Air Conditioning Issue

[chuckbear]

Any air conditioner techs out there or owners that have had the same problem? The front roof AC has been working fine. Today when I turned it on, the compressor keeps turning on and off and the unit never starts blowing cool air. It has only run on the generator, I don't have a 30 amp outlet to plug into, and it will eventually shut down the generator. The rear unit is working fine. Chuck

[dougrainer]

NeverHome2 wrote:
It could also be low on refrigerant and cycling on the low pressure switch. The pressure rises with temperature but as soon as the compressor starts it starves for gas and sucks the pressure down, opening the low pressure switch and shutting down the compressor. You will need to put a set of refrigeration gauges on to verify this. The gauges are also needed to put refrigerant into the unit. Caution though, if it is low on gas there must be a leak which must be repaired. Look for areas of oil leakage they will show where the leak is.

RV Roof AC units have no low pressure switches. Doug

[Bill72927]

Sounds to me like the fan motor is not running? Might be a "mud dauber" nest preventing the fan from rotating, or maybe a failed run capacitor. Good luck with the problem!

[rgatijnet1]

Do you have an Energy Management System? This EMS also regulates power to the various AC units so as prevent two units from overloading the available current.
To check the output of your thermostat you will have to pull of the bottom cover on the AC unit and you will see a box that usually has all of the wires coming in to the unit. With a volt meter you can measure if the AC 120 volts is being switched off and on by the EMS, and with the meter set on the DC voltage scale, you can tell if the voltage coming from the thermostat is switching the unit off and on.

[chuckbear]

rgatijnet1 wrote:
It could be getting a faulty message from your thermostat that is cycling the AC unit off and on. AC units have a built in time delay so that the compressor itself is protected from on-off operation. If you interrupt the power to either one of your AC units, the compressor will not start running until after this protective time delay. You need to check to see if the thermostat is calling for it to run continuously or if it is getting faulty info.

And just how would one check that? Chuck

[rgatijnet1]

It could be getting a faulty message from your thermostat that is cycling the AC unit off and on. AC units have a built in time delay so that the compressor itself is protected from on-off operation. If you interrupt the power to either one of your AC units, the compressor will not start running until after this protective time delay. You need to check to see if the thermostat is calling for it to run continuously or if it is getting faulty info.

[NeverHome2]

It could also be low on refrigerant and cycling on the low pressure switch. The pressure rises with temperature but as soon as the compressor starts it starves for gas and sucks the pressure down, opening the low pressure switch and shutting down the compressor. You will need to put a set of refrigeration gauges on to verify this. The gauges are also needed to put refrigerant into the unit. Caution though, if it is low on gas there must be a leak which must be repaired. Look for areas of oil leakage they will show where the leak is.

[dougrainer]

EMS, not ECM system. IF the compressor is indeed turning ON and then turning OFF, then the capacitor is not the problem. The problem is probably a bad compressor and the compressor overload is kicking it out. But, a Capacitor is a cheap quick attempt without having the proper tools for a correct diagnosis. Does your EMS have an AMP readout? If so, watch the amp readout when the compressor starts and then kicks out. That will tell you what the amp draw is on the compressor after start up and it is running for that few seconds. IF it starts and runs for a few seconds and the amp draw is higher than 15 amps(amp draw added with other amp draws), the compressor is bad.
You look at the EMS readout with the ac off and lets say it reads 17 amps. You start the AC and you will see a 3 amp added for the fan motor-- now you show 20 amps. When the compressor kicks on you will see a spike above 50 for a millisecond, as the start capacitor kicks it on. Then, IF the amp reading is over 33 to 35 amps when the compressor is on and then slowly rises, then your compressor is bad. Doug

[chuckbear]

The units are controlled by an ECM for both units inside the coach. I can run either separately and the rear unit runs just fine by itself. It's only the front unit that has the problem. The rear AC and the generator play very happy together. I'll take a look at the start capacitor tomorrow. As soon as I figure out how to get the covers off. Thanks for the link to the troubleshooting manual. It was working just fine a couple of days ago. Chuck

[MountainAir05]

here is a manual. run the troubleshooting pages.

http://bryantrv.com/docs2/docs/rvp/rvp6789mech.pdf

Do you have a switch to run either the front or rear AC inside the RV, if so switch it the rear one and ensure the generator is working correct. Then run thru the troubleshooting pages. I agree it sounds like the start/run cap.

[bullydogs1]

Sounds like the start capacitor is fried..easy fix...plenty of posts about it if it is a dometic...make sure you ground out the capacitor before you work on it..it is under cover on roof and you will see it probably fried.

[newman_fulltime]

it's a Coleman good chance a hole got rubbed in the tube and its toast.You can get a regular ac guy to fix the hole and recharge it if you want to take that chance

[chuckbear]

newman fulltimer wrote:
is it a Coleman ac?

The manuals that came with the coach say RVP. Chuck

[newman_fulltime]

is it a Coleman ac?