Lake Havasu City generator repair

[David T. Richelderfer]

First, the problem: The generator starts fine, but shuts down after about five minutes.  It will start again, but will again shut down after five minutes.

The diagnosis:  I am getting a first-level fault code with three flashes.  The three-flash first-level fault code indicates the shutdown is due to "some other abnormal condition."  One flash indicates the shutdown is due to high temperature.  Two flashes indicates the shutdown is due to a loss of engine oil pressure.  Two flashes sounds bad, one flash sounds potentially bad.  But the three flash code means keep looking.

After pressing the generator switch to its STOP position once I get the second-level fault code.  I am getting a two flash-four flash code more commonly called a No. 24 error code.  The No. 24 error means the coolant temperature sender is not reporting the engine temperature to the generator's brain.  So, either the sensor itself needs replacing or the electrical connection from the top of the sensor to the generator brain has been lost.  This error does not mean the engine is too hot - it means the generator's brain is not receiving temperature information, so it is shut down to prevent overheating which will ruin the engine.

The solution:  After visiting several RV shops in Lake Havasu City, I was finally told who to go see.  Almost all of the shops can do the repair, but if a shop runs into a problem the shop techs are unable to solve, then they all go to Bill McVicker at Challenger Automotive, Inc. at 781 N Lake Havasu Ave, Units 4 & 5, 928-855-5969.  Bill specializes in generator repair, and knows Onans inside and out (so he claims).

His points of discussion:  1. Almost always this error means the temperature sender requires replacement.  Almost never is it an electrical connection problem outside the temperature sender unit.  Typically, the temperature sender units get corroded from not changing the coolant regularly.
2. The temperature sender unit is located where it is almost impossible to service without removing the generator from the coach.  The temperature sender is located on top of the engine, passenger side of center, and towards the rear of the coach.  The clearances are too tight to easily get the generator's top and side panels removed to provide access.  And even if the panels are removed, then the shroud which directs the cooling fan's air stream partially hides the temperature sender unit.
3. Removing the generator takes about two hours.  Replacing the generator also takes about two hours.  While the generator is out, also replace the belt and the thermostat.  These three parts' cost is cheap relative to the cost of removing and replacing the generator.  Replacing the temperature sender unit, belt, and thermostat takes maybe an hour.  These three parts cost around $100 or less.
4. If it is a diesel generator, then usually that's all there is.  If the generator has not had its valves adjusted for years AND many thousands of operational hours, then consider a valve adjustment.  It the generator purrs when running, then probably no valve adjustment is necessary.  Propane generators are a different story.  They run hotter and the valves will warp, thus requiring more valve adjustment or replacement consideration.

I have the parts on order and expect to have the coach in his shop early next week, December 30 or 31.  It should be a five to six hour, all done in one day job and cost $500 TO $600.  I will let you know the final results and my reference conclusions relative to Challenger Automotive's work.  For reference, this is a 12.5kw diesel generator, HDCAB 11506 A with S/N J020426993.

[Edward Buker]

David,

I have posted some info regarding the sensor ohm values at various temperatures. When I was working on my overheat issues, which could have been a faulty sensor, I added a wire length to the sensor with a male and female spade lug plug and located it at the removable door location. If you had sensor errors you could get some sensor measurements in the future without pulling all of this apart. There are photos of the sensor, the added wiring, and sensor values vs temperature. You may want to add this inexpensive adaptation while yours is out and the sensor is accessible.

There are older posts referencing this.

The question I have for you and your expert, is there any generator bearing lubrication or maintenance that he would also recommend while the genset is out and accessible for the generator end of things.

Later Ed

[David T. Richelderfer]

Thank you, Mr. Buker, for your reply, good information on this project and many others as well, and your very reasonable question to ask my "expert," vis-à-vis, generator bearing lubrication or maintenance.  As long as we're in there, like the doctor says, "We should take a look around."  I shall try to remember to ask Bill a mostly generic question about anything else we can look at while it's open for easy fixing and/or maintenance.

[David T. Richelderfer]

I checked with Bill at Challenger Automotive about the question of looking at anything else inside the generator while it's on the ground.  He quickly indicated all the moving parts are enclosed and have sealed bearings.  So... I suppose we can visually inspect the generator from end to end, and perhaps wiggle things to make sure they are not loose.  The other motorhome/Onan owner who called while I was chatting with Bill last Friday has already had his problem fixed and is gone.  All his parts were on hand in the city.  My repair parts have arrived and my appointment is firm for Monday morning.

[David T. Richelderfer]

Follow up:  The generator repair is in the history books, and also in the bank books... I might add.  The problem diagnosis was correct.  (Mr. Buker)>>  On the ohm meter, the faulty temperature sender reading was 1600;  the new sender has a reading of 6.06.  The old belt did show some wear, but was not in bad shape.  The belt was only slightly loose from where it should have been.  The thermostat looked new, but we replaced it anyways.  The thermostat was the larger of the two possible sizes found in this model generator.  The plastic coolant reservoir is in good shape - no cracks could be found.  The coolant hoses all looked new.  The plastic squirrel cage fan shroud was in good shape - no cracks found.

The repair did involve complete removal of the generator from the nose of the motorhome.  4.75 hours labor @ $80 is $382.50.  The temperature sender ($16.57), belt ($18.46), 54mm thermostat ($51.01), thermostat gasket ($2.48), coolant ($6.99), and 1-day freight to get the thermostat quickly ($30) is $125.51.  Throw in a few shop supplies ($5.16) and Arizona Sales Tax ($7.50), and the total bill is $520.67.  And that is just about what I was told the repair job would cost.  Had I not elected the 1-day freight (during the Christmas and New Years period), then the total bill would have been $490.00.

The generator starts easily and purrs like a kitten.  The repair job is only a few hours old, and so far, so good.

[Karl Welhart]

David,

Great follow-up, thanks.

[Larry Fritz]

David, I followed your lead and had my 7.5KW Onan our our 98 Patriot 37' serviced. New belt, new temp sensor, new coolant, and replacement radiator. My radiator was showing sings of thinking about clogging.

Two interesting and costly things happened as well:

1. The generator would not come out of the slide. Reason, Beaver welded four supports for the front cap cover in front of the generator. Welded to the slide itself. I called BCS service and confirmed this.  But, Bill McVicker was very creative and figured out that the two large rollers on the back slide area were creating the inability to pull out the generator slide from the chassis. We analyzed that and decided to drill a 1" diameter hole in the slide that perfecting aligned up with the roller. That hole allowed a wrench to get in and remove the roller (shaft) bolt. Repeated the other side for two total.  With everything disconnected and a lift cart under the front of the generator and  out it came.  No cutting of the four welded supports and subsequent rewelding after servicing. (Good thing as we had to take it out two more times as things turned out)

2. The NEW ONAN THERMOSTAT proved to be defective. It did not open very far and the generator would heat up to 240 degrees within 10 minutes and automatically shut off. (Bill says in his over 30 years, this is the first ever defective brand new Onan thermostat that he has ever seen not work)  I made the decision to put my old original thermostat back in and the generator works perfectly.

To sum things up, if anyone reading this has a coach configuration exactly like mine, consider drilling the two holes and forget the cutting and welding.

Bill was wonderful to work with. Very informative, interesting, and genuine nice guy.  

Thanks for the recommendation.

[David T. Richelderfer]

Larry - You're welcome.  I hope the repairs work out for you.

On the same subject, I said I would report on my generator's ongoing health... and here is (I hope) a final report.  On my way home to Oregon from Arizona the generator was shutting down and giving me a one-blink code.  For my generator the one-blink code indicates an overheat condition.  I decided on the drive to Oregon that I would stop by BCS to have the coach generally looked over because I was noting some other issues as well.  This time the generator was indeed overheating... and because its coolant was about gone.  After another expensive extraction of the generator, the BCS technician determined the crimp-style hose clamps on the hoses near the water pump and thermostat housing were not crimping properly, thus allowing coolant to leak out.  I don't know how many times my crimp-style hose clamps have been loosened and re-tightened, but apparently they were loosened and re-tightened one too many times.  The BCS technician noted that he always removes the crimp-style hose clamps and replaces them with the screw-style hose clamps.

The problem with the crimp-style hose clamps is when they are put on the hoses the metal is bent to make the clamps tighten around the hose.  When they are removed the metal is bent to loosen the clamp from around the hose.  Like a wire that is continually bent over and over at the same point, the metal gets weakened and will eventually break at the point of continuous bending.

Soooo... if you are into your generator and have the opportunity to change those crimp-style hose clamps, then do it and save yourself another expensive stop at a shop later on.