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Old 07-27-2018, 02:53 PM   #1
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Onan 7500 GenSet doesn't like it over 95 Degrees

Just took a 2300 mile trip with our 2004 Fleetwood Providence. Only issue we encountered was the Genset when we went through Las Vegas when it was in the high 90's and when we were in Elko, Nevada and it also got in the upper 90's. It kept turning off so the rear passengers were suffering. With the road noise and hardly visible Generator light, I didn't know it turned off until they complained. I would just turn on the Genset again and it would run fine between 5-15 minutes. It continued to do that until we reached a cooler area. I was finally able to see the single Blink for Coolant temperature hot code when we were sitting in Elko and the Generator died a couple times so I opened the front and started it up and waited for it to die again to read the code. It would run for hours in cooler temps and we just had it running for 8+ hours the 2 days prior to the trip and it was probably in the low 90's at home wiht out any issues. The only maintenance I performed a couple months prior was the air filter. The Oil and oil filter was done about 10 months ago and we only use the RV about every other month the last year. The only fix I tried was in Elko, I used a water hose and sprayed where the electric Fan was pointing thinking maybe the radiator ( I assume there is a radiator within the unit but it's dark and hard to see.) was dirty and cleaning it would help but it didn't seem to help. It did tend to die less for the next couple hundred miles but that might have been becuase it wasn't as hot. Any other sugestions?
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Old 07-27-2018, 03:24 PM   #2
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Quote:
Originally Posted by gjgross View Post
Just took a 2300 mile trip with our 2004 Fleetwood Providence. Only issue we encountered was the Genset when we went through Las Vegas when it was in the high 90's and when we were in Elko, Nevada and it also got in the upper 90's. It kept turning off so the rear passengers were suffering. With the road noise and hardly visible Generator light, I didn't know it turned off until they complained. I would just turn on the Genset again and it would run fine between 5-15 minutes. It continued to do that until we reached a cooler area. I was finally able to see the single Blink for Coolant temperature hot code when we were sitting in Elko and the Generator died a couple times so I opened the front and started it up and waited for it to die again to read the code. It would run for hours in cooler temps and we just had it running for 8+ hours the 2 days prior to the trip and it was probably in the low 90's at home wiht out any issues. The only maintenance I performed a couple months prior was the air filter. The Oil and oil filter was done about 10 months ago and we only use the RV about every other month the last year. The only fix I tried was in Elko, I used a water hose and sprayed where the electric Fan was pointing thinking maybe the radiator ( I assume there is a radiator within the unit but it's dark and hard to see.) was dirty and cleaning it would help but it didn't seem to help. It did tend to die less for the next couple hundred miles but that might have been becuase it wasn't as hot. Any other sugestions?
Well Sir,
First off, What exactly was the code sequence you were seeing? Second, WHAT ELECTRIC fan are you speaking of? We have an '04 Itasca Horizon 36GD with the C-7 330HP CAT and, the Onan 7.5 QD up front like you but, there is NO electric fan anywhere near it.
Third, cleaning the radiator fins is almost impossible on that coach/generator 'cause the radiator is buried inside the unit. I know 'cause I've had my 7.5 almost completely apart, TWICE.

The primary reason for those 7.5 units to die in hot weather is the temp sensor. Due to its locale inside the cooling system, it gets corroded, even with good anti-freeze in there. When that happens, it now doesn't get the circulation that's needed from the cooled antifreeze and, it throws a fit and tells the little Kubota diesel that It's HOT. When the Engine Ecm sees that, it shuts down the engine.

So, this is why I ask what code you're seeing. It seems there's various codes for different model year Onans, even the 7.5.
Scott
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Old 07-27-2018, 03:39 PM   #3
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2003 Dutch Star on Spartan chassis. The Onan 7.5 would shut down. I wasted time trying the easy suggestions. Finally, I removed the green steel panels so that I could remove the small radiator. I took it to a radiator shop, and they took it appart, boiled the core and "rodded" each tube, cleaned it and put back together. I installed it, and everything was back to normal ( in the sun belt most of the time). Cost was about $50 for them and $200 for me.....
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Old 07-27-2018, 03:43 PM   #4
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It's a single flash on the start button when the engine dies. There are 4 flash codes and descriptions printed on the starting panel and 1 flash reads something like Coolant overheat or engine temp high. I forget the exact wording.
I'm pretty sure there is a fan I saw when looking from the bottom opening on the drivers side and it was at a 45 degree angle pointed torwards the back of the Genset. I put it back in storage so can' go look at it to verify.
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Old 07-27-2018, 03:47 PM   #5
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Originally Posted by Cloud Dancer View Post
2003 Dutch Star on Spartan chassis. The Onan 7.5 would shut down. I wasted time trying the easy suggestions. Finally, I removed the green steel panels so that I could remove the small radiator. I took it to a radiator shop, and they took it appart, boiled the core and "rodded" each tube, cleaned it and put back together. I installed it, and everything was back to normal ( in the sun belt most of the time). Cost was about $50 for them and $200 for me.....
That's something I wouldn't mind doing but I believe I would have to drop my Genset since the Providence doens't have a slide out for the Genset. Maybe I'll do the radiator flush first. -Thanks
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Old 07-27-2018, 03:53 PM   #6
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...yup==make sure coolant is new and full recovery tank; flush radiator system; clean outside of radiator fins; check/change temp sensor; check/replace water pump belt..... challenge is most of this has to be done with top of genset cabinet removed....even more of a challenge for rigs where genset is not accessible on a slide out.....
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Old 07-28-2018, 12:19 AM   #7
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Originally Posted by gjgross View Post
It's a single flash on the start button when the engine dies. There are 4 flash codes and descriptions printed on the starting panel and 1 flash reads something like Coolant overheat or engine temp high. I forget the exact wording.
I'm pretty sure there is a fan I saw when looking from the bottom opening on the drivers side and it was at a 45 degree angle pointed torwards the back of the Genset. I put it back in storage so can' go look at it to verify.
gjgross,
Your coach, or it's generator I should say is, very close to the same era and model as ours. That would sort of lead me to think that, most of its operation and troubleshooting "should" be the same. For ours, in the Onan Service Manual I have it states this:

ENGINE SENSORS
The engine is equipped with a coolant temperature
sensor and low oil pressure cutout switch (Fig
ure
12-2). The associated fault codes are as fol
lows:

No. 2—Low Oil Pressure

No. 23—Oil Pressure Switch Fault

No. 24—Temperature Sender Fault

No. 33—High Engine Temperature Fault
belt can lead to engine overheating.
To remove the belt, remove the negative (-) battery
cable from the battery to prevent accidental starting
of the set during replacement. Remove the 4 bolts
which secure the pump pulley to its hub and pull the
pulley and belt off.
To install a new belt, run the belt over both pulleys
and pull the pump pulley up to its hub and push it on.
Secure the pulley with the 4 bolts and tighten the
bolts according to Thread Torques.
Re-attach negative (-) battery cable to the battery.


So, when you state a "Single" flash indicates an "overheat" condition, I've just not heard of this before. My overheat condition was 3 flashes, followed by 3 more, then a pause, then it started all over again. So, the 3 flashes + 3 more, indicated a code "33" which, as stated, is an over heat condition. But, in other sections of the service manual, there's more potential causes leading to that code 33. Blocked cooling air intake, blocked cooling air exhaust, faulty temp sensor, loose water pump belt, and more.

As for the "fan" you may have seen. Well, it's been a while since I had mine apart but, you may have seen the engine fan. It's a circular one, made of bakelite. It's attached to the magnet section which, is attached to the flywheel. It is very close, if not touching a foam type seal that insures it purchases as much air as possible. You see, that air has at least THREE duties.

1. As it enters the system, it cools the inverter/heat sink, a very large, about 10" x 10" finned aluminum block, right in front, just inside the air intake area.
2. The air is then routed through the radiator fins and, into the second section of the generator.
3. There, it cools the entire exhaust system and is jettisoned out the bottom, towards the rear.

Your water pump and belt is located on the front side of the engine. You will have to remove the top and rear panels to get to them. This is not an easy job for folks that do not have their generator on a slide out tray, such as ours. Even then, there's still a bit of work to get that radiator out.

The temp sensor, which is the most potential cause of "over heat" conditions, is located in the lower half of the thermostat housing, just on top of the engine, right below where the upper radiator hose is attached. Some of those sensors, come out without any issue at all. Some, like ours, fought me for hours. It's about the size of lawn mower spark plug.

Anyway, good luck on your endeavor. Been there, done that, TWICE.
Scott

P.S. Below is a pic of the fan, attached to the magnet section of the flywheel. To the right, is the heat sink, a goldish colored set of fins.
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Old 07-28-2018, 05:19 AM   #8
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Ours did something similar and like others posted it was the coolant temp sensor. Guess we are fortunate ours is on a slide. Getting the top piece off was not too difficult. I did a flush, coolant temp sensor, thermostat, and fan belt along with new coolant. I also was able to rinse the small radiator out which was almost cakes with road dust.
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Old 07-28-2018, 09:57 AM   #9
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Thanks for all the advice and personal experiences. Our next trip isn't planned until September so I have some time to tackle the simple maintenance first before deciding to drop the GenSet to get to the top. Here is a Pic of the panel that shows the Indicator light flashes. I only got the High temp flash. I will update this thread as I make progress.
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Old 07-28-2018, 12:16 PM   #10
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Thanks for all the advice and personal experiences. Our next trip isn't planned until September so I have some time to tackle the simple maintenance first before deciding to drop the GenSet to get to the top. Here is a Pic of the panel that shows the Indicator light flashes. I only got the High temp flash. I will update this thread as I make progress.
Well gooooooollllllllllllllllyyyyyy, as Gomer Pyle would say. I just went out and looked at my control panel for our 7.5 and, guess what, it looks identical to yours only, we don't have the hour meter. I've probably looked at that control panel a hundred times in the 7 years we've owned the coach and, have never paid attention to the actual writing, next to the start/stop switch. So, ya got me there Pal.

But, again, when we had our "overheat" condition, it was the series of 3 + 3 equaling 33. And, if I recall, just prior tearing our gen down, I witnessed the same code on both interior and exterior switches. Hmmmm.
Scott
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Old 07-28-2018, 12:52 PM   #11
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The fan the OP is referring to is most likely part of the coil-condenser for the chassis AC. I’ve seen several Manufacturers install it in that location (to the rear of the generator) with an electric fan attached, Tiffin being one.
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Old 07-29-2018, 12:29 AM   #12
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The fan the OP is referring to is most likely part of the coil-condenser for the chassis AC. Iíve seen several Manufacturers install it in that location (to the rear of the generator) with an electric fan attached, Tiffin being one.
Roger that Sir. I was not aware of that situation.
Scott
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Old 07-29-2018, 09:08 AM   #13
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My Onan Gen Set did the same thing

After 2 months of research and the following, the issue was the fuel pump. We have an Onan 5500.

1) changed both fuel filters
2) changed oil and oil filter
3) filled oil only to lower end of fill line ( to allow for more circulation)
4) removed air damn from bottom
5) changed air filter
6) thoroughly cleaned and degrease the Gen set and squirrel fan.
7) adjusted the altitude valve to my location
8) changed the fuel pump

Hope this helps
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Old 07-29-2018, 10:17 AM   #14
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Thanks for the info Bishop. Did you get the High Temp code also or a different code?
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