Bobcat 331 overheating (but not really)

[lukeh]

I recently picked up a Bobcat 331 (2007 model) but am having some issues with the temperature.
In a nutshell, it shuts down because it thinks it is overheating, but it isn't even very warm. The temp gauge goes up in to the red, and that triggers the shutdown.

With the thermostat in, it takes less than 10 mins to get up to this temperature. At this point the thermostat has barely opened (the top hose is just getting warm). I've measured the temps variously at 110f to 120f (tested with infra red sensor).

If I take the thermostat out and run it, predictably it will run for 45 mins before getting to this temp, at which point the gauge has again gone in to the red, and it shuts down. I can take the radiator cap off and put my finger in there; the coolant is warm, not hot.

I have tried a new thermostat, but clearly it isn't the issue. I have tried a new (genuine) temp sensor, with no change in results.

I believe the problem must be electrical. My alternator charges at around 16 volts (which I think is too high), so I disconnected that completely and ran it without (nice constant 12.7 volts). Same result.

According to the wiring diagram, the coolant temp sensor wires go in to the display panel (sensible), but there is no further detail of what happens when in there.

It is throwing some codes, but the lcd display isn't readable, so I can't tell what the codes are.

I'm at the point of bypassing the stock temp sensor and gauge and putting in a secondary one instead; though i would prefer to fix this problem.

Any suggestions on what to try next? Very frustrating.

TIA

 

[lukeh]

I should add, that I tested the temp sender in a saucepan, taking resistance reading from cold to boiling, and it tests well within spec (spec is 500-3000 ohm, mine tested 970 ohms @ 22 degrees c, to 1650 ohms @ 98 degrees c).

 

[Jabonee]

Display controller is bad. :shocked:

 

[lukeh]

Based on crazy quotes, I decided to bypass the controller. I replaced the original temperature sensor with a 1k ohm resistor (I tested the sensor at 950 ohms at room temp). That tricks the control unit in to thinking it isn't hot, it also holds it at a constant temp.

I then installed a standalone (digital display, on the front ROPS upright, line of sight) temp gauge that I can keep an eye on. It's not ideal, but its $15 all in, rather than $1500 + for the controller, plus diagnostics, hauling to the dealer, programming, etc etc. So far I haven't seen the temp go much over warm........

 

[lupuseven]

Thank you for this tip!
saved me this week, resistor is in temp gauges are on the way and I was able to move the machine out of the way!

 

[lukeh]

As a follow up, over time I had to bypass more and more systems, including a manual switch for the aux hydraulics, different resistor for the hydraulic system level, fuel gauge, fuel solenoid and various others.
I eventually had the contoller/panel repaired by ISOSCELL. It cost me a little over $800 (which is way better than the $1500-$2000 I seen previously) and I was very torn as I had low expectations.

Turns out it's the best money I have spent on this machine. EVERYTHING now works as it should and all my bypasses have been removed.

I believe the cause in my case was the yard trying to jump start it with 24v instead of 12v. It cooked the controller and different components failed over time. Might have been something else, but that's my best guess.