Air Conditioner does not cool

First, Congratulations on your Progress! Speaking just for me, an A/C is worth working on if it's not a problem with sealed system such as failed compressor or leaking lines and coils. Worth it to replace things like fan motor(s), capacitor(s) etc.

This snippet from Doug's reply above gives you a way to do a ballpark check on compressor performance.

dougrainer wrote:
IF you have the Intellitec EMS system on your RV. Turn the Genset ON. Let genset run for 30 minutes. Turn OFF all 120 appliances. Then turn on the Rear AC to HI COOL. Watch the AMP draw meter on the Intellitec remote display. IF the amp draw is NOT over 10 amps but close to 5 to 7 amps, your unit is out of Freon. If the display shows 1 to 4 amps, the compressor has not started or running. Doug

If that compressor is running at 11 Amps, you may be back to good again. With it running, if you can reach in safely, the smaller line from the compressor should be warm to hot to the touch, and the larger one should be cool to cold. Those are your Discharge and Suction lines, respectively.

Chris Bryant, one of our other techs, has a blog post on how to do an cleaning on your rooftop A/C. Very useful and not hard to do. Right now his site/blog seems to be down. Basically, if you remove the shrouding that's under the beauty cover, clean the indoor coil and the drain pan. The outdoor coil and its fan are accessible as soon as you remove the beauty cover aka Shroud. I found it worthwhile to clean the indoor blower wheel, but that requires quite a little more dismantling. Chris didn't include that in his blog post.

Final update: I replaced both condensers and the AC compressor now seems to come on and draw about 11 amps. Before only the fan was coming on drawing approx 5 amps. We'll see how good it actually cools when it finally gets hot out. One note is that I replaced both condensers so I don't know which one was actually bad. Physically both condensers looked like new. Thanks very much to all who replied to my post with the tips and suggestions.

I have seen the outside coils (Condenser in Cool mode) get so clogged they failed to cool the refrigerant,, In my case when this happened the system pressure went UP UP UP the compressor current went UP UP CLICK (sound of circuit breaker tripping) and a good cleaning fixed it all.

However there are other causes as well. Both of my Factgory units have had to be replaced.

I have been following this thread because I am having the same issues. The run capacitor on ours is 10/45 microfarads. It tested well too but I was still getting no power to the compressor. I removed the "big box" inside and tapped around on the relays and reseated the sensors and thermostat wires etc.

The compressor then came on. It is only about 62* ambient here today so will wait for some warm weather to really know if it is going to work. One thing I did notice is that when the fan is running it draws 3 amps. With the compressor it was about 10 amps measured through the PI power monitor system.

Hope this may help.

There'll be two MicroFarad values on the two-way RUN capacitor. An Appliance Parts or A/C repair Store should be able to provide it. As I said, you can buy just the HERM side, two single capacitors, or even one with the correct HERM value and a different FAN value and connect with a jumper to make them work together.

What are the two MicroFarad, may say uF, values? If Voltage is marked 370, a capacitor with the right uF and 440 volts will work.

Thanks to j-d I found and ordered what I needed. I post an update if it fixed the AC. Likely in a couple of weeks.

Thanks j-d that looks exactly like what I have. The smaller one was easy to find an exact replacement, the metal one I haven't been able to find yet

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.

Looked at it more in depth today, took the cover off the AC unit. 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.

Not sure what's going on but unable to post since 9AM... came in through trailer life and finally able to post. As usual Doug has good advice.

Trying to use it when it was cold did not hurt it. I have much the same system and use my heat pumps down to 30° without problem. With the fan in the auto position and trying to cool can you hear the compressor start shortly after the fan comes on? If you can monitor your AC amps, is there a 10+ amp jump after the fan comes on indicating the compressor is running? Hopefully not as the fix will be expensive.

The most common cause of the compressor not starting is a bad start capacitor located in a metal box on the side of the unit. It is the larger of the two and costs $20... worth carrying one as a spare.

Let us know if the compressor is starting or not.