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RVing message boards => Tech Talk => Topic started by: Wagonmaster2 on January 16, 2014, 02:49:42 PM

Title: Onan 7.5 diesel generator air filter change
Post by: Wagonmaster2 on January 16, 2014, 02:49:42 PM
According to my owners manual on the 7.5 Diesel Onan generator the air filter is supposed to be changed every 500 hours, or once a year.  I've been blowing mine our with air pressure (from inside towards outwards) every year and replacing it every 3years years with about 150 hours each time.   Now with just under 500 hours and 10 years old I'm thinking about replacing it again.   It has never been very dirty whether blowing out or replacing, but just wondering how many of you actually replace your air filter every year.

Also, can the engine V-belt be checked very good from underneath without actually removing it?  And the manual says to replace it every 5 years or 1000 hours, is this really necessary.   My 1991 Honda manual said to replace the engine drive belt every 6 years or 90,000 miles but mine was changed at 73,000 miles after over 15 years and the mechanic had a hard time finding a crack in the old one to show me.
Title: Re: Onan 7.5 diesel generator air filter change
Post by: Gary RV_Wizard on January 16, 2014, 03:56:09 PM
Like you, I stopped replacing it annually because it is rarely even a little dirty. However, every year I pull it an inspect, and blow out if indicated.

Given the location of the air intake, it wouldn't take much run time on a dusty road or campsite to load it up, though.
Title: Re: Onan 7.5 diesel generator air filter change
Post by: Old Snipe on January 16, 2014, 06:16:04 PM
I have the sister MH to yours, the Winnebago Journey.  The generator belt cannot be checked from underneath, the generator has to come out.  I did a blog post with picture on what was involved.  You can read about it here:

http://rsanityrvtravels.blogspot.com/2013/04/onan-generator-service.html

My belt had about 1850 hours on it and while it looked ok, it did have glazing on it.  Because the belt drives the water pump, I was glad to replace it before the glazing caused slippage, which could have led to the generator overheating.

Based on my experience, I think I would go 1500 hours before I change the belt again.  I had it done at a Cummins Coach Care facility in Columbia, SC.  It took two days and cost around $1000.  I had the generator oil, filter, fuel filter and air filter changed at the same time.

Best Regards!
Title: Re: Onan 7.5 diesel generator air filter change
Post by: Wagonmaster2 on January 16, 2014, 09:15:58 PM
Wow, $1,500 to change a fan belt.   And I got took by a Freightliner shop when they charged me for 20 hours labor to change the fan hub bearing on the Meridian.   Gaffney tech that answered the phone when I questioned that much time was really surprised and he said he had done it many times in one day.  Oh well, as all these shops know, all us RVers have money running out our ears.   Don't I wish.
Title: Re: Onan 7.5 diesel generator air filter change
Post by: Mavarick on January 17, 2014, 01:17:45 AM
I also donít change my air filter yearly as I donít do much dry camping. With our AK trip as an exception I think my genset gets more maint. run time then running because I need it. Ours only has about 400 hrs on it so the belt isnít getting changed either. If it was a critical part, such as the timing belt in a car I was driving, then it would be a different story. As it is, if the genset belt starts to go chances are it will happen when Iím doing my monthly run in!
Title: Re: Onan 7.5 diesel generator air filter change
Post by: Terry A. Brewer on January 17, 2014, 03:24:09 PM
>>As it is, if the genset belt starts to go chances are it will happen when Iím doing my monthly run in! <<

No...When that belt breaks you will be out in the middle of nowhere on a Sat,Sun or holiday.  No belt no generator.
Title: Re: Onan 7.5 diesel generator air filter change
Post by: Mavarick on January 17, 2014, 07:24:04 PM
Terry, I would normally agree with you but you didn't read my post very close. IF I was in the middle of nowhere the genset would become a critical part. It is not critical however in the middle of a KOA!  ;)
Title: Re: Onan 7.5 diesel generator air filter change
Post by: Gary RV_Wizard on January 17, 2014, 07:45:02 PM
I checked my belt at about 1400 hours and it looked fine. I have just shy of 1900 hours now, so probably pushing my luck. I can get at the back of mine by pulling out the slide, then crawling in behind and removing the genset covers, but its still a major chore. Probably a 3 hour job on mine.
Title: Re: Onan 7.5 diesel generator air filter change
Post by: Wagonmaster2 on January 18, 2014, 09:02:23 PM
If the belt runs the water pump what will happen when (or if) the belt would break while the generator was running (probably wouldn't break if the engine wasn't running would it)?   Will the gen really overheat and lock up or is there something that will shut the engine down when the coolant reaches a high point (or am I just dreaming)?

I think I've read there's a low oil shut off but nothing about overheating.
Title: Re: Onan 7.5 diesel generator air filter change
Post by: Mavarick on January 18, 2014, 11:03:22 PM
You should have a coolant temp sensor that will shut you down in an overheat condition. Your controller will blink once for high temp and that will give you a fault code #33, high engine temp. if you go into your codes (check your manual for the sequence). The coolant temp sensor is in the thermostat housing. If you decide to change the belt use genuine Onan not aftermarket as there is no adjustment so correct belt size is crucial. Yes, there is also a low oil pressure cutoff switch, same side of engine about halfway down on the side of the block and you will get 2 blinks for low oil pressure shutdown. Let me know if you need a service manual for it.
Title: Re: Onan 7.5 diesel generator air filter change
Post by: WILDEBILL308 on January 19, 2014, 12:23:31 PM
I changed mine the first year because I had no seversice records. I did every thing except the belt the first year but I will only look at it this year. I have not used it much. I am changing the oil and filter.
Bill
Title: Re: Onan 7.5 diesel generator air filter change
Post by: Wagonmaster2 on January 20, 2014, 07:20:28 PM
Thanks for the offer Mavarick, but since my gen has to be dropped out the bottom for any service other than fluid/filter changes I doubt a service manual would help me that much.

You mentioned the  controller would blink, what or where does this have reference to?  Is this on the dash?
Title: Re: Onan 7.5 diesel generator air filter change
Post by: Mavarick on January 20, 2014, 07:41:50 PM
Wild, that is exactly what I would do also. I just figure part of the cost of buying used is performing service on everything unless I can prove something has been done. Most of these components are way too expensive to hope that someone performed the service before I bought it.

Wagon, sorry, the controller is what controls the status light on the switch and that is what you will see. (The small LED light on the switch you push to start the genset.) When cranking it will blink constantly, when running it will stay lit and when a shutdown occurs it will blink in reference to fault codes (for the first 5 minutes anyway). You have first and second level fault codes and that is what I was saying to check your manual for. I can send you an operator manual (I think) if you tell me your model, or the service manual if you like reading.
If you have a shutdown your switch will blink, either once for high temp (blink, pause, blink, pause, etc) or 2 blinks for oil pressure (blink blink pause, blink blink pause, etc) or 3 blinks for something else, (you get the idea.). If you hit the stop side of the switch you will then activate the 2nd level codes which will give you the details so to speak. For example a high temp shutdown would blink once at first level, then when you hit the stop side of the start switch it would change to the 2nd level codes and you would get a # 33 code for high engine temp (blink blink blink pause, blink blink blink pause, and then reapeat). That is a simple example and the manual will show you a lot more codes that could shut you down if a problem comes up, I only use this as you asked about high temp shutdowns. Hope that makes sense the way I wrote it out.
Title: Re: Onan 7.5 diesel generator air filter change
Post by: mike and pat on January 21, 2014, 10:59:38 AM
wagonmaster, i have 1850 hours on my generator and while i was in Jacksonville, FL over Christmas I had it pulled and had the temp sensor replaced the belt changed, the hoses checked and the oil and filter changed, the fuel filter changed and the coolant flushed oh and the air filter changed. the quote was $1050 but they got done early and the total was a little over $700.
Title: Re: Onan 7.5 diesel generator air filter change
Post by: Wagonmaster2 on January 23, 2014, 08:12:25 PM
Ho Mavarick, boy do I ever feel like a dummy.   I have the Operator's Manual, which undoubtedly I have never read through the Trouble Shooting section.   Guess I figured I'd wait till I had a problem then start reading since I wouldn't be able to remember it all anyway.  Your explanation was crystal clear and made me read through all the codes in the Manual.  Appreciate all your time and trouble explaining all this to me.

Mike and Pat, you sure got a good deal on you gen maintenance work.  Was it at a regular Onan dealership or an independent?  Maybe I'll luck out when I reach a lot more hours on the gen.
Title: Re: Onan 7.5 diesel generator air filter change
Post by: captsteve on January 23, 2014, 09:04:01 PM
Mike and Pat,

I am trying to book feb 17th at Cummins Power South in Ocala for my gen service. I hope they give me the same price and service that you got. All of the checking that I have done shows them to be a first class operation as you said. I can't wait to se and learn some more about my coach.
Title: Re: Onan 7.5 diesel generator air filter change
Post by: mike and pat on January 24, 2014, 09:37:10 AM
Wagonmaster2 it was at Cummins Power South in Jacksonville, FL.