Joe Lee

If you have an Automatic Transfer Switch, and it is misbehaving, it could be making the ‘thud’ sound. Perhaps place your hand on the case of the ATS and see if you can feel it.

Great project! I really need to follow your lead. I appreciate your willingness to document this for all of us.

Hello all! I have been in search of a replacement switch for the electric element side of my Aquahot for some time. Called Eaton and they don’t have a replacement. Any suggestions? Thanks! Joe

I don’t know where to take an amp reading to determine my charge state. Could you please advise? I do have a multimeter with an AC 400 amp clamp.

Ok, smart people! Please let me know what you think about this. I have discovered that the 3 copper tubes as shown in the attached picture (2 in the foreground and 1 behind and they are marked with silver foil tape) are not nearly as cold as the same copper tubes on my other a/c unit as I’m running the unit in cooling mode. what does this mean? Thanks! Joe

Thanks Tom! Here’s where I’m at: 1) I did replace the filter with a new appropriate filter material. 2) I have inspected both units. I didn’t see anything that looked out of place and both units looks alike. 3) My first step was to clean both units with a coil cleaner recommended for RV A/C units. No change and they didn’t see too dirty. My Rig spent the first 18 years of its life inside. 4) I have the install manual and I believe I have completed those steps. 5) Your next idea is to call Lippert. I did call Dometic. Would Lipper be a better source? As I’m not a pro so, Dometic wasn’t very helpful. Today, I replaced the PTCR (Postive coefficient thermal resistor). My short cycle times changed from the compressor being on for 50 seconds to about 5 mins. Progress but must not be the solution. Thanks for the heads-up on the front unit being in trouble as well since the Delta T is too great. Seems it may be time to give up on the repairs unless a call to Lippert or a professional will help. What do y’all think? Thinking of adding a Remote Thermostat to the Rear Unit that is short cycling. This would eliminate the thermostat at the main thermostat unit on the wall. Also, thinking of replacing the thermostat and control board next. Thoughts if this is a waste of time and money? At least isn’t getting cooler in Amarillo TX! Hoping to be out of here in the next month.

My thanks to everyone for sharing their time and expertise. Well, within a day, my Dometic Penguin started short cycling again. The compressor will only stay on in ‘Cool’ mode for about 50 seconds. However, the ‘heat pump’ mode works very well. I’m going to retest all the components and use the advice already given. Here’s a few details on running the unit in Heat Pump mode: I ran my Penguin for over 60 mins and, using my Pocket Thermometer (thanks Tom!), I’m showing a temperature Delta T of 35 degrees F. Intake temp = 92. Return temp = 127. Man - it’s hot in my bedroom! The compressor remained on for the entire test for over 60 mins. The unit didn’t Short Cycle a single time. Does the Heat Pump working well suggest anything else I should test/replace? And, don’t all the components work the same way, just reversed to create heat or cold? Is there a way to test to Control Board? Thanks for all the help!

Well Folks - I can’t believe the solution for my A/C short cycling. I removed the filter material I was using and the short cycling stopped. Kinda embarrassed to share my solution, but perhaps it’ll help somebody else one day. This filter material was about 1 inch thick. I just order some that is only 1/4 inch thick. Seems to have helped. My A/C unit is now cycling about 3 times an hour. The temperature has not cooled down to the temperature that I have set on the thermostat, but this may be normal. Bottom line: the compressor will stay on for about 20-25 mins, then cycle off for about 4 mins, the turn back on. It’s not freezing up, so I can’t determine why it’s cycling. But I’m much better off!

Hey Gary! Thanks for sharing your time with me. I did test the thermal overload with and without the compressor running. Both situations test positive for continuity. I also swapped out the thermal overload between my front and rear a/c’s. No change in my short cycle problem. I’m done fighting today. Thanks for all the support! Joe

Thanks for the idea! I have attached what I believe is the Thermal Overload. If this is the correct part, I did test it for continuity and it did have continuity. So, could it still be bad?

Question for someone what knows freeze sensors. I measured the ohms for my rear freeze sensor and I got a reading of 22k. The local RV shop thought it should be 32k. Both my front and rear freeze sensors measured about 22k. So, I’m thinking these are good. I’m needing an expert to weigh in. could this cause the short cycling issue? If so, I’m just going to buy 2 new ones!

Hi Gary - the short cycle lasts for about one minute. I have tried the fan in auto, high and low to see if there was a difference. No change. The compressor constantly short cycles at about 1 min. The only time I found the short cycle to change was after I ran the heat pump for about 10 mins. After that heat pump cycle, the A/C did stay on for about 8 mins. Then, it was back to the 1 min short cycle.

Hi! I’m still struggling to figure out my Dometic penguin rear AC that is short cycling. Today I tested the capacitors. My run capacitor is a 20+10. (If I’m reading it correctly!). The 20 side is reading at 18.6 2,10 side is reading at 10.29. Could someone help me determine if this capacitor is good with these readings? And, could this capacitor have any impact on the short cycling? Thanks everyone and happy Friday!

Hi Coach J - wow. Hoped I had found a problem. It does sound like the opposite of what you had. Hoping I had found a simple fix. My continued thanks for this group! I will continue the hunt for the short cycle problem.

Hello All! I have been using this topic to help me diagnose my A/C problem. Thanks to all for documenting this so well! My issue is with my rear Dometic Penguin (2002). The unit is ‘short cycling’. I have been using the attached Troubleshooting Guide and discovered what I believe is a missing Remote Temperature Sensor. It is WHITE as shown in the Guide. When I traced the wire from the control board to the sensor, I discovered that the sensor was missing. See Picture. It would appear someone in the past removed this sensor on purpose. The 5 button thermostat control is located in the bedroom. Would anyone know if this sensor is required? Seems like it! Could this missing sensor cause the ‘short cycling’ problem? My front A/C unit has this sensor and it is working properly. Thanks for your thoughts!