Onan 7500 Gen Temp Sensor Repair

Onan 7500 Generator in my motorhome was shutting down about every minute or so and showing a fault code of 1 blink indicating an over temperature condition. While there can be several causes for this condition, the most frequent cause is a failed temperature sensor. This sensor is very difficult to remove and replace due to its location and the fact that it is made with a soft brass housing. This video shows how the original sensor can just be left in place and a new sensor can be installed once a port in the thermostat housing is tapped to allow the new sensor to the screwed in place. If this is your problem, you will find this video most helpful.

[@user-qi9xv6jf4e]

Since installing the new temperature sensor as shown in the video, we have taken an extended trip in our motor home running the generator in excess of 24 hours. It ran overnight on two separate days and did NOT shut down at any time. This is a good practical test that the sensor is performing properly.

[@mmkmike]

Good job. I like the alternative practical thinking.

[@TruckingTrucks]

Appreciate your time to make this video and thinking outside the box! I will remember the Newton repair when telling my friends. Thank you!

[@user-qi9xv6jf4e]

Glad it was helpful!

[@insightsbk]

Outstanding outside the box thinking

[@cbcarper9681]

Thank you for showing me all of that. I have the exact generator. I really appreciate it.

[@ToddM452]

Perfect! Good and solution and video.

[@zjtr10]

Thank you for taking the time to make the video. I believe you have shot yourself in the foot when you changed the location of the temperature sending unit. As you have it now you are measuring the temperature of the water past the thermostat. If the thermostat sticks shut the sending unit will never see hot water and shut the engine down.

[@user-qi9xv6jf4e]

To each his own. If you don't want to use this modification its up to you, but I assure you if you get to the point where you can't remove the original temp sensor, you will be looking for other options. The sensor only is responding to a too high a temp and shuts the gen set down. So if the thermostat does stick shut then the temp of the gen coolant water and surrounding metal is going to heat up very quickly, the sensor in this new location will see this elevated temp and shut it down. I know that will happen as I have shared in the video.

[@Geneexpert]

@@user-qi9xv6jf4e I needed to replace my temp sensor as well for a different code and I was able to get the sensor out but the tip broke in the housing, so I did your modification and now I get error 1 overheat. So I took it back apart and drilled a hole in that cavity put it back together and still get the same error. 2004 tiffin phaeton 35rh with 7.5 onan 60 hours on gen. your thoughts?

[@user-qi9xv6jf4e]

@@Geneexpert Did you also replace the thermostat. If it is stuck closed it will also cause the gen to overheat and give the same error. Did you run the gen with the top panel at least laid back in place (doesn't have to be bolted down)? If the panel is not put back in place then the fan will not be pulling air through the radiator and it will overhear. Has the radiator been flushed out recently? Is the outside of the radiator dirty? Just some thoughts to think about.

[@insightsbk]

Just completed modification thanks for creating this video. I do have one question did you cut a hole to allow fluid to sensor?

[@user-qi9xv6jf4e]

I did not cut a hole to allow direct contact with the coolant. I believe I covered that in my video.

[@frankram2303]

What code did you get when you had the problem??? Thanks

[@garykennealy3245]

any chance you havve a part number for that housing, ours is different and I am out of options. Thank you

[@user-qi9xv6jf4e]

Gary sorry for the delayed response as I don't monitor this channel very often. As to the part number for the "housing" I am assuming you are talking about the housing that is removed to get at the thermostat and which I was able to tap out the hole that was already there. Unfortunately I don't have that part number but you might be able to google Onan Genset 7500 diesel year 2005 and get to a parts diagram and find it that way.

[@insightsbk]

How is mod holding up?

[@wayneriley7315]

Did the gen shut down when driving with basement ac running

[@user-qi9xv6jf4e]

Sorry, I don't monitor this site very often, but to answer you question: I don't have a basement AC unit on my motorhome but I do have 2 overhead AC units. I have run one or both of them at times while boondocking overnight. On these occasions, the gen has run for at least 8 hrs without shutting down. At times We also run it while driving without any shut downs.

[@timmysrvlife]

Would you please share the part number of temp sensor?

[@user-qi9xv6jf4e]

Sorry I don't monitor this very often. I purchased a kit on Ebay that included the sensor. The sensor # was Sender 193-0318. Hope this helps

[@timmysrvlife]

@@user-qi9xv6jf4e Thanks!

[@mountainman5025]

Using a tripod creates a less shaky video.