AC runs on shore power, quits on gen

[gfourth]

Hi All,

I have a 2013 Jamboree Sport Class C, with a Coleman Mach 15 AC, and an Onan 4000 gen. 30A

Starting last November, while running AC on Generator, the AC would stop after 10 or 15 minutes. When it stops running, the AC is still humming and I can hear the load still applied to generator, but the fan does not spin. It will come back on if I shut off the AC and turn back on a couple times.

The AC runs all day no problem on 30A shore power, did this last weekend.

Things I have done since last Novemeber-
-Replaced both caps
-Added hard start Cap
-Added Amazon Soft Start kit (removed hard start)

One thing I did BEFORE this problem was replace analog thermostat with an Amazon digital one... Could this cause my problem??

Yesterday I checked voltage and freq via a watt killer, with gen running and no load I have a solid 120v 60Hz. With AC running I had 117v 59-60 Hz. With AC and microwave running I had 113v 58Hz.

Does anyone have any suggestions to try? Going on a road trip in 3 weeks, hoping to figure this out!

Thank you

[Jim_HiTek]

Dropping to 113 Vac with both the AC and MW running may not be a fault. Just too much load. I always use to switch off my roof AC when I used the MW with 30 amps. Lessens the strain on a 30 amp setup, everything from the power post to the AC could be harmed. With a 50 amp rig, not a problem.

When was the last time you had done or did maintenance on the generator? Burnished the slip rings, oil, oil filter, air filter? Do that if it's been a while.

Once that's done, then open the generator's control box with the generator off, and check all the wiring connections inside making sure they are tight. With situations where voltage is dropping too much, I always do a tug test of each wire connection...using around 4 lbs of pressure I try to pull the wire out of the connection. The wires should not pull out of course. I also clean up any corrosion and loosen and re-tighten any screwed down terminals.

Then follow the electrical output wiring to the RV wiring. Many times there will be a square electrical box in the generator compartment. Remove the cover and inspect any connections inside. Remove and replace after inspecting any wire nuts or wire connections.

I would of course have held onto the old thermostat unless it was defective...if you did that, put it back in place. I've run into smart thermos that weren't all that smart and did weird things.

After all that, then check out the AC. Note that when the line voltage sags, motors draw more current. The more current causes excess heating, which causes safety thermostats to pop open so things can cool down. So it's always best to try to keep the AC voltage as high as possible when it's running, especially when the sun is beating down on it. So switch it off for those short periods when running high current items, like the MW.

If that fan was damaged by the low voltage sag, it would behave like what you've described.

Come back and fill us in when you solve it...what you found, etc. Good hunting!

[Jkwilson1989]

Number one rule of equipment maintenance is to go back to the last thing you fooled with. I’d swap the old thermostat back in to verify the new thermostat isn’t the problem.

[gfourth]

Originally Posted by Jim_HiTek

Dropping to 113 Vac with both the AC and MW running may not be a fault. Just too much load. I always use to switch off my roof AC when I used the MW with 30 amps. Lessens the strain on a 30 amp setup, everything from the power post to the AC could be harmed. With a 50 amp rig, not a problem.

When was the last time you had done or did maintenance on the generator? Burnished the slip rings, oil, oil filter, air filter? Do that if it's been a while.

Once that's done, then open the generator's control box with the generator off, and check all the wiring connections inside making sure they are tight. With situations where voltage is dropping too much, I always do a tug test of each wire connection...using around 4 lbs of pressure I try to pull the wire out of the connection. The wires should not pull out of course. I also clean up any corrosion and loosen and re-tighten any screwed down terminals.

Then follow the electrical output wiring to the RV wiring. Many times there will be a square electrical box in the generator compartment. Remove the cover and inspect any connections inside. Remove and replace after inspecting any wire nuts or wire connections.

I would of course have held onto the old thermostat unless it was defective...if you did that, put it back in place. I've run into smart thermos that weren't all that smart and did weird things.

After all that, then check out the AC. Note that when the line voltage sags, motors draw more current. The more current causes excess heating, which causes safety thermostats to pop open so things can cool down. So it's always best to try to keep the AC voltage as high as possible when it's running, especially when the sun is beating down on it. So switch it off for those short periods when running high current items, like the MW.

If that fan was damaged by the low voltage sag, it would behave like what you've described.

Come back and fill us in when you solve it...what you found, etc. Good hunting!

Originally Posted by Jkwilson1989

Number one rule of equipment maintenance is to go back to the last thing you fooled with. I’d swap the old thermostat back in to verify the new thermostat isn’t the problem.

Thank you both! I will start with another known good and compatible t-stat, as well as chasing and checking power from gen to AC. I have done reg oil changes on gen, but nothing else, will do that as well.

[gfourth]

The AC is a Coleman Mach 15 plus, here is the new t-stat I ordered to test:
https://www.rvproductsshop.com/9420a...ool-black.html

Can anyone confirm that this is a compatible t-stat? I'm pretty sure it is but it's also a little confusing trying to confirm that.

[RVfixit]

Just reading other comments, I don't think you have a thermostat issue. If the unit runs fine on shore power with the new thermostat, then you have other issues such as generator output. According to Coleman, your unit electrical draw on AC is 2050 watts at 115v (the rated voltage for this unit) equal to 17.8 amps max.

I would do a couple of simple checks first. Get yourself a simple outlet checker that will confirm that voltage polarity, output and common circuits are working correctly. Simply start the generator and plug it into an outlet. If normal, plug it into several outlets. It looks like this but there are many out there, this one is on Amazon for 6 bucks.


If readings are not normal, move on to next steps. Turn the genset off and connect to shore power, repeat test. If the outlets test normal now, you have a genset issue and will need to move to generator diagnosis. If still not normal, you most likely have a wiring issue related to the generator.

Next, if all checked out above, with generator running and all 120v appliances off, check voltage at any outlet. It should be at the rated voltage for the genset but in no case lower than 110v. Now run the ac, check the voltage. If it drops dramatically, it could be as simple as a voltage regulator at the genset.

Since your AC will not run on the generator I suspect an issue with wiring or the genset. Does everything else work normally on generator other than the AC?

[Jim_HiTek]

Originally Posted by gfourth

The AC is a Coleman Mach 15 plus, here is the new t-stat I ordered to test:
https://www.rvproductsshop.com/9420a...ool-black.html

Can anyone confirm that this is a compatible t-stat? I'm pretty sure it is but it's also a little confusing trying to confirm that.

RVP has a contact email. I'd feel safer if you contact them, give your heat pump's Model # and let them tell you.

One thing I learned the hard way is that these 'smart thermostats' for Coleman Mach machines aren't always that smart. The coders mis-read the AirXcel documentation on the one I bought and it was double pumping the power relays. Then the fist one the BT chip went bad, the 2nd free replacement the BT chip died too, and the 3rd one I just retired because each one of those smart thermos would double pump the main relays in the heat pump. And I'd write a complaint email. First one it was 15 seconds between Off/On cycles of the relays, than the 2nd one it was 4-5 seconds, until the 3rd model where it was just 0.5 seconds. I'm convinced that this double pumping ruined my older heat pump (burned out both compressor relays, than later the ODFM), then the 2nd killed my less than a year old replacement, I suspect. I detected the very short double pump in the 3rd replacement when I did a natural but unusual setting on the thermo and it did that very short double pump. That was it. Pulled off that thermo and it sits in it's box. Cost me $265 but I had to weigh that against the $4,000 I'd paid for a new heat pump. The original smart thermo was long past warranty when I associated the double pump of the power relays with the damage to the heat pumps.

Anyway, if you buy one, be careful to listen to what happens when the thermo calls for cooling/heat, and when it shuts it off. The ol' timey Coleman Mach True Air thermo never ever does a double pump. It was an Easy Touch Micro Air but could happen to any of them I suppose.

[RVfixit]

Originally Posted by Jim_HiTek

RVP has a contact email. I'd feel safer if you contact them, give your heat pump's Model # and let them tell you.

One thing I learned the hard way is that these 'smart thermostats' for Coleman Mach machines aren't always that smart. The coders mis-read the AirXcel documentation on the one I bought and it was double pumping the power relays. Then the fist one the BT chip went bad, the 2nd free replacement the BT chip died too, and the 3rd one I just retired because each one of those smart thermos would double pump the main relays in the heat pump. And I'd write a complaint email. First one it was 15 seconds between Off/On cycles of the relays, than the 2nd one it was 4-5 seconds, until the 3rd model where it was just 0.5 seconds. I'm convinced that this double pumping ruined my older heat pump (burned out both compressor relays, than later the ODFM), then the 2nd killed my less than a year old replacement, I suspect. I detected the very short double pump in the 3rd replacement when I did a natural but unusual setting on the thermo and it did that very short double pump. That was it. Pulled off that thermo and it sits in it's box. Cost me $265 but I had to weigh that against the $4,000 I'd paid for a new heat pump. The original smart thermo was long past warranty when I associated the double pump of the power relays with the damage to the heat pumps.

Anyway, if you buy one, be careful to listen to what happens when the thermo calls for cooling/heat, and when it shuts it off. The ol' timey Coleman Mach True Air thermo never ever does a double pump. It was an Easy Touch Micro Air but could happen to any of them I suppose.

Just curious, why did you feel you needed to move to a smart thermostat to begin with? I have one in my house but never felt a need to install one in my RV that I don't live in...

Safe Travels!

[Jim_HiTek]

Originally Posted by RVfixit

Just curious, why did you feel you needed to move to a smart thermostat to begin with? I have one in my house but never felt a need to install one in my RV that I don't live in...

Safe Travels!

I've been a full time RV'er for 21 years, and I live in my RV 365 for the most part. And as a retired electronics expert (21 years ago) I love new electronic gizmos. The TrueAir thermo is fine as far as it goes but having a Wifi and BT capable thermo is way cool. The company I bought from had been selling smart thermos for RVs for years and I kept waiting and checking for one designed for my heat pump for at least two years. When they came out with one, I jumped on it.

Things I wanted that were in the smart thermo: To be laying in bed, remembering I forgot to set the dumb thermo for 68 degrees, I'd have to get up to reset it. (I take my phone in the bedroom with me every night). But with the smart thermo, I could do that w/o getting up using the phones BT. And yes, I forgot all the time with the dumb thermo. Having the thermo Wifi capable meant I could connect it to my RV network, and while many miles away get online and set the temp for sudden weather conditions. Auto Range settings: I could set a smart thermo to days of the week and times of day to raise or lower the temp according to my lifestyle. Can also set them to cool most of the day, and heat at night. Especially handy up in the mountains.

So that's basically why I wanted one. It didn't work out this time, but I'm watching other brands currently.

[RVfixit]

I can understand that. My Home ac system is LG which has the ThinQ wireless system. I can control the HVAC, washer, dryer and any other appliances that are Bluetooth from LG. I do have two AC’s, a furnace and electric heat in my RV, never thought about adding a Smart Control system to it.

[gfourth]

Originally Posted by RVfixit

Just reading other comments, I don't think you have a thermostat issue. If the unit runs fine on shore power with the new thermostat, then you have other issues such as generator output. According to Coleman, your unit electrical draw on AC is 2050 watts at 115v (the rated voltage for this unit) equal to 17.8 amps max.

I would do a couple of simple checks first. Get yourself a simple outlet checker that will confirm that voltage polarity, output and common circuits are working correctly. Simply start the generator and plug it into an outlet. If normal, plug it into several outlets. It looks like this but there are many out there, this one is on Amazon for 6 bucks.
Attachment 441754

If readings are not normal, move on to next steps. Turn the genset off and connect to shore power, repeat test. If the outlets test normal now, you have a genset issue and will need to move to generator diagnosis. If still not normal, you most likely have a wiring issue related to the generator.

Next, if all checked out above, with generator running and all 120v appliances off, check voltage at any outlet. It should be at the rated voltage for the genset but in no case lower than 110v. Now run the ac, check the voltage. If it drops dramatically, it could be as simple as a voltage regulator at the genset.

Since your AC will not run on the generator I suspect an issue with wiring or the genset. Does everything else work normally on generator other than the AC?

Thank you, I do have one of those and will run that test. I did test the voltage and freq in different conditions and it checks out. Numbers in my first post.

[RVfixit]

Ok, I just reread your first post and missed that your tests showed 58hz under load. That means that the generator is running to slow under load and at that hz, electrical loads such as an ac can overheat causing a shut down. I suspect you have a generator issue, probably the controller or Voltage regulator, but diagnosis needs to be done first.

Let me know, Thanks

[gfourth]

Got the new t-stat installed, no change. AC/fan runs for 10 to 20 minutes, and then fan shuts off while compressor stays running. I was in there when it happened this last time and the sound/load on the generator does not change, meaning the AC is still drawing roughly the same amount of power. I'm going to pull the cover on the roof tomorrow and check all the wiring and connections

Originally Posted by RVfixit

Just reading other comments, I don't think you have a thermostat issue. If the unit runs fine on shore power with the new thermostat, then you have other issues such as generator output. According to Coleman, your unit electrical draw on AC is 2050 watts at 115v (the rated voltage for this unit) equal to 17.8 amps max.

I would do a couple of simple checks first. Get yourself a simple outlet checker that will confirm that voltage polarity, output and common circuits are working correctly. Simply start the generator and plug it into an outlet. If normal, plug it into several outlets. It looks like this but there are many out there, this one is on Amazon for 6 bucks.
Attachment 441754

If readings are not normal, move on to next steps. Turn the genset off and connect to shore power, repeat test. If the outlets test normal now, you have a genset issue and will need to move to generator diagnosis. If still not normal, you most likely have a wiring issue related to the generator.

Next, if all checked out above, with generator running and all 120v appliances off, check voltage at any outlet. It should be at the rated voltage for the genset but in no case lower than 110v. Now run the ac, check the voltage. If it drops dramatically, it could be as simple as a voltage regulator at the genset.

Since your AC will not run on the generator I suspect an issue with wiring or the genset. Does everything else work normally on generator other than the AC?

Tested with outlet tester on shore and gen, all good.

Originally Posted by RVfixit

Ok, I just reread your first post and missed that your tests showed 58hz under load. That means that the generator is running to slow under load and at that hz, electrical loads such as an ac can overheat causing a shut down. I suspect you have a generator issue, probably the controller or Voltage regulator, but diagnosis needs to be done first.

Let me know, Thanks

I will be doing as gen maintenance tomorrow as well. Oil is already fresh, I'll change the spark plug and clean the slip rings and check the brushes etc..

[gfourth]

I'm sitting on the roof while system runs to see what happens when fan shuts off. This RV is a 2013, and i bought it a few years ago with 6000 miles on it. It sat a lot near the coast.... the fan is very crusty but spins perfectly smooth. As it's running the fan motor is getting almost too hot to touch. Is that normal?

I've gone ahead and ordered another fan motor to swap it out.