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Foretravel Motorhome Forums => Foretravel Tech Talk => Topic started by: RandallBrink on June 25, 2017, 10:02:00 pm

Title: Onan 7.5 Genset
Post by: RandallBrink on June 25, 2017, 10:02:00 pm
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.
Title: Re: Onan 7.5 Genset
Post by: Old phart phred on June 25, 2017, 10:48:56 pm
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.
Title: Re: Onan 7.5 Genset
Post by: RandallBrink on June 25, 2017, 11:10:07 pm
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.
Title: Re: Onan 7.5 Genset
Post by: Old phart phred on June 25, 2017, 11:32:18 pm
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.
Title: Re: Onan 7.5 Genset
Post by: Old phart phred on June 25, 2017, 11:48:40 pm
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.
Title: Re: Onan 7.5 Genset
Post by: RandallBrink on June 25, 2017, 11:56:12 pm
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.
Title: Re: Onan 7.5 Genset
Post by: Old phart phred on June 26, 2017, 12:45:55 am
I see that now, lusted $2-3 k add 7.5 diesel genset appears correct.lol
Title: Re: Onan 7.5 Genset
Post by: wantabe on June 26, 2017, 05:30:35 am
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
Title: Re: Onan 7.5 Genset
Post by: stump on June 26, 2017, 07:03:00 am
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.
Title: Re: Onan 7.5 Genset
Post by: wolfe10 on June 26, 2017, 09:08:21 am
Check voltage at the generator while cranking.  Same at batteries. Let us know what you find.
Title: Re: Onan 7.5 Genset
Post by: Michelle on June 26, 2017, 11:08:56 am
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
Title: Re: Onan 7.5 Genset
Post by: RandallBrink on June 26, 2017, 12:37:41 pm
It may not be the exact same model, but has the information I need. Thanks very much.
Title: Re: Onan 7.5 Genset
Post by: kenhat on June 26, 2017, 11:58:58 pm
@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
Title: Re: Onan 7.5 Genset
Post by: Dub on June 27, 2017, 12:04:47 pm
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.
Title: Re: Onan 7.5 Genset
Post by: RandallBrink on June 28, 2017, 05:10:19 pm
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.
Title: Re: Onan 7.5 Genset
Post by: red tractor on June 28, 2017, 07:27:57 pm
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.
Title: Re: Onan 7.5 Genset
Post by: RandallBrink on June 28, 2017, 07:46:07 pm
Then house batteries must be low; will check, recharge, etc. Thanks!