My bus has two A/C rooftop units (they function as heat pumps too) @ 15,000 BTUs each. They are both RV Products model 9024-876. The front unit doesn't cool quite as well as the back unit does. I was up on the roof yesterday and took off the cover to the evaporator coil and cleaned only a small amount of dust from it. Also perked up all the aluminum tape to ensure no air leaks were diluting the cool air. Everything else I could see looked fine visually. I keep the units covered in the winter months so the guts are pretty clean. My cleaning and taping efforts failed to facilitate any improvements. I measured the exhaust air temperature of the back unit @ 40F and the front unit @ 52F. Outside air temps were 80F at the time I took measurements.

I decided to take a look inside the electrical box just to be complete. Here is a Slide Show of what I saw. Lots of burned parts.

RV Products makes a hard start kit that includes a starting capacitor and PTCR (Positive Temperature Coefficient Resistor) switch. It's a bit pricey at $44 but I didn't have time to run down the PTCR part. It was burned beyond recognition.

Grainger sells the capacitors and I've included the part numbers below:

2MDV6 - Fan run capacitor (7.5 mfd @ 370 VAC)
2MEC9 - Compressor run capacitor (30 mfd @ 370 VAC)
2MER8 - Compressor start capacitor (88-108 mfd @ 165 VAC)

If anyone knows the part number for the PTCR and a generic source please let me know.

I replaced all the capacitors and the PTCR and the unit is now running fine. Best I could do on the cool air temperature was 48F.
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