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Topic: 2004 era QD7500 Temp Sensor - finiky? (Read 2121 times) previous topic - next topic
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2004 era QD7500 Temp Sensor - finiky?

Yahoo Message Number: 85518
Background

2004 Allure, 31017, with QD7500 with about 465 hours on it.
-In January 2011, we had problems with it starting but then stopping very shortly aftewards. Had the generator dropped out of the rig (no slide on the 04 Allure's), and replaced: belt, temp sensor, water pump, new fluids, oil/filter, air filter, had new Baricade fuel line run too.
-Normal every 4-6 week excercise of rig and generator under load. And a few small trips, with generator usage while on the road.
-May 2012, had the generator serviced fluid flushed, oil/filter, air filter in Sept 2012.
-June 2012, we took a trip and ran the generator with both AC units running for about two hours, running up the Highwary 395. When we reached the stop and go lights in Bishop, CA - the generator shut off. Bishop's temperature was 115 degrees in Bishop. We ran the dash AC until we reached the park we were stopping at in Bishop. After about 45 of sitting, the generator started right up and ran under load for about 20 mins with no problem. The rest of the trip we ran it two or three more times without a problem, until the last day when we running down Highway 101, the generator again shut off. Coach dash temperature indicated low 90's.

Code 33, High Temperature, was the error pulled.

Questions:

Are the Onan QD 7500 Temperature Sensor's just a finiky unreliable product? Dropping the generator to get at the Temp Sensor every few uears, does not sound right to me...

Any other suggestions on items to check?
I was wondering if mounting electric fans to help augment generator air flow while in traffic, especially in hot temp conditions, would help? Not being on a slide is a PITA (Knew this going into the coach, but honestly thought that other then normal maintenance, the diesel generator would be rock solid - surprised to see they are not...

Sorry for the long posting, but wanted to get out as much info as possible... And figured some of you may have been down this path before.

Thanks in advance,
Smitty

04 Allure 31017
04 Allure Sold to a nice new owner! Now enjoying a 07 Magna Rembrandt 45' ISX600 #6775
"We're ONDROAD for THEJRNY!" (Toad and Coach license plates, say Hi if you see us!)

Re: 2004 era QD7500 Temp Sensor - finiky?

Reply #2 –
Yahoo Message Number: 85520
Smitty,

It doesn't matter much but I think you have a QD8000 rather than 7500.
These generators are very slow and difficult to fill the coolant following a flush. I would check that first. Pull the fill port out of the top of the generator and fill slooooooowly.
I never had problems with the QD8000 in my '04 Allure other than the fuel lines which needed to be replaced at about 6 years.

Good luck.

George in Birmingham
'03 Magna 6298
George in Birmingham
2003 Magna 6298

Re: 2004 era QD7500 Temp Sensor - finiky?

Reply #3 –
Yahoo Message Number: 85522
After close to 1000 hours on my variable speed 8000watt genset, the issue turned out to be the radiator. It was found after I threw a magnet on the alternator. Before that time I had issues with the fuel lines and a bad belt for the fan.
TWI 2004 Intrigue 11731

Re: 2004 era QD7500 Temp Sensor - finiky?

Reply #4 –
Yahoo Message Number: 85529
Thanks to you all for your responses.
George - This model year 2004 Allure, was built in Sept of 2003, and it is the QD7500 in this coach. May have change mid year to the 8000?
How often are owners of this generator needing to replace Temperature Sensors? Low hour usage, and this one is about two years old now. Is this a problem item for Onan on this series of generators?
I will doulbe check both of the coolant levels, but as the coach is in for new hoses and belts on the ISL, I had the mechanic also check the fluid levels, and he reports they are both OK.
The temp sensor location on top side of the generator. And the 395 black asphalt heat reflection while sitting at traffic lights in Bishop's at about 115 reported temperatures. Makes me think that the fist shut down was because the unit was simply too hot. No air flow from driving, and under full load of two roof 15K BTU AC's. So that shut down did not bother me too much...
The second shut down at lower temperatures, makes me think I have another Temperature Sensor that is 'too sensitive'... The location is a PITA drop of the generator to get in and replace...
Just wondering what I may be in for over the years ahead... And, suppose if I don't find out anything else is wrong - getting ready to spend more money to replace another Temp Sensor... (Do not want to have it fail for good while on the road, and need to do it someplace where I do not know the costs and skill of the mechanics.:)!
Still wonder if adding a set of electric fans to help augment the cooling while in stop and go, might help?

Best,
Smitty

04 Allure 31017
04 Allure Sold to a nice new owner! Now enjoying a 07 Magna Rembrandt 45' ISX600 #6775
"We're ONDROAD for THEJRNY!" (Toad and Coach license plates, say Hi if you see us!)

Re: 2004 era QD7500 Temp Sensor - finiky?

Reply #5 –
Yahoo Message Number: 85560
So I drove the RV yesterday with generator running and a single AC on for about two hours. The day before that, the shop I had the RV for other maintenance, also ran the generator under moderate load for three hours.
So it is my opinion, that I have a indeed a 'finiky' Temp Sensor. The shutting down in Bishop at 115 degree - I could see as a safe and proper shut down. Not the one coming down 101 South.
A member of RV.Net, Fire Up, shared something that a friend of his has done with his QD, to trick the false shut down of a bad Temp Sensor. (This friend did this as a tempoary work around, I'm thinking of doing it as a permanent option.)
-Retain the existing location for the Temp Sensor, replacing it with a new one.
-Add an AB switch between the normal location Temp Sensor, and add a second Temp Sensor that is in a more accessible location.
Run the unit with the default of "A" being the normal Temp Sensor to the generator ECM. If it starts acting up and error coding 33, change it over to "B" the alternate Temp Sensor location (probably attached to the radiator hose), and see if it allows the ECM to keep the generator running.
After reading many retrieved Google QD Temp Sensor searches, it does sound like the Temp Sensor can be a weak link on this generator. If my generator was on a slide, I would carry a spare Temp Sensor and only deal with it when I needed. With our generator needing to be dropped to access the Temp Sensor, I like the idea of the A/B alternate Temp Sensor switch - to 'possibly' allow us to continue to use the generator while on a trip.
Thanks for the info you all sent, and responses on the board. This may be overkill, but I see it as cheap insurance to not have the generator possibly available on a trip.

Best to all,
Smitty
04 Allure Sold to a nice new owner! Now enjoying a 07 Magna Rembrandt 45' ISX600 #6775
"We're ONDROAD for THEJRNY!" (Toad and Coach license plates, say Hi if you see us!)
 

Re: 2004 era QD7500 Temp Sensor - finiky?

Reply #6 –
Yahoo Message Number: 85564
Smitty

Call the ONAN tech line. I have found them to be knowledgeable and supportive.

Dan 2006 Allure 31348