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Topic: Onan 7.5 Genset (Read 1299 times) previous topic - next topic

Onan 7.5 Genset

My otherwise extensive Foretravel Manual library is missing the operator's manual for the Onan 7.5 Genset. The generator has, on the unit itself, two red switches, one labeled "control" and the other red switch unlabeled except for "on" and "off". There is a glow-plug rocker switch and the "start" rocker. Pre-glow and then activating "start" only results in about a half-revolution, followed by clicking as though low-battery power, but all battery power is well within normal parameters. No start.

Any thoughts or suggestions will be very much appreciated.
1989 Foretravel U300 Grand Villa
Build #3410

Re: Onan 7.5 Genset

Reply #1 –
May have been replaced or upgraded to a diesel. Diesel genset is an expensive upgrade that tends to be more efficient and or  convient. Depending on your perspective. I think 6.5 kw propane was standard. Search internet for manuals and check connections especially the ground.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Onan 7.5 Genset

Reply #2 –
Thank you. Will check all electrical connections.

Onan 7.5 is Diesel, but unknown whether OEM or retro.

Addendum:
Just checked and found that Onan 7.5kw was standard on the 40.
1989 Foretravel U300 Grand Villa
Build #3410

Re: Onan 7.5 Genset

Reply #3 –
Between my last post and going to dryer to throw another load of clothes in it occurred to me 6.5 kw propane to 7.5 kw diesel is NOT a plug and play swap. Wire gauge from the starter to the batteries needs to be evaluated as well as the ground, as the cranking amps on the diesel are going to be much higher than a propane unit. Wire gauge from the genset to the 120 volt panels may also need to be evaluated as well. On the cranking side you can choose to add an additional wires including the ground to bring the amperage up, or run totally new bigger amp wires and take the undersized ones to a recycling center cause copper mines are butt ugly.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Onan 7.5 Genset

Reply #4 –
Quote from: RandallBrink –
Just checked and found that Onan 7.5kw was standard on the 40.
Interesting news indeed, as I thought the early unihome u280 had propane genset based on the beamalarm website.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Onan 7.5 Genset

Reply #5 –
I believe from my research that the U280 did have the LPG, but mine is a U300 4000 with the Onan 7.5 lusted as standard equipment.
1989 Foretravel U300 Grand Villa
Build #3410

Re: Onan 7.5 Genset

Reply #6 –
I see that now, lusted $2-3 k add 7.5 diesel genset appears correct.lol
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Onan 7.5 Genset

Reply #7 –
Diesels are hard on starters. if you have a decompression function try that, but likely you should just pull the starter and take it to a starter/generator(alternator) shop and get it rebuilt or at least checked. Obviously, all electrical connections should be checked, particularly grounds. Try not to start the genset under load and let it warm up before applying load and do the reverse when shutting down. Air and fuel filters are important, carry spares. Coolant should be changed occasionally or checked for acidity.


wantabe

Re: Onan 7.5 Genset

Reply #8 –
I think the 2 switches you are referring too are the remote switches. You should have a control panel on the dash probably and you might have one in the bedroom also. On my 91 I have a gen start switch on my dash where my monitor is and I also have a start switch on my bedroom light switch panel up on my cabinet. Cranking slow and clicking is a sign of dead battery. Check all connections if batteries are good or click in boost switch and see if it will spin.
91 GV U300 Unihome 40' Build 3811
6V92TA Detroit

Re: Onan 7.5 Genset

Reply #9 –
Check voltage at the generator while cranking.  Same at batteries. Let us know what you find.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Onan 7.5 Genset

Reply #10 –
Quote from: RandallBrink –
My otherwise extensive Foretravel Manual library is missing the operator's manual for the Onan 7.5 Genset.

Is it one of the ones in the Media library on the forum?

http://www.foreforums.com/index.php?action=media;sa=album;in=204
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Onan 7.5 Genset

Reply #11 –
It may not be the exact same model, but has the information I need. Thanks very much.
1989 Foretravel U300 Grand Villa
Build #3410

Re: Onan 7.5 Genset

Reply #12 –
@Andy 2 had a separate battery for the genset located in the gen box. His is a 92'. Is yours plumbed into the start batteries or do you have batteries located in the gen box? If so do they what are their voltage.

see ya
ken
The selected media item is not currently available.ken & dori hathaway & Big Agnes
🍺1992 U300 GrandVilla WTBI #4150 FOT FBP 2011
✨6V-92TA DDEC Parlor Coach 350HP Series 92
🏁2011 Nissan XTerra Pro-4X

Re: Onan 7.5 Genset

Reply #13 –
This is of no help but I have a 89 280 and it came with a 7.5 Onan powered by a Kubota Diesel so yours could be factory as well. I don't have a manual either but I get my filters and info from Cummins Onan in Little Rock Ar. I just went there yesterday to get a fuel filter for it.
Dub McBride 1996 270

Re: Onan 7.5 Genset

Reply #14 –
Thanks to all who have provided help with this.

Today, my troubleshooting went a little deeper on the Genset issue. The gen acts like it's not getting enough battery power, and with the two red switches on, it drags the engine batteries down from 14v to 12v (bottom of green batt voltage arc). Turns over once, then solenoid clucks like dead batt.

I am going to remove the batteries and test/recharge to see if there is any indication of old/bad batteries, bad cells, etc.

P.S. Oops--fuel tank <1/4 tank. This could be part of the problem.
1989 Foretravel U300 Grand Villa
Build #3410

Re: Onan 7.5 Genset

Reply #15 –
The generator should be wired to the house batteries, not the engine batteries. That way if the engine batteries are down, you can start the generator and then it will provide a charge so you can start the engine. At least that is how it was originally when it was built.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins
 

Re: Onan 7.5 Genset

Reply #16 –
Then house batteries must be low; will check, recharge, etc. Thanks!
1989 Foretravel U300 Grand Villa
Build #3410