Onan 7500 - 2005 Journey - temperature sensor removal

[Gyroscopic]

Hi.

I worked on removing the temp sensor today in a Onan 7500 QD. I use the hot cold technique and got the threaded part out without trouble, but the sensor tip stayed in the housing. Has anyone dealt with this? I’m reluctant to push it inward for fear I might not catch it and it falls into the water pump. But I’m not sure how to push it outward exactly. I got all the threaded part out, so in theory it should be smaller and pass by the threads if dislodged.

Any thoughts?

Thanks.

[Mile Marker 42]

Originally Posted by Gyroscopic

Hi.

I worked on removing the temp sensor today in a Onan 7500 QD. I use the hot cold technique and got the threaded part out without trouble, but the sensor tip stayed in the housing. Has anyone dealt with this? I’m reluctant to push it inward for fear I might not catch it and it falls into the water pump. But I’m not sure how to push it outward exactly. I got all the threaded part out, so in theory it should be smaller and pass by the threads if dislodged.

Any thoughts?

Thanks.

Yep, there is a thread here on it that should be able to help you. You have to get down to thread #11 before any pictures. https://www.irv2.com/forums/f258/ona...em-312383.html How did you pull your generator? Got any pics?

[Gyroscopic]

Hi.

Thanks for the referral. That is a thread I read and I’m trying to avoid pulling the head. Mine is different in that I got the top 2/3 of the sensor out. The threaded portion is not stuck in the housing. It seems it should be able to be dislodged somehow. Ran out of daylight today to mess with it, so wanted to consult the experts overnight.

[Gyroscopic]

Just in case someone needs the info later...

To remove the tip of the sensor I wound up putting some duct tape on the inside of the water manifold so that I couldn’t push the sensor tip into the engine. Then I took a screw driver and removed corrosion around the edge of the sensor in the “gap” where water should be. I messed with a drill some, but didn’t want to get too rough with it.

Finally I took a flat tip round punch and put it in the sensor hole and put my finger on the inside of the water manifold and bumped the punch. It came out easily and then I fished it out the top without issue.

Used a screw driver to clean the area where the sensor goes. Lots of scraping and vacuuming and scraping, but got it clean. Removed the duct tape and put in the new sensor.

Got the generator back in the Journey and need to hook up the top side electrical and put coolant in before hopefully having it fixed and reliable.

Thanks!

[radar]

There’s a guy on here called Fireup and he went through the process you are going through. See if you can dig up his post or contact him directly.

Good luck.

[FIRE UP]

Gyro,
I just got to this thread. Yeah, sometimes goofing around with that temp sensor can be one bag of worms. For some, the lucky ones, they get in there and, just like a spark plug in a 6 month old lawn mower, it unscrews without any issues and the new one zips right in. But for others, like me and you, yep, it's gonna fight us all the way.

You've checked out my pics and saw what I had to go through. Not fun. But, ours has been working pretty much problem free ever since I did that job, over 7-8 years ago. For those of us that have the gennys on a slide out, this kind of work is at least lessened in turmoil and heartache. For those that have to attack this kind of repair, on a genny that DOESN'T slide out, well, I feel for ya for sure.
Scott

[Gyroscopic]

Originally Posted by FIRE UP

Gyro,
I just got to this thread. Yeah, sometimes goofing around with that temp sensor can be one bag of worms. For some, the lucky ones, they get in there and, just like a spark plug in a 6 month old lawn mower, it unscrews without any issues and the new one zips right in. But for others, like me and you, yep, it's gonna fight us all the way.

You've checked out my pics and saw what I had to go through. Not fun. But, ours has been working pretty much problem free ever since I did that job, over 7-8 years ago. For those of us that have the gennys on a slide out, this kind of work is at least lessened in turmoil and heartache. For those that have to attack this kind of repair, on a genny that DOESN'T slide out, well, I feel for ya for sure.
Scott

Well the good luck ran out. Got the generator back in and reconnected and it won’t crank. When the start button is hit, I believe the fuel pump does its clicking - loud and then softer after a few clicks. Clicks probably three times per second while the switch is pressed. Same sound it makes when it is held in the off position, which makes me think it is the fuel pump.

Put a charger on the batteries for a long while and still no cranking. The generator has always spun and started right up. We didn’t mess with any electrical on the generator itself aside from the wire to the temp sensor, the plug outside the generator, and the 5 wires into the generator.

The two fuses under the radiator fill door seem fine. Are there any other places that might be preventing the generator engine from even spinning?

[radar]

Originally Posted by Gyroscopic

Well the good luck ran out. Got the generator back in and reconnected and it won’t crank. When the start button is hit, I believe the fuel pump does its clicking - loud and then softer after a few clicks. Clicks probably three times per second while the switch is pressed. Same sound it makes when it is held in the off position, which makes me think it is the fuel pump.

Put a charger on the batteries for a long while and still no cranking. The generator has always spun and started right up. We didn’t mess with any electrical on the generator itself aside from the wire to the temp sensor, the plug outside the generator, and the 5 wires into the generator.

The two fuses under the radiator fill door seem fine. Are there any other places that might be preventing the generator engine from even spinning?

So that clicking is the pre-heat. Just for giggles and grins press and hold it for a minute or so in the start position. It might be the temperature sensor is sensing it is cold....even if it isn't.

[FIRE UP]

The engine ECM receives both COLD and WARM signals from the temp sensor. The ECM also decides when to allow the starter to crank that little 14 hp Kubota diesel . The criteria for allowing it to crank is in the service manual .
There is a stepped chart that lays out the pre-heat timing sequence, that Will take place before the starter is allowed to crank. The colder the ambient temperature is, The longer ger you must hold down the START switch. If your outside ambient temp is around 60 or higher, that gen should crank right when the button is pushed . But, if your outside temp is say, oh maybe 40 degrees or so, that start switch has to be held down for around 10 or more seconds, maybe more, it's been a while since I studied the chart.
But, as for your no crank issue, I'd start by checking both battery cable connections at the backside of that gen.
Scott

[Gyroscopic]

Well the advice you two provided was right on. Asked my dad to hold the button longer than we had yesterday (I’m out of town) and he was able to get it to start. Helped that it was warmer today and was able to get it to pump the air out of the fuel lines.

Thanks so much for the assistance. Once we complete the radiator flush, and put in the antifreeze, I can see if the replacement temperature sensor actually solves the random shutoff problem.

[radar]

Originally Posted by Gyroscopic

Well the advice you two provided was right on. Asked my dad to hold the button longer than we had yesterday (I’m out of town) and he was able to get it to start. Helped that it was warmer today and was able to get it to pump the air out of the fuel lines.

Thanks so much for the assistance. Once we complete the radiator flush, and put in the antifreeze, I can see if the replacement temperature sensor actually solves the random shutoff problem.

I love a happy ending. Wait till it’s minus twenty and you have to hold that switch. Bring a coffee. .

Cheers.

[FIRE UP]

Coolant temp > 120° 0 seconds
Coolant temp 50° 5 seconds
Coolant temp 23 10 seconds
Coolant temp < -4 15 seconds

Scott

[ladagobago]

Originally Posted by FIRE UP

The engine ECM receives both COLD and WARM signals from the temp sensor. The ECM also decides when to allow the starter to crank that little 14 hp Kubota diesel . The criteria for allowing it to crank is in the service manual .
There is a stepped chart that lays out the pre-heat timing sequence, that Will take place before the starter is allowed to crank. The colder the ambient temperature is, The longer ger you must hold down the START switch. If your outside ambient temp is around 60 or higher, that gen should crank right when the button is pushed . But, if your outside temp is say, oh maybe 40 degrees or so, that start switch has to be held down for around 10 or more seconds, maybe more, it's been a while since I studied the chart.

Scott

Hi Scott, Well I am in the process of find why My 7500 QD won't keep running. It starts up with pulling the Governor full, fuel pump run, Stator windings measured and OK. OP switch works normal, But it shuts down after a few seconds. I can keep it running by manually pushing on the governor rotor but not converting to AC. I used a HF lift platform and a come along to pull unit out of MH.
I did take apart the controller assembly to clean the boards which were cover with diesel dust but that did not help. I am now looking at the temp sensor to find out if it is defective. Do you know any way to test the sensor. Is it a binary or variable resistor./? I am at a point where I think it could be time to send the entire inverter/controller out for repair.

[FIRE UP]

Originally Posted by ladagobago

Hi Scott, Well I am in the process of find why My 7500 QD won't keep running. It starts up with pulling the Governor full, fuel pump run, Stator windings measured and OK. OP switch works normal, But it shuts down after a few seconds. I can keep it running by manually pushing on the governor rotor but not converting to AC. I used a HF lift platform and a come along to pull unit out of MH.
I did take apart the controller assembly to clean the boards which were cover with diesel dust but that did not help. I am now looking at the temp sensor to find out if it is defective. Do you know any way to test the sensor. Is it a binary or variable resistor./? I am at a point where I think it could be time to send the entire inverter/controller out for repair.

Hey Ladago,
Well Sir, nope, I'm not savvy enough to know just how to test those sensors. If I recall, the book (Onan service manual), kind-a spells out what kind of tests provide a given set of results. The testing of the sensor is probably in those pages somewhere.
Scott