Mariner Posted December 31, 2015 Report Share Posted December 31, 2015 Just had a new rear rooftop Dometic heat pump installed. It seems to be cycling on and off on the A.C setting too fast. The fan comes on, then the compressor kicks in as it should, but will shut off again in less than 10-15sec. After the usual 2 min. wait it will kick back on, and then run for a short while before it again kicks off. This can't be normal, our old one never did that. Is there a setting somewhere that sets the temperature range for starting and stopping? Link to comment Share on other sites More sharing options...
SCClockDr Posted December 31, 2015 Report Share Posted December 31, 2015 Are you able to observe the current draw during its brief run? What happens to your line voltage? If those appear normal I predict a HVAC tech in your future. My limited experience would lead me to look at the run relay not staying latched. Link to comment Share on other sites More sharing options...
Kirk W Posted December 31, 2015 Report Share Posted December 31, 2015 A run of 10-15 seconds is not enough to have any effect upon temperatures so there is clearly something wrong. You need to get the installer back to make this right. Link to comment Share on other sites More sharing options...
Wrknrvr Posted December 31, 2015 Report Share Posted December 31, 2015 There is a PTCR on top off the start capacitor that is most likely bad. A PCTR is a positive coefficient thermal resistor. There are not available separately, but can be obtained from Dometic in a start capacitor kit. The PCTR is either a little black square thing on top of the smaller capacitor, or is inline and looks like a small beer keg with terminals on it. That is a good thing to look for first and easy. There could be something else but that is the easiest to do. Since it is new warranty will cover it. Safe travels, Vern Link to comment Share on other sites More sharing options...
Mariner Posted December 31, 2015 Author Report Share Posted December 31, 2015 I don't believe voltage is the problem since the front one works fine. I had a call into Dometic, but they're closed for New Years. I'll be calling the installers here in Myrtle Beach Mon. I just thought maybe, just maybe there would be a simple fix. How naive of me. Link to comment Share on other sites More sharing options...
Kirk W Posted December 31, 2015 Report Share Posted December 31, 2015 If it worked right before the service call, but doesn't work right now........................... I hate to point a finger but when I was in service work I always considered that to be a hint that I might have caused the problem. Link to comment Share on other sites More sharing options...
Bill Joyce Posted December 31, 2015 Report Share Posted December 31, 2015 If you have an old 4 or 5 button thermostat, you can't just put in a new Dometic unit. You have to put in a retro-fit control board on the heat pump to make it work, which is the same board on your old heat pump. You can't go to the new thermostat unit with a ducted unit without changing all air conditioners and heat pumps, since they are incompatible. Link to comment Share on other sites More sharing options...
Mariner Posted January 1, 2016 Author Report Share Posted January 1, 2016 If you have an old 4 or 5 button thermostat, you can't just put in a new Dometic unit. You have to put in a retro-fit control board on the heat pump to make it work, which is the same board on your old heat pump. You can't go to the new thermostat unit with a ducted unit without changing all air conditioners and heat pumps, since they are incompatible. I have the 5 button thermostat, and they did put in a new control board. It's just weird that it cycles on & off so quickly. That can't be good for a compressor. Link to comment Share on other sites More sharing options...
Kirk W Posted January 1, 2016 Report Share Posted January 1, 2016 It's just weird that it cycles on & off so quickly. That can't be good for a compressor. That is not good for the compressor. Link to comment Share on other sites More sharing options...
Mariner Posted January 3, 2016 Author Report Share Posted January 3, 2016 To add to my confusion, now that's it's cooled off, I've started using the heat pump. It cycles on & off like it should, unlike the A/C. I'll be calling Dometic tomorrow to get an idea of what's going on. In the meantime, any ideas why one would work properly while the other doesn't?? Link to comment Share on other sites More sharing options...
Kirk W Posted January 3, 2016 Report Share Posted January 3, 2016 As a former service tech, I think that there is a problem in the install, probably with the controls. But this really isn't my field of expertise so I'll admit that I don't know enough about how the controls work to be able to analyze it, but am analyzing the symptoms and their timing. Link to comment Share on other sites More sharing options...
Wrknrvr Posted January 4, 2016 Report Share Posted January 4, 2016 You do need to call Dometic. My thoughts are they have the middle speed wire connected. If I am correct that is what is wrong as it will cause weird problems. But then the heat pump works. If you do not get Dometic then pm me and I will give you there number. Safe Travels, Vern Link to comment Share on other sites More sharing options...
Mariner Posted January 5, 2016 Author Report Share Posted January 5, 2016 Dometic was at a loss as to what's going on. And this morning the heat pump isn't coming on at all. Thankfully the RV tech who installed it is coming out this afternoon. So hopefully he can find a solution. Link to comment Share on other sites More sharing options...
Kirk W Posted January 5, 2016 Report Share Posted January 5, 2016 Keep us posted. Link to comment Share on other sites More sharing options...
Mariner Posted January 6, 2016 Author Report Share Posted January 6, 2016 This drives me crazy!! Of course when the RV tech came yesterday everything worked fine. And this morning the heat pump is pouring out warm air. It's enough to make me pull out what hair I have left. I have a buyer for the coach and want to make sure EVERYTHING works properly before I turn it over to him. Intermittent problems have been a pain for me as long as I can remember. Link to comment Share on other sites More sharing options...
oscarvan Posted January 6, 2016 Report Share Posted January 6, 2016 HVAC is not my top skill, but mine does that occasionally too, always has, and I was told it is a defrost cycle? Link to comment Share on other sites More sharing options...
fairway2002 Posted January 6, 2016 Report Share Posted January 6, 2016 Hello Do you have a power distribution system? They can shut down the unit (compressor) but keep blower running. Link to comment Share on other sites More sharing options...
Mariner Posted January 7, 2016 Author Report Share Posted January 7, 2016 Everything is still working properly now...geesh!! There is a temp sensor on the heat pump that won't let it come on if it's too cold, but I knew that. It's just that the other day it wouldn't do anything and it was 40 degrees. But now, all is right with the world. All the tech could do was check it all out & then shrug his shoulders. I know the guy and he's meticulous, and I trust him, so we'll wait & see how it goes. Link to comment Share on other sites More sharing options...
Ronbo Posted January 7, 2016 Report Share Posted January 7, 2016 It will reverse the freon and blow warm air in the summer and cold air in the winter to melt the ice on the coils. There is a temperature sensor that controls this, Link to comment Share on other sites More sharing options...
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