A/C Trouble

[wmattharris]

We have a 2019 Mack GR64F in our fleet that has some climate control issues. The driver states the the system runs fine until around 11:00am then blows only hot air until around 2:00pm or 3:00pm. This truck has less than 60,000 miles on it and I just changed the filter and cleaned the coil. This morning I hooked my gauges to it again just to be sure and the pressures were almost perfect (for the temperature and humidity) however the compressor is short cycling on and off. This usually would point me toward some air flow restriction but as I said it has a new filter and clean coil. I am just wondering if this might be a common problem for these trucks with hopefully an easy fix. Thank you in advance for your help.  

[Onyx610]

I heard there was a common issue with the hvac control module. It may have been earlier years. I forget. However one of our RDs the compressor would cycle on and off and that cold air would be lost later in the day and I replaced the high pressure switch and issue was fixed. 

[Joey Mack]

So my guess is that there is no water dripping from the drain tray, on to the ground??  You say the evap. core is clean and the filter is good? What is the history on repairs to the A/C sys.?  Do you need a new expansion valve?  is the Dryer saturated?  it should have a sight glass on it to check condition...   Now....  If this is a R1234y, lgbtq+ sytem,,, I may have wasted our time...   jojo

[Dirtymilkman]

Warranty? 

[Joey Mack]

warranty would be great, but I think its 1 year on non-driveline parts.  now if an extended warranty was purchased, that may help, but 3 years is a lifetime with this new junk, and Volvo, wont pay for it.  jojo

[wmattharris]

As I stated the truck has less than 60,000 miles and the system has never been opened. Mack standard warranty is only one year from date of purchase and I am outside of that now. I was thinking of starting with the high pressure switch just wanted to hear someone else say it too. I did however notice the lights on the climate control panel were hit or miss making me think that should be my next point of interest. Thanks guys!  

[Joey Mack]

I read the original post again.  I was curious about the evap core freezing up if it is not draining good. A faulty pressure switch is highly possible. On some earlier Mack/Volvo's, I have gotten stumped by a bad compressor, because I wasnt familiar with the internal clutch type compressor. I replaced a control panel because I thought all issues pointed towards it, I was wrong.  I guess I would do a pressure switch..  good chance its a simple issue, since you said the system has never been opened up..  keep in touch,, jojo

[Z.JonesMack]

Check the A/C control unit in the dash. Make sure the wiring harness isn't burning up. This has been a common issue since the R model.