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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 15197
Experience:  Certified on Onan and Generac generators
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I have an onan 12.5HDCAB-A I am having code 1 shortly after

Customer Question

I have an onan 12.5HDCAB-A
I am having code 1 shortly after starting, maybe 10 minutes after start up. (code 1 engine temp to high). So it seems to be over heating really fast. Now I have changed oil, fuel filter, water temp sensor, thermostat and gasket just as routine maintenance. I have made a couple small modifications as well. first I installed a secondary fan that blows up from under the trailer onto the radiator. I took the radiator to a well known radiator shop and had them flow test it, turned out good. The owner of that shop made a suggestion to create an extra fluid hose that would run from the drain plug of the radiator back up to the overflow bottle. So I did that and filled it up with new coolant and tested again. sure enough ten minutes later the over flow bottle filled up to the top and flowed over, then it shuts off with the same code. I know that if the sensor wire gets grounded out it will peak to the hot reading and the PCM will shut it down. So my question is WHAT AM I MISSING?? is there an air bubble? causing high readings? is there a bleeding procedure that is not in the manual? Or do I need look for a short. Could the PCM be faulty? Now mind you it is 100 degrees in Oregon today.
Please Help!!!
Submitted: 2 years ago.
Category: Small Engine
Expert:  Hank F. replied 2 years ago.
My name is ***** ***** I am going to assist you with this.
That sounds like your drive belt may be broken or slipping.
It is also possible that the water pump is bad.
Customer: replied 2 years ago.
Well the water pump spins of with the belt off. The belt was a little loose so i am putting a new one on today. I am also gonna do a head gasket leak test.
I dont know if the water pump is plastic or metal on the impeller. But there are no signs of plastic in the coolant.
So we will see
Expert:  Hank F. replied 2 years ago.
If the drive belt were too loose, the water pump may have been slipping.
Customer: replied 2 years ago.
Well. So you would not believe what i came out to be. Now being an inclosed motor that depends on air cooling as well as liquid cooling. I piece of foam that was on the top of the case around the generator had fallen down below the sucker squirral cage fan and blocked all the exiting air, in witch caused heat to build up inside the case. Runs great now even in 100 degrees.
Now both of us will log that scenario in our heads and be able to diagnose better in the future LOL .
Thanks for the help
Expert:  Hank F. replied 2 years ago.
I'm glad you found the problem.