Ray,

My buses are OTR air buses so my experience is limited to the rare occasions when I have tried to run cruise airs while driving.

It has been my observation (and the basis for my personal requirement for OTR) that cruise airs powered either by inverters or generators are not suitable when driving on very hot pavement. When my OTR was acting up I was forced to resort to using cruise airs while travelling, and with the high outside temperatures they acted exactly as you described. As near as I could determine the problem was they were not getting enough cool air flow over the condensing coils. The heat radiating from the road surface had to have been considerable given that the outside temperatures were in the mid to high nineties.

As soon as the sun went down, the cruise airs went back to functioning as normal because the outside tempertures were coming down.

The cruise airs work fine when sitting in an RV park because the air being pulled into the condensers is ambient. The ground under the coach is not heated by the sun.

This is only an opinion and others who do not have OTR should post their experiences.

BTW, this is a strong justification for roof airs as an alternative to OTR.