I have a 2008 Kubota BX25 with a BX23 engine. While I was digging with the backhoe, the engine coughed causing me to look at the gauges. The Temperature gauge was pinned at hot. I shut it off pronto. I checked and the coolant was full and normal in radiator ( after it cooled) and in the overflow tank. I pulled the temperature sensor and its resistance was .7 Ohms, a near short. I've got a new one on order. I changed the thermostat. I filled the near empty fuel tank to about 1/4. I changed the fuel filter. Now I have no way to run my BX25 while knowing the actual temperature ( a must). It has the older odd shaped gauge shown in the photo. I ran it about 5 minutes and used a laser temperature gauge pointed at the head and it seemed locked around 125 degrees. That seemed good. Maybe the thermostat I changed was stuck closed? Does anyone know where I can get the old odd shaped temperature gauge? And how its removed? Any thoughts appreciated.
2008 Kubota BX23 engine in BX25 Temp Gauge Stuck pinned HOT
- Thread starter pgrovetom
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North Idaho Wolfman
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Check your ground wires this can happen from loss of ground to dash.
If you removed the wire to the sensor and it didn't change, then its a dash or wiring issue and not a sensor issue.
If you removed the wire to the sensor and it didn't change, then its a dash or wiring issue and not a sensor issue.
85Hokie
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Thanks, Any idea where the dash ground is connected to ground? I believe here there is a harness leaving the dash.
That is what I used after changed the thermostat. It gave me confidence the head temperature was holding after coolant began flowing. I had the radiator cap off first see if the coolant began flowing once the new thermostat opened. I also put my finger in the radiator coolant and waited and it began getting warm so I knew coolant was flowing as the engine warmed. Then I closed the cap monitored the head and block temperature with exactly the device you show and it appeared it was running in the 130ish range depending on where I pointed the laser thermometer. So is looked like the cooling system was working ok. Only the gauge stuck on HOT. The fuel gauge works ok so I still wonder if its a bad temperature gauge or maybe its ground.
I can't help but wonder why the fuel gauge seems normal if the dash ground is open. I suspect the thermostat has a thermistor in it where the resistance to ground varies with temperature. If mine is ok ( .6 Ohms cold) , then low resistance means cold and its resistance goes up with heat. That would suggest I could just ground my sensor lead while running maybe through 5 ohms or so for safety and see if my gauge comes down. Anybody have a BX23 electrical diagram? If all that is true it might suggest a bad meter or the meter not connected to 12V. I say this because the current through the meter flows from the grounded sensor through the meter to 12V. This assumes its just an analog meter measuring resistance to ground which measures temperature. Low resistance = cold and higher resistance = hot. Thoughts?
hmm, did the needle go back to 'cold' with the power off ? If so,gauge is OK. A 'super hot' reading indicates the sensor wire is shorted to ground. According to the diagram I grabbed, it's the typical +12v-->meter-->sensor--> ground setup. The owner/service manual should have a chart of sensor resistance vs temperature. You should check the data for both BX23 and BX25 sensors ! They could be different.
BTW if the needle IS pinned super hot with no power , tap,tap, TAP the gauge. That may free the needle.
The needle gauge is pinned all the way to HOT with the power on or off with the sensor connected or not to lead. The sensor Ohm reading out of tractor is about .6 Ohms. My Ohm meter lead shorted is .1 Ohm. Today I'll heat the sensor with a heat gun and see if rises. My ordered sensor
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For BX25, the temp sensor ranges are (actual thermo unit):
220 ohms, dead cold (minimum on gauge)
70 ohms, start of red region on gauge
3 ohms at maximum temp range (off scale on gauge)
So a short in the thermo unit, or a short to ground of the wire (20WY - White/Yellow wire) to the thermo unit should give close to zero ohms
220 ohms, dead cold (minimum on gauge)
70 ohms, start of red region on gauge
3 ohms at maximum temp range (off scale on gauge)
So a short in the thermo unit, or a short to ground of the wire (20WY - White/Yellow wire) to the thermo unit should give close to zero ohms
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North Idaho Wolfman
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Just for clarity sakes, why do you think or know your BX25 (which should have a D902 engine) really has a BX23 (D905 engine) in it?
If the wiring has a short to ground, internally or in the wiring that would explain your pegged guage when it's powered but not when it's off.
If the wiring has a short to ground, internally or in the wiring that would explain your pegged guage when it's powered but not when it's off.
Ok, looks like bad sensor. I had the electrical diagram ( included here) and the gauge is connected via the harness to ignition 12V . So if the gauge is not broken or open, I should see the 12v coming down to to the removed temp connector. I'll investigate when it warms up.
Just a sanity check, the temp sensor is near the front of the engine ( If you are seated on the tractor - front left) on the opposite side from the oil filter screwed into the head which is lower front right. The oil pressure sensor is on the oil filter side ( right) and near the oil filter and requires a 24mm socket. Is that correct. My owners manual doesn't show anything. I've got mixed input from the internet searches a the AI from Google got it wrong. Youtube video got it wrong.
Wrong:
Google AI "The Kubota BX23 temperature sensor is located
on the engine's cylinder head, near the rear, on the same side as the oil filter. It may also be found near the thermostat housing or screwed into the engine block, so checking the repair manual is recommended for the exact location"
"The location of the temperature sensor for a "bx25" depends on what it is. For a Kubota engine (like the L2850), it's on the back of the cylinder head, near the thermostat housing, possibly screwed into the engine block."
Wrong --
The top of the engine has a white label that clearly says BX23 but I purchased a BX25 with backhoe in 2008.
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I want to verify the sens location having got bad info on internet searches. This is the one that appears to be the thermo sensor but I have the sensor claimed to be the thermo on a Youtube video and close to where Google AI says it is.
I believe this is the thermo sensor - front of engine on left front
I believe this to be the oil pressure sensor. On the back right near oil filter. For some reason all internet sources suggest this the thermo sensor. I have also seen its near the thermostat but there is no sensor near my thermostat. I bought a BX25 manual from "sellmanuals" and got ripped off. I never got the link to download it. Any help appreciated. Kubota seems to put things all over the place and confuses Google AI and the Youtube guy straight up claimed the oil sensor was the thermo sensor. It seems.
I believe this is the thermo sensor - front of engine on left front
I believe this to be the oil pressure sensor. On the back right near oil filter. For some reason all internet sources suggest this the thermo sensor. I have also seen its near the thermostat but there is no sensor near my thermostat. I bought a BX25 manual from "sellmanuals" and got ripped off. I never got the link to download it. Any help appreciated. Kubota seems to put things all over the place and confuses Google AI and the Youtube guy straight up claimed the oil sensor was the thermo sensor. It seems.
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So I took the dash board out and made an important discovery. The fuel and temperature arms are rotated by what appears a small black servo. Both are identical. There is electronics including what looks like a custom chip controlling everything. Its probably not cheap. The fuel arm and needle move easily with very little effort. Its easy to see how a small servo could turn it and set it where it wanted. On the other hand, the temperature gauge arm and needle will turn with some effort that is far more than the fuel. The servo on the temperature gauge appears stuck quite tight. Turning it has lots of resistance. I doubt this is normal. I wonder if there is a place that has old used parts for this BX23 model dashboard and I could try just changing the servo. It looks like I could pop it out and replace it. It also has 4 tiny screws on the back and I'm going to look inside. Any ideas?
Update: So I took the dash board out and made an important discovery. The fuel and temperature arms are rotated by what appears a small black servo. Both are identical. There is electronics including what looks like a custom chip controlling everything. Its probably not cheap. The fuel arm and needle move easily with very little effort. Its easy to see how a small servo could turn it and set it where it wanted. On the other hand, the temperature gauge arm and needle will turn with some effort that is far more than the fuel. The servo on the temperature gauge appears stuck quite tight. Turning it has lots of resistance. I doubt this is normal. I wonder if there is a place that has old used parts for this BX23 model dashboard and I could try just changing the servo. It looks like I could pop it out and replace it. It also has 4 tiny screws on the back and I'm going to look inside. Any ideas? If you look at the second photo, you can see the 2 small round black servos that drive the meter needles. The case was very dirty but the electronic boards and everything around the bad servo looked very nice. No sign of water intrusion or dirt or electronics issues.
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For the sending units.
If you have a wiring diagram the wire colors will confirm the information you’re looking for.
But the oil sensor should not corrode so I say the temperature sensor is the first picture, and the second looks like a pressure sensor to me.
If you have a wiring diagram the wire colors will confirm the information you’re looking for.
But the oil sensor should not corrode so I say the temperature sensor is the first picture, and the second looks like a pressure sensor to me.
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North Idaho Wolfman
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Ok you've been sucked in by Kubota's odd labels.
You DO NOT have a BX23 engine you have a BX25 don't call it anything else.
You can get a BX25 manual off Kubotabooks.com for free just click the link.
The thermo sensor is on the top rear right of the engine and the oil pressure is the left rear lower side.
Now don't get to confused as your engine is installed in the tractor backwards.
So for you thermo sensor is to top front left of the tractor.
You don't need an instrument cluster for a BX23, you need an instrument cluster for a BX25.
EDIT: You really need to post a picture of the tractor your working on and the serial number, because that's not a dash out of a BX23 or a BX25 it's a BX24 dash.
You DO NOT have a BX23 engine you have a BX25 don't call it anything else.
You can get a BX25 manual off Kubotabooks.com for free just click the link.
The thermo sensor is on the top rear right of the engine and the oil pressure is the left rear lower side.
Now don't get to confused as your engine is installed in the tractor backwards.
So for you thermo sensor is to top front left of the tractor.
You don't need an instrument cluster for a BX23, you need an instrument cluster for a BX25.
EDIT: You really need to post a picture of the tractor your working on and the serial number, because that's not a dash out of a BX23 or a BX25 it's a BX24 dash.
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Yes, I purchased a BX25 but the motor says BX23. I'll post a picture. But I found my problem. I took the servo motor back off and found the tiny gears teeth were damaged. The stepper gears have a stop and tiny gears stepped by solenoids. The break in the tiny gears seem to cause the meter to jam due to slippage and the stop. It looks like slippage or sticking as the gear damage goes by, moves relative to the zero stop . It had just slowly moved to HOT and stuck. When I turn the Fuel gauge carefully, it moves in tiny steps smoothly. So the chip looks at the sensor voltage and pulses solenoids moving the needle a tiny bit. Its not an old fashioned analog gauge, its a solenoid driven stepper based on tiny plastic gears. I think I need to buy a new console as the tiny gear damaged gear teeth is irreparable and finding a replacement is impossible. Its so small it takes a magnifying light to see the gears. I actually moved the good fuel gauge to the temperature side and it worked with a good gear.
I thought about getting a marine temperature gauge off Ebay and designing a circuit to convert the Kubota sensor output to the new gauge calibrated but the effort and odd gauge would funky. I'm an electronic designer so might find it but a new $400 console would be more costly but quick.