2017 Thor Compass a/c works on generator but not 30 amp

[Major_Dad]

We downsized from a 34' TT to this little MH due to my disability, and to make travel easier. The 13.5 a/c works great on the propane generator, but shuts down when the compressor tries to kick in. The manual says nothing about this. A trusted technician tested the power outlet on the house and the 30 amp cord, and the problem isn't there. Anybody have an idea what I'm missing?

[j-d]

MD - Glad you've got it!

Bryan's not only got you running! With this knowledge you'll make sure the twist lock is FULLY seated, EVERY time, and that'll keep you from having early failure in those contacts.

[Major_Dad]

carringb wrote:
Also if you have a twist-lock cord on the mothorhome, make sure its it is actually turned after the cord is inserted, before tightening the retainer ring. Otherwise the twist lock contacts won't have proper engagement.

We have a winner! Since I've lost most of the use of my hands I have not been the one connecting the electricity. There is a slight clockwise twist to secure the power supply cable to the RV. My brother-in-law twisted it in for me and connected the power cable to a 20 amp outlet at the RV barn. It ran for 15 minutes beautifully. I am still taking it to my RV repair shop to get a Maxxair cover and a black tank flush installed. But the mystery of the air conditioner that works on generator but not shore power has been solved.

Many thanks to all of you who offered your expertise to get this poor old disabled vet back on the road!

[Major_Dad]

KAttkisson wrote:
please inform us what is found as this is intriguing. Thanks

WILCO. And I won't do anything unsafe. Heading to trusted RV repair shop next week, then to nearest Thor dealer in New Braunfels if necessary.

[KAttkisson]

please inform us what is found as this is intriguing. Thanks

[Bordercollie]

Find all GFI 110vac outlets and press reset buttons. Go to power panel and open and close all circuit breakers. Look at shore power plug, check for loose wires. If none of these are the culprit, find an RV repair place that does RV 110vac troubleshooting and repairs or an electrician. Don't risk your life.

[Major_Dad]

Thanks for all the responses. The a/c works on the propane generator but not 30 amp. Both the 30 amp outlet and the 30 amp cord from the outlet to the rv test out fine. There are no appliances on at the same time except the refrigerator and some lcd lights. We haven't tried the on-demand water heater yet. I will double check the twist connection, though we've had that on the previous two rvs with no problems. Guess I call Thor tomorrow.

[tatest]

Could be low voltage, it has to be tested under conditions that represent the problem load.

I plug an AC voltmeter into one of my interior outlets, monitor readings under various loads. While it is not the same circuit as the air conditioner, it provides a good clue as to what is going on between the breaker box and the power source (measuring at the source usually just tells me no-load voltage).

I want to see at least 108 V inside when running the high loads (nominal is 120 V), no more than 132 V with no load. I also want to see only a small drop from post to inside under load, as large voltage drop suggests a high-resistance connection somewhere: socket or plug, cord connections at junction box, connections inside breaker box, too much cord too small. Problem connection can be either live or neutral. High resistance connections often don't show up with no-load voltage readings, or even light loads.

[KAttkisson]

I'm a little confused. I think you are saying that the compressor won't start on either shore power or generator? If this is correct you probably have a bad start capacitor allowing the internal overload to trip.

If it will run on the generator and not on shore power everything else being brought up in replies need to be investigated.

[carringb]

Also if you have a twist-lock cord on the mothorhome, make sure its it is actually turned after the cord is inserted, before tightening the retainer ring. Otherwise the twist lock contacts won't have proper engagement.

[D_E_Bishop]

Major DAD, It seems you have ruled out the usual suspects and as noted the problem is perplexing as it is the opposite of the normal complaint.

I am not HVAC knowledgeable, so I am assuming that the AC unit does not have a auto reset CB on the circuit from the panel to the unit and that is none inside the unit, so that leaves the line from the shoreline connection to the output of the transfer switch. That of course is assuming there is a transfer switch.

If you have a shoreline that has to be disconnected from the 30 amp outlet and connected to an outlet in the service bay, then the wiring from that outlet to the CB panel needs to be tested.

There is a guy on here that has Golden in his forum user name who is a really knowledgeable HVAC guy, in fact it is/was his profession. Try searching for him. Also Chris Bryant is an outstanding source of knowledge.

Good luck with your problem and sorry to read about the reason you downsized. It just so happens that we are doing the same thing for the same reasons.

[ron_dittmer]

carringb wrote:
I actually run my A/C off a 15 amp circuit no problem

Actually I am right with you on this. My a/c runs off 15 amp service just fine at home. I was only trying to rule out the possibility given we are not familiar with his particular rig.

Then there is the unknown condition of the power being provided where he is staying....hence your comment about measuring voltage.
Right On carringb. His problem might go away when staying somewhere else, maybe as simple as changing campsites to one closer to the campground power source.

[carringb]

X2 on making sure other electrical is off, such as electric water heating. I had a mystery draw that turned out to be a water hot pot that had been accidentally switched on!

30 amp circuit should run that just fine. I actually run my A/C off a 15amp circuit no problem. If 30 won't start it, you should monitor voltage in the coach when it tries to start, and see if its dropping below 110 volts during startup.

[ron_dittmer]

j-d is onto something. You were not clear that you have the following condition. Make sure you use a 30A power cord all the way to the campsite power box. If it is too short, use a 30A extension cord. Do NOT convert to a 20A cord. Menards sells 25 foot long 30A extension cords cheap. Even with a 30A extension cord, it can become questionable with certain rigs.

Another culprit could be your power transfer switch, assumed you have one. It could be faulty.

One more thought. Is there any other appliance in the motor home that could be turned to the "on" position? Something like a simple hair drier plugged into a shore-power-only outlet will rob the power to the a/c unit stealing the thunder it takes to get it going.

You do have a 2017 model. I assume you are under warranty. I would call the RV manufacture Thor Industries. Hopefully they can offer you some trouble-shooting tips while you are on your trip, rather than saying to take it in at your next opportunity.

BTW: I see Thor installed a 68 pound, 16 gallon propane tank inside that diesel Transit. Unless special ordered with a diesel generator, Sprinter & Transit diesels generally come with a propane generator. Nice to see you have great reserves.

Our 40 pound, 10 gallon propane tank serves us very well, but it supports only the fridge, stove, hot water tank and furnace. We have a gasoline generator utilizing a 55 gallon E350 fuel tank.

[j-d]

First, must say that your case is the opposite of just about all others. Usually, A/C will start on 30A shore tie and it's the owner's generator that won't start it.

It seems to me that your household power outlet is deficient somewhere. You could have a 30A receptacle connected to a 30A branch circuit in a fully good 200A power center in the house. But if the connecting WIRE isn't rated for 30A (too small a wire gauge), your A/C will not be able to draw the power it needs.

Likewise, if your outlet is OK but you extend the RV's shore tie cable with a light duty extension cord, the A/C's starting demand won't be met.

Look at it this way: Your garden hose and the city water main out in the street might measure 75-PSI water pressure. That does NOT mean your hose can deliver anywhere near the gallonage that the main can. You can have voltage, but that doesn't mean you're going to get the amperage you need.

Do you have an AC (alternating current) voltmeter that you can set up in the coach and see what happens to voltage when you try to start A/C on shore tie? My guess is it's going to take a nosedive.