Bobcat T190 hydraulic temp out of range

531614087 Have a T190 in my lap again with a hydraulic temp light and a code 07-21. (hydraulic temp out of range, high) Little history here. Had this machine in my yard a couple of years ago with the hydraulics locked out. That time it ended up being a bad computer. It had the light then also. the machine sat in my yard for almost exactly a year because there is no dealership here and the service advisor harness was on backorder. When I finally was able to program and install the computer I still had the light and code. But the client decided to take it anyway and I was okay with that because I knew that the hydraulics weren't really overheating. I did change the temp sender at that time. Machine came back to me a couple of weeks ago to deal with a track frame problem. This morning I decided to look into the hydraulic temp problem and am now perplexed. I realized that i grabbed the wrong book (t140 manual). But it looks like the wiring schematic is accurate. I will believe anyone who tells me I am wrong. So it looks like it is just a two wire sensor (3300 and 3310). One wire should be 8 volt reference and the other wire should be the signal back to the computer. I have the 8 volts but I do not seem to have continuity back to the computer on the other wire. Here is the first thing I am confused about. I have it in my head that pretty much all 2 wire temp sensors work the same way. The v/ref is provided to the sensor and the voltage that makes it back to the computer is interpreted to determine a temperature. So... If 0 volts is seen by the computer it decides (I dunno... -40 degrees?). If all 8 volts are seen by the computer it decides (I dunno... One billion degrees?) If that is right... then just unplugging the sensor should show the computer 0 volts and and get rid of the out of range high code. It does not. Since it does not, my next thought is that somewhere the wire harness I have a short that is sending v/ref back to the computer but I don't have any voltage on the second wire. At this point, my lizard brain took over. Lizard brain step one is "hit it with a hammer". Step two is run an external wire from the sensor to the computer. When I did that the code 07-21 (hydraulic temp out of range, high) became code 07-22 (hydraulic temp out of range, low). So now what?

A 2 wire coolant sensor works buy measuring the resistance of the thermistor located in the coolant. the computer uses the voltage drop across the thermistor to determine the temperature of coolant. There is usually a chart the shows temp readings based on resistance. Did you use factory sensor?

Thanks for the reply. So I think that is what I basically said, just a little bit dumbed down. And I did use a factory sensor.

Strange, so you've eliminated any potential problem with the return wire. Is the 8v reference voltage staying put, when current is flowing, maybe you have green wire on 8v side, that fails under load. Only thing after that would be computer, which you changed.

I will check the 8v ref to make sure it is staying constant. I don't think it is because the code sets before you start the engine. And a problem on the v/ref normally would trip more than one code/light.

Arny L said: A 2 wire coolant sensor works buy measuring the resistance of the thermistor located in the coolant. the computer uses the voltage drop across the thermistor to determine the temperature of coolant. There is usually a chart the shows temp readings based on resistance. Did you use factory sensor? Click to expand... I don't remember ever seeing a chart for temp vs resistance (or voltage) in the manual. But it is pretty rare for me to work on bobcat machines. Is it in the workshop manual or somewhere on line? The sensor was factory. Btw, if anyone else is reading this, even though I do not normally work on bobcat machines, I have over a hundred bobcat factory service manuals. When my local dealership was shutting down they asked if I wanted them. I love service manuals, so I took all they had. Other than a couple of them, (the breaker manuals, and the two machines that i am obligated to work on)are useless to me. Pm me if you are looking for something.

C'mon forum, I offered free manuals.

the hyd temp sensor, as well as many other sensors, eng oil pressure, engine coolant, seat bar, and the RH aux thumb paddle are all on the same 8v system (there's a couple more, but i'm drawing a blank right now) any of the other sensors could be the problem. if i remember correctly, disconnect one sensor at a time (wait 15-20 seconds and see if your hyd temp returns to normal

Sorry to resurrect an old thread. But this machine is back in my lap for a new problem. But I am still obsessing about the hydraulic temp high problem. I raised the cab this morning and found this I am thinking that this is also a hydraulic filter or maybe a hydrostatic filter. If you look close at the filter head there is a one wire sensor in the filter head. One wire sensor in my mind is a switch. Either pressure or temperature. So I am wondering if this is my hydraulic temp high error code. Instead of

This sensor on this hydraulic filter