Engine hot A/C off 2009 Saturn Vue
 

I was receiving this message and after investigating realized that one of the fans on the fan assembly was not working. I replaced the fan assembly and now both fans work and the a/c blows cold. After the computer resets the car says engine hot AC off again. If I disconnect the battery for a moment and then reconnect it the air conditioner works and blows cold for about 15 minutes until the computer resets and again it says engine hot AC off and the AC stops blowing cold again.

Is the temperature gauge needle approaching the red?

Where on the temp gauge is the needle when those fans kick on?

Which engine is this?

Some vehicles are programmed to do so when environmental conditions and load on the vehicle combine to create a situation where the cooling system is not able to dissipate the heat fast enough.

Do you drive in stop n go?

Does the clutch on the compressor spin freely if you remove the belt? If not, the clutch may need replacing,

minimal average driving.


It is not over heating, or even getting hot. Just this message keeps coming up preventing the air from blowing. Disconnect the battery and it works great for a bit till the computer resets and boom, message again. I can literally pull over, disconnect the battery real quick, and in good to go with A/C again.

Engine coolant temperature (ECT) sensor
 

Checked on YouTube, and a lot of GM vehicles show this specific error. Others don't show the 'Engine Hot A/C Off' error, but other symptoms are the same -- cooling fans always running, cutting off A/C, and some with a CEL, apparently code P0118. See the link for how one 2007 Sky owner fixed it.

Do you have any codes? If so, which ones?

Indeed a faulty ects will cause the ECM to see the temperature as too high if the voltage drop across the sensor is close to zero or 0. Which would mean the temperature dependent resistance of the ects is very low or there is a short in the wiring or across the connector, possibly from corrosion.

However, in this case I would expect the dash gauge to read high and the fans to come on immediately upon startup or shall I say once the car enters closed loop control. It is possible that a different temperature sensing element is driving the dash gauge or that there are multiple temperature sensors on this vehicle. I don't know.

Saturn S-Series cars from the 90s were built with defective ects s. The same concept applies.

If it falls Short Circuit, or the equivalent of short circuit, resistance is low, indicates falsely high temperature

If it fails open circuit, there is no voltage drop across it and the equivalent reading corresponds to about minus 38 degrees until you fix it which leads to non-optimal engine performance in the summer.

Where is the needle on your temperature gauge? Does it change as you drive?