Dometic DuoTherm A/C Help

Trailer A/C:  2012 Dometic DuoTherm 13.5BTU roof mount, ducted with 3313192 LCD thermostat

Status:  Plugged in to 30 amp service.  When turned on, thermostat displays temp setting, no error codes but fan does not run and a humming sound can be heard (like binding motor).

History:  Purchased trailer (used) in Jan, 2018.  Tested A/C at time of purchase for operation/cooling and while loud, A/C blew cold.  We are the third owners and past maintenance history is unknown.

Recent events:  Two-week trip to two different FL state park campgrounds.  First week/park we were plugged into 30amp service and used the A/C for 2-3 hours each afternoon when temps were in low/mid 90?s.  When turning system on in ?Cool? mode, fan starts up immediately and then the compressor kicks on 10-15 seconds later.  Turned system off each day when outside temps dropped into low 80?s.  No issues.

Second campground for week 2, again plugged into 30amp service:  Turned A/C on and fan started as usual however the compressor did not come on and the thermostat flashed ?E5?.  Thermostat booklet lists E5 as an ?Open Circuit? or ?Out of Range Freeze Sensor? error code.  Booklet also notes that with an E5 error, fan and furnace will function but cooling mode is locked out.  All other electrical items in the trailer operated fine.  Just in case we had bad 30amp service, I plugged into the 50amp recept. (using adapter) and tried the A/C again but received the same E5 code.  Not knowing what else to try I reseated all wiring plugs on the inside of the roof unit and also removed and reseated the thermostat with no change.  About an hour later I tried turning it on again and it operated normally with no E5 code.  Chalked it up to gremlins and enjoyed the afternoon.  Once it cooled down enough outside we turned the system off for the night. 
Day 2:  Afternoon temps into 90?s, turned A/C on.  Fan ran and E5 flashed, no compressor.  Tried cycling on/off numerous times and E5 went away, A/C came on and trailer cooled down.  Turned off for the evening as before. 
Day 3 was more of the same:  E5, cycle through off/on, wait an hour and try again and finally it would work. 
Day 4 was a little different:  Still had a few issues of E5, but then the code went away.  Fan was running but the compressor still didn?t kick on.  After 30 seconds or so (maybe more, maybe less, I didn?t actually time it) I bumped the thermostat temp down to 71 (we had been keeping it at 79) and the compressor finally kicked on and it started blowing cold.  Not wanting to risk it shutting down, I left the temp low and let it run.  After about 3 hours it suddenly turned off.  When trying to get it going again I found that it had shut off because it had tripped the A/C branch circuit breaker.  Turning everything back on got the fan running and an E5 code, with no cooling.  Called it quits for the night.
Day 5:  Wondered if maybe there might be an issue with the wiring at our campsite (since all of the issues were in the afternoon at peak times), I tried turning the system on in the morning while it was still cool out (low 70?s).  No E5.  That afternoon I turned it on and got the dreaded E5 again.  Repeated attempts throughout the afternoon brought nothing but sweat and irritation.  That evening we decided to head for home the next morning.  I was hoping that we might possibly just be victims of weak wiring at our campsite and that maybe the electric load of other campers during peak times might be the issue.

Day 6:  Got home after a long drive and plugged into my dedicated 30amp RV circuit.  Got things unpacked and figured I?d check the A/C.  Turned it on and no E5.  No fan either.  Nothing but a hum like described at the beginning of this post.  It?s been raining since we got back so I haven?t had the opportunity to get on the roof and pull the cover to get the exact model number or do anything further.  Figured I?d check in here to get some opinions/suggestions as to where to start.

So, any suggestions?

UPDATE

After thinking it through some more, I'm leaning more and more towards the idea that we had bad power/low voltage at the last campground, thus triggering the error code and eventually damaging the A/C unit.

This morning I pulled the housing and the capacitor.  After discharging it, I found that while the compressor side would take a charge, the fan side would not.  It also has a slight bulge in the bottom...  Ordered a replacement which should be here Saturday, will update after that.

Also starting my search for some sort of EMS to prevent this from happening again - Any suggestions?

One of these would:

http://www.progressiveindustries.net/

They come in 30 and 50 amp along with either being available as a plug-in or hardwired device.

  I second kdbgoat. Last summer during a hot spell, the tv shut off and all our lights in the house suddenly dimmed about half brightness. It took a second to realize what was going on, but we quickly shut off the air conditioner and I killed the breaker to the deep well pump, (500 feet down, 2 horsepower pump...not cheap to replace) The lights continued to be dim so I went ahead and killed the main breaker to the house. I called my neighbors to see if they had electricity and they said yes, but the lights are dim. I told them they better turn off their heavy use stuff like well pump, etc. Our toy hauler is stored inside the pole barn at th top of the hill and we keep it plugged in all the time, via a progressive surge protector. I went up there to check and the progressive surge protector had tripped and showed 120v on line #1, 30 volts on line #2. Once power was restored, everything in the camper was fine......as well as the house. My other neighbor I couldn?t get ahold up replaced their well pump that week......$3500. Insurance still arguing with utility company over who pays, but so far my neighbor is out $3500. I?m really glad I read this forum and bought one. It was one of my first purchases after we got the camper. There are other brands too, I just went with Progressive because of a lot of positive comments I read on this forum.

Yup, thanks.  Did a bunch of searching and reading about surge protectors and EMS's and ordered my PI EMS-PT30X today.  There's an amazing range of prices on these but the best deal I found was $234.97 (free shipping, no sales tax).  It's already on its way.

New capacitor arrived early so I was able to do the install this morning.  Good and bad:  Fan motor now starts and runs normally (so the cap was bad), but the "E5" error is again flashing.  The trailer is plugged into my dedicated 30amp circuit and voltage is 120.4. 

Next step is to start checking wire connections inside I guess.

Any suggestions welcome...

and hopefully the final update...

I have A/C!  Since everything on the roof looked god, all connections looked good, fan/motor spin freely, etc. I figured it couldn't hurt to do some exploring inside.  So, I took the inside roof panel off and started exploring.  The error code was for either and open circuit or an out of range freeze sensor so I focused on finding said sensor.  Traced it back to the circuit board box and removed and cleaned the plug.  Pressed it back into p[lace, closed up the wiring and switched on the breaker.  Et voila!  Fan started with NO E5 CODE!  About 15 seconds later the compressor kicked on and cold air started blowing.  It's been running for about two hours now, cycling off and on as it should.  I'm going to leave it on all day to make sure that was the fix and not just a coincidence.

Still not sure why the error was intermittent, maybe it had to do with expansion/contraction during the day.  I don't know.  Anyway, the capacitor was bad, the A/C is now working and I have a new EMS on the way.