Highlander Hybrid A/C stops cooling when outside temp reading on console exceeds 107 deg F

hybridahohybridaho Member Posts: 1
edited July 2015 in Toyota
I read in a different vehicle forum that, in vehicles where the A/C condenser is mounted in front of the engine coolant radiator, when the engine coolant temperature reaches some near-overheat limit, the onboard system disengages the A/C compressor clutch so its condenser does not preheat airflow going to the radiator in an attempt to avoid overheating.

Is this the case with the Toyota Highlander (and specifically in a 2008 Hybrid Limited)???

I've recently been experiencing loss of A/C cooling when the center console outside temperature exceeds about 107 and the dashboard coolant temperature gauge is almost midway up towards H, but still closer to C. But once the outside temp reading drops back below 107, and I restart the vehicle, the A/C is once again cool.

Since coolant temperature is likely is impacted by higher outside temperatures, might the coolant temperature sender be failing or simply aged such that it is out of calibration, falsely indicating too high a reading?

Input from others with similar experience is appreciated. How difficult is it to replace the coolant temperature sensor? Where is it located (in case it's just a corroded connection!)?



  • thecardoc3thecardoc3 Member Posts: 5,614
    The AC compressor on your car is electric and driven by the Hybrid vehicle control ECU and the invertor assembly. If high ambient temperatures are causing it to shut down then the concern is that something with the hybrid system is getting too hot such as the invertor or the battery pack. What-ever is commanding the AC off should be easily seen in scan data by an experienced technician that has training on these systems.

    Corrosion in the coolant temperature circuit would typically cause the sensor voltage to be higher and therefore be interpreted by the PCM as a lower temperature than the engine is really at. While it cannot be blindly ruled out that corrosion could cause an alternate sensor path, reducing resistance and there fore reducing the signal voltage that would be a very uncommon condition. Besides if that was the case it would be creating additional symptoms that you haven't mentioned. Again scan data and in this case direct temperature measurement with an infra-red thermometer would allow that to be confirmed or ruled out without any prior disassembly or parts replacement.

    Due to the likelihood that your car is having a hybrid system issue, you really should be taking this to a shop that has qualified techs to work on it.
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