Dometic Penguin II - cools, but compressor cuts on and off

[kmb1966]

I have a 4 year old Dometic Penguin II air conditioner (non-heatpump unit) as the rear unit in a 2003 Newmar Dutchstar that is acting strange.
The unit in Fan Auto mode comes on when the thermostat is set below the set point as expected. But it will cut off (fan and compressor) briefly (5 seconds) and it has not yet reached the setpoint temp. Then it will come back on and continue to cool again. This unit has been doing this for several weeks while we have been on vacation. But now the unit is doing something slightly different now. It will come on, cool (45-49 degrees coming out of vents, 68-69 degrees on the intake vents) but will only cool for approximately 7-10 minutes and then the compressor cuts off, fan continues to run. Then the fan will continue to run for approx 10 minutes without compressor. Compressor will kick on and only run 3-5 minutes, and then cutoff again. This operating cycle continues until it eventually reaches the setpoint temp and finally the fan and compressor will turn off. This causes it to take a long time to cool off, and at times we will wake up hot in the middle of the night to find the fan on, but the compressor is not, and yet it has not reached the setpoint temp. In the Fan ON mode, basically the same thing happens. The unit will come on and cool, but then after 10 minutes or so the compressor disengages and only the fan runs but the setpoint temp has not yet been reached . I don't think this is normal behavior and I am unsure what the problem is.

[philh]

Check the seal between return air and cold air.

Make sure thermocouple is in hot air flow

[Chris_Bryant]

I don’t have my temperature/pressure charts, but iirc, with an outside temperature at 80 or below, the evaporator coil temp will be below freezing, so the freeze sensor is working as intended.

[DFord]

There could be a freezestat stuck between the coils of the evaporator causing this issue. And the capacitors are another possibility.

The freezestat prevents the indoor coil from frosting over and completely stopping the flow of air through the coil. When the compressor stops with the fan running, the ice melts and compressor restarts only to have the coil freeze up again.

If it's a capacitor, the internal overload on the compressor could be overheating and breaking the power for the motor until it cools.

[kmb1966]

marcsbigfoot20b27 wrote:
Wait, 68-69 on the intake vents??????

How cold are you wanting the inside of your rig?
What is the thermostat set at?

During the day I have it set to 75
At night I have it set to 70

The readings are from a laser thermometer, so that it was it reads IN and OUT.

[marcsbigfoot20b]

Wait, 68-69 on the intake vents??????

How cold are you wanting the inside of your rig?
What is the thermostat set at?

[kmb1966]

marcsbigfoot20b27 wrote:
I would bet it is freezing up/freeze sensor. Is the fan on high? How much humidity?

I'm not sure if this is what you are asking, but when I put the fan in the ON-HIGH position, the compressor and fan come on, unit cools for approx 7-10 minutes, then the compressor goes off and fan stays ON. Then after about 10 minutes, the compressor will come back on for about 5 minutes, then goes back off. This keeps on going this way until the setpoint temp has been reached.
Today outside temp is 80 degrees, humidity is 85%.

[Roger10378]

marcsbigfoot20b27 wrote:
I would bet it is freezing up/freeze sensor. Is the fan on high? How much humidity?

X2

[Chris_Bryant]

Have you been on the roof to check it out? A hole in the shroud will cause that, allowing air to bypass the condenser. For this problem it would cycle on the overload.

[marcsbigfoot20b]

I would bet it is freezing up/freeze sensor. Is the fan on high? How much humidity?

[Ranger_Smith]

Sounds like a capacitor going bad. I just had one that did the same thing. Compressor would cut off then come back on. Replaced run capn and no more issues.