M7040 Thermo Sensor (Temperature Sensor) Removal

[Captain13]

I want to test my thermo sensor (termperature sensor). It's on the right rear top of the engine next to the air intake. I can't see how to release the wiring harness connector from the sensor. It's in a pretty tight spot with very limited visibility so I was hoping someone could tell me what the connector latch release mechanism is. I don't feel a release of any kind when I feel around it. Rather than break it, I thought I would see if anyone knows how to release the harness connector.

Thanks for any input.

 

[Russell King]

I don’t have any idea how to answer your question but you may want to get a small camera that links to your phone or tablet.

Search the internet for HD SEE and you should find an app and cameras

These can be fed into small tight areas and have lights around the camera to illuminate the areas

You may be able to see how it works


Sent from my iPad using Tapatalk

 

[Captain13]

Thanks, Russell. It is ridiculously tight in there. I'm going to go by the dealer and see if they can show me. They had a 7040 in the shop the other day with the hood off and no loader. Maybe this will give me some clarity. Right now, I will have to remove the intake hose (which I have done), a couple of small fuel lines and possible the three slow blow fuses and then try to move the main wiring harness more out of the way just to get to the connector. Poor design. It's probably like the hood though, once you take it off once, it's a pretty simple operation.

 

[200mph]

Curious what type of symptoms you are having to want to test the temp sensor.

Do you know what the sensor output should be at a specific temperatures? I'm thinking it is nonlinear so you might have to determine the equation that fits the line first to test at temperatures other than listed in manual. At least this is what I ran into when testing the output on one of my tractors a while back. If uncertain how to do this, post the numbers and I can calculate it for you.

 

[Captain13]

200MPH, I've been having a glow plug problem for quite some time and finally decided to try to track it down. Relay, fuse, wiring all ok. I don't see any issue with wiring. I'm wanting to eliminate the thermo sensor. It's possible that if the sensor is reading too high and the GPs don't come on until 32 F, then that could be the problem. Also, supposedly, if I unplug the sensor, the GPs will work (Open circuit condition). That's what this is all about.

 

[rentthis]

In that this is a test as opposed to a repair/replacement, is there enough of the wire exposed to cut it, do your test and reattach it with a stab lock or some other connector?

 

[Captain13]

Not enough room. Also, the connector is made to the harness with a thick rubber plug/strain relief that then feeds into the harness. Also, I would like to get it to a controlled cold temperature (around 32F or below) and can't do that with it installed.

I'm going to try to go by the dealer and see if a tech can show me on one in the shop that has the hood off hopefully without a FEL. The frame mounted brackets are really in the way. Too bad it's not in the center of the engine or up on the thermostat housing like some of the other models. The thermostat housing is easily accessible.

 

[200mph]

Captain13,

Sent private message.


Everyone else with GP or hard starting when cold.

I've found an issue with the relay sockets and the relays specified on a number of Kubota tractors. The relay socket uses larger 3/8" wide female terminals for the power side of the circuit (hi amp circuit for the GP) and the relay only has 1/4" male tabs.

The width of the tab is not the issue, but the thickness of the tab is. Without sufficient squeeze on the male relay tab, it can not support handling high current situations. In my case I modified the female terminal and have since purchased relays with larger terminals on the power side. The wider 3/8 tabs are 50% thicker than the 1/4" tabs found of most 40 amp relays.

Simply removing and replacing the relay from the socket is not sufficient enough test to verify good fit. The two smaller tabs for the relay control side have enough friction to mask the poor fit of the power side tabs.

I completely dismantled the GP wiring from Battery to GP, to find the root cause. The write up is on another popular tractor web site if anyone cares to read. For fear of violating any forum rules, it will not be posted here.

ADDED IN EDIT:

Generated the following post so all could see what I uncovered with the relay to relay socket mismatch.

http://www.orangetractortalks.com/forums/showthread.php?p=324709&posted=1#post324709

 

[Captain13]

I picked up a relay this afternoon.

I will give it a try. Worst case is I have a spare on hand.

 

[Captain13]

Great news. I figured out how to remove the sensor plug. I went by the dealer and they were of no assistance. They looked in the WSM and didn’t see a lock. I asked the to get a sensor and I saw the small ears on the side. So I came home, took a brass brush and bushe the connector across the top. There was a seam already visible but the brush highlighted a small wire in the seam of the connector to sensor mating surfaces. Using an Exacto knife gouging tool, I pressed firmly into the seam and pulled at a right angle and it raided the wire. I slide a small screw driver in and it slide up and unlocked. I did it with the hood on. It would be much easier with the hood off. Thanks for all the suggestions. With the two wire sensors going on several models now, I’m sure others will run across this problem.

 

[200mph]

The temperature sensor output with respect to the coolant temperature can be found in the attachments below.

I did a bit of curve fitting to the published data from the manual so the approximate output could be generated based on temperatures other than published.

Not certain it is helpful to anyone, but since I went through the trouble of generating might as well publish.

 

[Captain13]

I appreciate it, for sure. You don't think you need information like this until you need it.