Air Conditioner does not cool

wtmtnhiker wrote:
Compressor does not come on. It looks like the start capacitor is the smaller of the two units at least that's what it says on the capacitor itself.

This is what I found just looking up "Duo Therm Capacitor"

Notice that it's metal. And, the presence of an extra set of terminals, means it combines Compressor Run and Fan Run Capacitors into one "Can."
This is a Start Capacitor

Notice that it is Plastic, and there's usually a little "Device" attached to it. That "Device" takes the Start Capacitor OUT of circuit once the Compressor starts. In this pic, it's the little square box the RED wire is connected to. Think of your car. It has a Battery (Run Capacitor), an Engine (Compressor), and a Starter (Start Capacitor). When your car starts, you release the key so the Starter doesn't keep cranking, but the Engine still needs the Battery.
The FAN uses only a Run Capacitor, or the Run part (probably marked "FAN" on a dual capacitor like I pictured, and it's the lower value of the two chambers. Compressor side is probably marked "HERM" (for the hermetically sealed refrigerant system including compressor) and it's the much higher of the two values. Start connects across Common (probably NOT marked) and HERM.
HERM part of the Run Cap should be tested or replaced with a known good one. You can use a single capacitor in place of one side of a bad combined one, or two singles in place of a combined one, but you need a little jumper wire to connect the two COM terminals.
Many Digital Volt Ohm Meters/DVOM will check Capacitors, but not the cheapest ones. There are threads here about meters that do Capacitance (like A/C troubleshooting here) and Frequency (Generator troubleshooting), AC and DC amperage with a clamping jaw, and still handle ordinary AC and DC Volts, Resistance, etc. The list I just wrote would represent one meter that could do virtually all RV-related electrical testing. $50-100 in stores, less on the WEB.