Bedroom AC stopped working

[farmer_boots]

My bedroom AC stopped working. The Fan runs but you can hear the compressor start for a second or so and then turn off. It draws about 60 amps and then drops back to about 5. This cycle just keeps repeating until the unit is turned off.

Yesterday I removed the cover from the top unit and found a capacitor burned and a resistive device burned. Looking at the circuit it looks like the start capacitor and some king of thermal resistor.

I checked the capacitor and found it was shorted. I guess that's what took out the resistive device. It looks like there is some type of thermal protective device that detects when the compressor is getting hot and shuts off power. That's what I assume may have save the compressor, I hope.

Anyone recognize what I am talking about? Should I just replace this capacitor and resistor or should I replace the run capacitor as well? Or are there other things I should replace?

[DaveG39]

Mine did the same thing and it turned out to be thee compressor seized and needed a new air conditioner.

[farmer_boots]

Received my parts Thursday and installed them Friday. Like most everything that appears to be simple there is always a twist that makes it more difficult. The wires were burned badly so I was having a little difficulty identifying them. The schematic shows the heat pump reverser valve connected to the HERM circuit (start winding). Did not think that was correct so I thought I would take a look at the other AC unit. This unit has been acting kind of goofy. Just before it turns off you can hear the fan speed increase. When I opened the electrical junction box in the upper unit I found out why, the same capacitor had come apart and the OPTCR fell apart in my hand. I am assuming it performed enough for the compressor to start but leaked enough current it affected the fan speed. I have noticed in the past circuit the AC circuit breakers would trip for no apparent reason. I guess there was a reason. So for a while I had no AC, got the bedroom up and running and then called around and found a generic capacitor with an OPTCR on it. Installed it in the front unit and now we have two AC units again.

Next time I notice goofy fan speeds or circuit breakers tripping for no apparent reason, I will check these capacitors.

P.S. When the compressors first turn on the total current draw is nominally about 11 amps. After a few minutes (I assume compressor head pressure increasing) it settles out at nominally 15 amps. I assume this is normal?


More lessons learned, now if I could just remember them, what were we talking about?

[sailor_lou]

It sounds like you are referring to the PTCR. From the Dometic service manual:

C5. PTCR Device or Start Relay

The positive temperature coefficient resistor, or PTCR has
replaced the compressor start relay and the start capacitor
on some models. It should be checked in two different ways:

First check continuity. Turn the air conditioner circuit breaker
to OFF. Disconnect the PTCR from the circuit. Check for
continuity. If there is no continuity, replace PTCR.

NOTE: This is an energized circuit. Shock can occur
if not tested properly. Testing to be done by a
qualified service technician.

The second check to take is an amperage reading. Clamp
an ammeter around the wire from the PTCR to the capacitor.
Turn the air conditioner circuit breaker to ON and start
the air conditioner. When the compressor starts, there will
be an amperage reading for approximately one second or
less. If there is no reading, or if there is a prolonged reading,
the PTCR or start relay is faulty and must be replaced.


Lou
05 Travel Supreme Envoy

[joeprinter]

Easy fix you need one of these...http://s888.photobucket.com/user/joeprinter/media/hardstart.jpg.html?sort=3&o=1

easy to find on ebay