Generac QP40 generator

hylomatt

hylomatt

Active member
Jan 17, 2022
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Tampa, FL
When I purchased my coach, the original Onan was gone and the owner had a Generac QP40 (QuietPact 40g - gas) installed in its place. No slides involved (boo (n)) but it is mounted on 2 stages of rubber mounts. The whole thing is enclosed and air cooled. I recently had a problem with the battery rectifier/diode turning into a simple conductor and not being able to start the generator. I've pulled it out, done the repair and lots of other testing and cleaning.
The unit draws air into the box, over the engine and through the electric motor, and expels the air with a shaft-mounted fan. I don't really have a good idea of how hot this thing gets while running and after a while of doing so. Something that I wasn't aware of previously is that the "air in" and "air out" cutouts are on the bottom the "air out" is upwind of the "air in". This seems less than optimal for an air cooled engine. Granted, I don't know the temperatures involved but I'm certain that some warmer air is being recirculated.

I wish I still had the power drawer Onan setup because it was much more compact and having a generator on slides seems like a no-brainer of an implementation as well.

Have any of you ever used this particular generator before? How reliable was it? I've just recently started using it while driving and on my last 2.5 hr trip is when it died and the reason for having to pull it out.

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Well... this generator may have bit the dust. I had a heat event and caused some problems. Inside the unit was foam adhered to the panels and 1 big pad of foam came unglued, covered the air intake and after that, I had a melted diode, leaking oil filter adapter and today I just discovered a cracked rotor slip ring. The damn rotor is NLA.

What an absolute PITA.

I'm going to try to find an old alternator repair shop that can repair the rotor or maybe Generac has a different part that supersedes their 0D4484H rotor part.
 
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This is how I planned to solve the generator problem but it can only be used when th coach is settled. This is a Firman3042DF portable generator that runs on gasoline and lpg. The gas comes from an internal tank, so I planned to run it off the coach's lpg tank.
It is very quite being an "inverter generator".
I finally decided to not have a generator at all.
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This is what I finally wound up with but the 2 batteries are being reconditioned in Clearwater by their manufacturer, Lithionics.
If you are interested in the Firman route, you can have one of mine for $500. I am in Palmetto, FL, not very far away from you.
 
hylomatt said:
And so now I'm probably going to belly up to adapting this into my RV
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If I needed a new generator, and I could find one that would fit the space (Jim Bounds mentions that the height of the space is the issue), I would gravitate towards a propane fuel unit over a gasoline unit. I have a propane fueled generator on my Fifthwheel, and I love it. It never varnishes up, and always starts. Plus, I don't have to worry about the fuel going bad. I guess the perfect fit would be a dual-fuel unit that runs on either. The only time propane would be unfavorable would be in extremely low temperatures.
 
I run my generator while driving, for the AC. I just started doing this recently and oh man is it better.

I considered a propane generator and I carry a 62 lb propane tank but to fill the propane I have to move the RV.

I'll probably stick with gas just for the ease of procurement and refills.
 
hylomatt said:
I run my generator while driving, for the AC. I just started doing this recently and oh man is it better.

I considered a propane generator and I carry a 62 lb propane tank but to fill the propane I have to move the RV.

I'll probably stick with gas just for the ease of procurement and refills.
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I have to agree with you on that. Propane while underway is no bueno.

You just convinced me that a dual-fuel genny is the best way to go. I would only run it on gas while driving to keep the fridge and rooftop AC's going. The rest of the time, it would be propane.

As far as the inconvenience of the OEM propane tank, I know others on this forum have ditched their OEM tank and replaced it with 30# bottles.

Now, if only someone made a dual-fuel 6K genny with remote start that would fit our generator compartment, and was quiet.
 
I only have a single rooftop AC but you can run two rooftop ACs on a 4 KW generator. Especially if you install easy starts on each of them.
But yes, 4 to 6 KW dual fuel would be nice. I'd like to have the option to use propane, but I don't want to be limited to just propane.
 
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I really expected more out of generac than this. It makes me a little sick to my stomach that the failure of a $40 part coupled with generac hiding parts spec information and deciding they don't support their RV generators anymore makes the whole thing a pile of junk.

You're just up a creek without a paddle.
 
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hylomatt said:
I run my generator while driving, for the AC. I just started doing this recently and oh man is it better.

I considered a propane generator and I carry a 62 lb propane tank but to fill the propane I have to move the RV.

I'll probably stick with gas just for the ease of procurement and refills.
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I don't need to run a generator for air conditioning. These are (2) 48vdc mini-splits.

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The dash air conditioning has a new 12vdc air conditioning compressor so it provides cold air without the engine running.
 
hylomatt said:
I only have a single rooftop AC but you can run two rooftop ACs on a 4 KW generator. Especially if you install easy starts on each of them.
But yes, 4 to 6 KW dual fuel would be nice. I'd like to have the option to use propane, but I don't want to be limited to just propane.
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FYI, the Onan generators can be converted to dual-fuel. Kelvin Dietz of the Cascaders has done so and can walk you through it. After modification, it is as simple as letting the generator run out of gas (electronically switched cutoff) then switch to propane (the same electronic switch) and restart.
 
hylomatt said:
It makes me a little sick to my stomach that the failure of a $40 part coupled with generac hiding parts spec information and deciding they don't support their RV generators anymore makes the whole thing a pile of junk.
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Know any good machinists? I bet you could fashion a new slip ring and get that thing back in business.
 
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