Thanks Denny,
We removed the filter grid and checked temps as the air entered the evaporator coil fins. Our Air Distribution Box has an option to open and direct air flow from the blower immediately below the unit before going into the duct work. That’s where we measured cold side air. Our check points were close to the warm air return and the cold air out as you can get.
We used a magnetic mount digital thermometer to allow the thermometer to stay in place as long as necessary to get stable measurements.
We replaced the control box and thermostat because on last camping trip the unit had repeatedly failed to restart after room temp has exceeded set point by 10 degrees or more. (We’d leave the camper early in the morning while outside and inside temps were around 67 and set the ac to auto at 72 degrees. When we retuned late afternoon (outside temps around 82), the air temp inside the camper was around 84 and the ac had never cut on)
In those cases I had to switch the ac to off, reset CT thermostat to - -, then reset to auto ac at 72 degrees. Then the unit would immediately cut on, cool to the set point, drop from high to low and then shut off as normal. However it would not start back up unless I reset as described above. I replaced the CT thermostat but that did not help. So we replaced the control box in hopes it would solve that problem
After we replaced the control box and with a new CT thermostat we rechecked the air temps and there was no difference from the temps we checked initially. The tech then said it indicted low charge and recommended replacing the AC.
Perhaps you can tell me, why don’t they use R134 in these units.