # and names of people to talk to there. Now I know I said I was done messy with this thing, but you know what happens when you got to much time on your hands, and 'your mind goes to wondering. SOOO! today I opened up the hood , rolled out the genny and started another day of checking. Pulled the front cover off ,labeled all the wires that weren't number matched and pulled the hole control/inverter out to look inside. pulled the top cover off the board to examine, checked any connectors, made sure everything was tight. looked everywhere I could for burn marks, hot spots, scorched varnish, anything out of the ordinary. every thing looked like new. I kind of wish I would have found something, anything that would make me think its the board. Which it very well could still be. Who Knows
Thursday the Onan rep will be here to test/ diagnose it I hope. It's $190.00 for him to check it and tell me what's wrong with it. Can't wait! If I'd known they were going to charge that much I would have left it together, but maybe he'll cut me some slack. The new control/ inverter from Cummins $2300.00 Plus freight. That's a hard one to swallow.
I'll let you know as soon as I find out what it is.
Larry

diveman · 07-10-2015, 10:13 PM

UPDATE! UPDATE!
I have a working gen set now. it was the control/inverter. Everything pointed to that, but I was in denial. took it to Cummins and had them check it as well before spending $2300.00 for the inverter. he confirmed it was the board. I ordered a new one it came in today, got it installed and it runs like new. Thanks for all the help.
Larry (Diveman)

TQ60 · 07-11-2015, 09:34 AM

Check with manufacturer as a field replaceable part that expensive may be something that can be repaired.

Ask about exchange as sometimes they do that too.

May be too late for yours but the old one still may be repairable or exchanged for a spare.

Or you may get credit...does not hurt to ask!