# 2015 Diesel A/C not working at highway speeds



## Tomko (Jun 1, 2013)

Welcome aboard, at last.

It’s unlikely that the radiator fan would be running at the road speeds you mention. But it sounds like the ECM is commanding a shutdown to protect something in the system.

I’ve never experienced what you describe. But I’ve never driven at speeds above 65MPH for more than an hour at a time.

What I have experienced is the HVAC system detecting the evaporator starting to frost; and, automatically taking the system out of recirculate and into fresh air, in an effort to thaw the evaporator. Depending on the conditions, I’ve observed the HVAC system cycle through this as often as every eight minutes or so.

But I almost always have my HVAC fan set to the lowest speed. So that may be a factor.


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## snowwy66 (Nov 5, 2017)

A plugged cabin filter would cause an evap freeze.


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