Apparently a new Onan generator is needed - no repair

[kmb1966]

My 2001 Itasca Suncruiser has an Onan Marquis Gold 7000 generator even though it is a 30 amp motorhome, not a 50 amp. Started giving a code 37, brought in to the Onan service center. Service center says debris in the engine, bent rocker arm, burnt valves, some damage to excessive HEAT. Despite all of my religious oil changes, exercising, filter changes and only 750 hours, the unit will cost over 1900 to repair. Can't see spending that much money on that old of a unit. Also, I never understood why the unit came with a Marquis Gold 7000, when a 5500 appears able to do the job. My unit has basement A/C where the 20 amp circuit is tied directly to the 1st compressor (pulls about 12 amps) and the 30 amp circuit is tied to the EMS 30 amp system for the 2nd compressor and the rest of the unit. The Onan 5500 would appear to be able to handle this setup fine, and the Onan 7000 produces more power, but I don't see how I could utilize that extra power with the way it is wired. New Onan 5500 is around $4,000 and a new Onan 7000 is another $1,000
I suppose I am going to go with a new Onan 5500 with new warranty. Onan service center says it can solve the heat problem with a modification to the bin door with a louver/vent and a heat shield. Still trying to get details before I pull the trigger on this deal. Opinions welcome. Thank you in advance.

[STBRetired]

Stim wrote:

msturtz wrote:

STBRetired wrote:
My Onan 5500 will start both my rooftop 13.5K airs at the same time. It does not seem happy about it, but it will start both units. I usually try to avoid that situation.

My QD6000 is an inverter generator. This type has an automatic power protection system that cuts power from the generator if the instantaneous load is too high. This protects the generator from a too high a load and the RV components from voltage sags. A non-inverter generator such as the gasoline models do not have the inverter capability and lack the instantaneous power overload protection. Instead, they rely on a breaker which takes a while to trip which can allow a large drop in voltage and a major load on the generator engine. What actually happens is the speed dramatically drops. Non-inverter generators generally run at 3600 RPM and the frequency of the output is directly tied to the RPM of the generator. the problem of a large load is the voltage sags due to the load and at the same time the RPM of the generator slows down dropping the frequency from 60 HZ to some other frequency. None of these things is good for the generator or the motor running the generator.

The 5500 Marquis is an 1800 RPM generator. When both A/Cs try to start at the same time you can hear that it is working hard but the voltage/frequency don't dip enough to trip out the Progressive Dynamics EMS.

[LVJ58]

kmb1966 wrote:

LVJ58 wrote:
There must be some reason your coach came equipped with a 7000. If it were my coach I would replace it with a 7000 even if it cost more. However it's your call.

Good luck and safe travels....

I spoke with Winnebago today. They called up my serial#. Apparently it was totally the purchaser's decision(the unit was special order from the "ability equipped" division). For some reason the purchaser went with a 30amp coach, but upgraded to the Onan 7000k unit. But with basement a/c, and 30 amp EMS, there really isn't much of a way to utilize the 7,000 over the 5500. Limited to 30 amps. So Winnebago said, just replace with 5500 because the 7,000 would be a waste of $. If it were a 50 amp unit, it would be altogether a different situation.

Well, there's your answer so go for the 5500.

Good luck and safe travels 🙂

[Stim]

msturtz wrote:

STBRetired wrote:
My Onan 5500 will start both my rooftop 13.5K airs at the same time. It does not seem happy about it, but it will start both units. I usually try to avoid that situation.

My QD6000 is an inverter generator. This type has an automatic power protection system that cuts power from the generator if the instantaneous load is too high. This protects the generator from a too high a load and the RV components from voltage sags. A non-inverter generator such as the gasoline models do not have the inverter capability and lack the instantaneous power overload protection. Instead, they rely on a breaker which takes a while to trip which can allow a large drop in voltage and a major load on the generator engine. What actually happens is the speed dramatically drops. Non-inverter generators generally run at 3600 RPM and the frequency of the output is directly tied to the RPM of the generator. the problem of a large load is the voltage sags due to the load and at the same time the RPM of the generator slows down dropping the frequency from 60 HZ to some other frequency. None of these things is good for the generator or the motor running the generator.

[msturtz]

STBRetired wrote:
My Onan 5500 will start both my rooftop 13.5K airs at the same time. It does not seem happy about it, but it will start both units. I usually try to avoid that situation.

My QD6000 is an inverter generator. This type has an automatic power protection system that cuts power from the generator if the instantaneous load is too high. This protects the generator from a too high a load and the RV components from voltage sags. A non-inverter generator such as the gasoline models do not have the inverter capability and lack the instantaneous power overload protection. Instead, they rely on a breaker which takes a while to trip which can allow a large drop in voltage and a major load on the generator engine. What actually happens is the speed dramatically drops. Non-inverter generators generally run at 3600 RPM and the frequency of the output is directly tied to the RPM of the generator. the problem of a large load is the voltage sags due to the load and at the same time the RPM of the generator slows down dropping the frequency from 60 HZ to some other frequency. None of these things is good for the generator or the motor running the generator.

[GREGORYJ]

I believe code 37 is wrong frequency/engine RPM. When my Onan 7000 had this problem, it turned out it was running on only one of the 2 cylinders, the rocker arm was bent (cracked) and so not opening the intake valve at all of one cylinder, that cylinder was cold, the other hot, when running. It was difficult to start with this problem, I had to push the auto choke open it get it started, but it would run and generate power till the load was too high to run at the correct RPM and it would stop with code 37 showing. This occurred with 675 hours on the generator. Replacing the bad rocker and re-aligning the others solved my starting and running problems. I repaired myself and was at most a 2 hour repair as both rocker covers are easy to get at. The replacement rocker and 2 rocker cover gaskets where about $25 from Onan. It appeared the rocker broke because the rocker stud became loose on the cylinder head and rotated out several turns.
Ours is a National Dolphin with basement AC. All gas National RV's with basement AC/heat pumps came with Onan 7000 generators, it was not an option. The basement AC with both compressors running uses 3000 watts. If the Onan 5500 generator had been used, that would leave 2500 watts for other things. If the electric water heater element and microwave were both running (1500 + 1200 watts) that could blow the generator breaker. You would really need to manage your power use with a 5500 watt generator.
We also have never had a heating generator problem with our previous 05 and current 08 National Dolphins with the Onan 7000 generators. We did once have a problem with the generator stopping in hot weather but it was the generator electric fuel pump stopping (seizing) when hot and was easy to replace.
This is just my opinion, but it sounds like your have taken care of your generator and I would be surprised if it really has the problems listed other than the bad rocker arm. And, by the way, others have had a rocker break as well, and even more have had fuel pumps fail.

[kmb1966]

A Good Cigar wrote:
KMB, do you live in an area with very high summer temps? I have an Onan 5500 watt in my 2000 Suncruiser, and being in the Phoenix metro area with zero chance of seeing freezing temperatures, I run straight 30wt oil in it. Several summers with it running during the drive in temps well over 100° and no hiccups. I can't imagine that your 7000 watt has to even break a sweat to power a 30 amp coach! If it was a 50 amp coach it would also have the 7000 watt option, and the same cover and ventilation, so I'd be concerned about the replacement generator having the same problem!
Is code 37 for overheating?

We live in Louisiana. Going thru Texas and Arizona last year, the generator would overheat (or maybe vapor lock) at times. Would run fine after temps were under 95. I do run 30wt oil. I agree with you, and I am too concerned that the new replacement unit will also have the same problem. Onan talks about a heat/shield to direct the heat away from the unit toward the rear. I hope they know what they are doing.
I think code 37 means: See your Onan dealer!

[Stim]

I would get a second opinion on the problem.
Maybe an independent shop.
$1900. seems like new engine price. ???

[A_Good_Cigar]

KMB, do you live in an area with very high summer temps? I have an Onan 5500 watt in my 2000 Suncruiser, and being in the Phoenix metro area with zero chance of seeing freezing temperatures, I run straight 30wt oil in it. Several summers with it running during the drive in temps well over 100° and no hiccups. I can't imagine that your 7000 watt has to even break a sweat to power a 30 amp coach! If it was a 50 amp coach it would also have the 7000 watt option, and the same cover and ventilation, so I'd be concerned about the replacement generator having the same problem!
Is code 37 for overheating?

[kmb1966]

fred42 wrote:
kmb1966,

I have the same 7k unit in a 2007 Allegro. I have no vent in my bin door either. Was there something special about your installation that requires a vent for cooling?

thanks,

Visited with the Onan service center today. They are recommending only a heat deflector at the bottom of the generator to keep the HOT air from sucking back into the cool air intake area. But not recommending a bin door vent or additional fan. There is already a fan on the Onan unit itself apparently.

[kmb1966]

LVJ58 wrote:
There must be some reason your coach came equipped with a 7000. If it were my coach I would replace it with a 7000 even if it cost more. However it's your call.

Good luck and safe travels....

I spoke with Winnebago today. They called up my serial#. Apparently it was totally the purchaser's decision(the unit was special order from the "ability equipped" division). For some reason the purchaser went with a 30amp coach, but upgraded to the Onan 7000k unit. But with basement a/c, and 30 amp EMS, there really isn't much of a way to utilize the 7,000 over the 5500. Limited to 30 amps. So Winnebago said, just replace with 5500 because the 7,000 would be a waste of $. If it were a 50 amp unit, it would be altogether a different situation.

[fred42]

kmb1966,

I have the same 7k unit in a 2007 Allegro. I have no vent in my bin door either. Was there something special about your installation that requires a vent for cooling?

thanks,

[LVJ58]

There must be some reason your coach came equipped with a 7000. If it were my coach I would replace it with a 7000 even if it cost more. However it's your call.

Good luck and safe travels....

[dougrainer]

msturtz wrote:

kmb1966 wrote:

msturtz wrote:

kmb1966 wrote:
My 2001 Itasca Suncruiser has an Onan Marquis Gold 7000 generator. Started giving a code 37, brought in to the Onan service center. Service center says debris in the engine, bent rocker arm, burnt valves, some damage to excessive HEAT. Despite all of my religious oil changes, exercising, filter changes and only 750 hours, the unit will cost over 1900 to repair. Can't see spending that much money on that old of a unit. Also, I never understood why the unit came with a Marquis Gold 7000, when a 5500 appears able to do the job. My unit has basement A/C where the 20 amp circuit is tied directly to the 1st compressor (pulls about 12 amps) and the 30 amp circuit is tied to the EMS 30 amp system for the 2nd compressor and the rest of the unit. The Onan 5500 would appear to be able to handle this setup fine, and the Onan 7000 produces more power, but I don't see how I could utilize that extra power with the way it is wired. New Onan 5500 is around $4,000 and a new Onan 7000 is another $1,000
I suppose I am going to go with a new Onan 5500 with new warranty. Onan service center says it can solve the heat problem with a modification to the bin door with a louver/vent and a heat shield. Still trying to get details before I pull the trigger on this deal. Opinions welcome. Thank you in advance.

I would hazard a guess that you coach is wired for split phase 240 which is 120 per leg to neutral. We have a QD6000 that will not “start” both our 13,000 BTU ACs. The problem isn’t the running load it’s the start load. Starting two ACs even with a hard start capacitor is iffy with any generator less than 7k. Add to that it is very common for there to be other loads such as the converter refrigerator etc. if nothing else is on and I stagger the startup sometimes I can get both ACs running. Most of the time the generator overload protection system dumps all the loads. On one trip I forgot to turn off one AC and AGS started the generator and the first AC started but when the second one tried to start all the power went off from the generator. Bottom line is start loads will strain a generator even if it is able to start them.

Thank you for the feedback. My unit does not have 2 a/c units. It has basement a/c with 2 compressors. First compressor comes on and then if it cannot bring the temp down, the 2nd compressor comes on to assist.

Hmm... I have never heard of such a configuration. If I were to guess each compressor has its own condenser and evaporator by definition would function like two ACs would at least in current draw. The only difference would be the lack of an additional blower motor. A blower motor isn’t much of a draw compared to the compressor motor.

Coleman Basement model. This is the basic model. Pg 13 Figure 11. Doug

http://www.airxcel.com/DesktopModules/RvProduct/Pdf/1976294.pdf

[jplante4]

My Onan 5500 (LP) runs everything just fine in a 50 amp 35 foot coach. If I set the Xantrex inverter/converter to >30 amp input, the start of a battery charge does pull the voltage down to below the EMS cutoff (trying to charge at 130 amps), so I leave the input at 30 amps. This situation is the only one where I thought a higher capacity genny would help.