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Old 10-07-2021, 01:35 AM   #1
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Brand: Thor Motor Coach
Model: Vegas 25.6
State: Louisiana
Posts: 27
THOR #14398
AC Chokes Out Generator

I have a 2018 Vegas 25.6 that has decided not to allow the roof AC to operate on the generator. It runs fine on shore power. I purchased the mh new in 2019, so it has been in service 2 1/2 years. I have a hard wired Progressive Industries EMS-HW30C. The generator has 40 hours on it. I have been negligent on "exercising" the generator, but have changed the oil.

I first noticed it in August when I tried to use the generator while traveling to run the AC. The generator would start w/o problem, but when the AC tried to engage the generator would choke down and stop. When the generator was choking down, a clattering noise was coming from the EMS. I left it alone, but tried it later on in the day and the AC came on and ran until we arrived at our campsite.

In September I was able to start it again while using generator. Last week I was attempting to exercise the generator by running the AC. The generator was again choked out by the AC startup. The EMS clattering noise was also back. I disconnected all power and opened up the EMS to check tightness of connections. All connections were tight. I left the EMS open and observed while the AC was engaging. The clattering was from the output wires connection of the EMS, both hot wires were arcing. See attached video - video not allowed.

I contacted Progressive Industries and was advised that there was no way for it to be arcing if the connections were tight. They suggested there must be a problem with the generator.

I disconnected the EMS and wired directly to power center. AC still choked down the generator, just no clattering noise. I wired EMS back into system and engaged AC again. This time I watched the digital readout on the AMS. Prior to AC engaging, display showed 117 v, 4 A, 61 Hertz, no errors. After AC engaged, display showed 61 Hertz, OFF, 14 A, OFF and blank due to generator being off.

I started generator and turned on electric heater, hair dryer, microwave, AC fan and all lights. Digital display showed 32 amps all powered by the generator without any issues.

A search of this forum and other sites on the web indicated that issue could be varnishing of carb and fuel lines due to not exercising the generator on a monthly basis, incorrect setting or stuck governor and possibly worn contacts on ATS. The governor seems to be working as the generator progressively increased rpms when increasing power usage in above paragraph.

I ran the generator for 3 1/2 hrs on a fuel mixture of 2 gallons of fuel and 8 oz of Sea Foam Motor Treatment. I know that this doesn't make up for not exercising on a regular basis, but had to try it.

I contacted Thor Customer Service to ascertain where I could find the ATS. I hope to check it tomorrow.

I have considered a Soft Start for the AC, but not ready to spend the $250 on a hunch. Plus the AC does not have any issues on shore power.

Has anyone else had this problem, how did you correct it?

Does anyone else have any ideas on what could cause this?

Thanks for taking the time to read.

Mike

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Old 10-07-2021, 01:55 AM   #2
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State: Florida
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THOR #7035
It sounds like you have a hard starting A/C.

You had 32 amps running from the generator on a 30 amp RV - sounds like it can do the job.

What it can't do is has enough in reserve to get that A/C running which is abnormal. SP has a lot more in reserve to overcome the hard start. I'd check/replace the capacitors on the A/C and see if that resolves it. If not, a soft start or new A/C may be in your future.

BTW, the generator speed stays relatively constant (it actually goes down slightly, called frequency droop) as you increase electrical load. What you are hearing is the throttle opening and the generator working harder with louder exhaust as the load increases.
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Old 10-07-2021, 02:40 AM   #3
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Model: Vegas 25.6
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THOR #14398
Thank you for such a quick reply!
I’ll check the capacitors this weekend.

Thanks again!
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Old 10-07-2021, 03:38 AM   #4
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Model: Citation
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THOR #8139
What AC unit do you have? Dometic Coleman?

Our generator seemed to run OK, tried Seafoam, didn't help, replaced the carburetor also didn't help

There are other hard start kits available, I got 1 made by/for our 13500 Dometic for $30.00 in 2020. Like most things it's " Currently unavailable"
NO problems since

Hope you find one, and it fixes your problem.
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Old 10-07-2021, 03:14 PM   #5
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Brand: Thor Motor Coach
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THOR #14398
Thanks for your assistance!
I have a dometic AC.
I am confused wit the terms “hard start” and “soft start”. Are they the same?

Again, thanks for the reply.

Mike
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Old 10-07-2021, 11:18 PM   #6
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THOR #8139
HARD SOFT & EASY start are interchangeable

$30+ for a bigger capacitor and a relay or $300+ for the same thing in a nice box

Check here, they have some in stock
You'll need your model # to find the one you need.

https://www.rvautoparts.com/33107310...e_p_29256.html
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Old 10-08-2021, 12:23 AM   #7
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THOR #7035
Hard Start and Easy or Soft start are NOT interchangeable.

A hard start kit is basically a larger starting capacitor which increases the angular difference between the running and starting coils providing more torque to start a hard starting compressor. But this increased torque comes at the cost of increased starting current - so this is the last thing you want if your generator is already struggling to start the A/C. The Hard start kits are pretty cheap to buy; generally a 2 figure purchase.

A Soft Start kit also includes a new starting capacitor but also includes electronics to limit current flow while starting allowing it to ramp up slowly instead of an immediate inrush. This is what you need for starting a hard starting A/C on a marginal generator but this kit cost 3 figures, quite a bit more than the Hard Start kit.
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Old 10-08-2021, 01:49 PM   #8
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Brand: Thor Motor Coach
Model: Vegas 25.6
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THOR #14398
Thank you Ted for that information. I hope to check out the current capacitors this evening or tomorrow.



One correction I need to make from previous post is that my AC is a Coleman Mach, not a Dometic. I dont think this matters other than getting the correct replacement capacitor if the original ones are bad.


Thanks,
Mike
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Old 10-08-2021, 03:21 PM   #9
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THOR #11130
You didn't mention spark plug(s) in your maintenance. It's the cheapest and quickest fix and the most common problem.
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Old 10-08-2021, 08:25 PM   #10
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Brand: Thor Motor Coach
Model: Vegas 25.6
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THOR #14398
you are right, I didn't mention spark plugs because I NEVER THOUGHT OF THEM! thanks for the reminder!


Mike
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Old 10-10-2021, 06:37 PM   #11
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Brand: Thor Motor Coach
Model: Vegas 25.6
State: Louisiana
Posts: 27
THOR #14398
AC Chokes Out Generator - Fixed I Think

Thanks to all that commented on my AC/Generator problem!

I checked the run and start up capacitors on the Coleman Mach a/c with a volt/ohm meter. They checked out at the 60 ohm and 7.5 ohm rating posted on each.

To be sure I checked them correctly, I took them to a local A/C supply house and had them test them.They confirmed what I had found. They also advised that they had other RVer's come in with same issue that had purchased a SUPCO SPP-6 hard start kit that resolved their issues. They sold me one for $10 and it seems to have solved the problem. The AC is able to start while on generator.

I had contacted a local RV dealer and they advised they had a replacement capacitor for the Coleman Mach AC for $50, then called me back to say they had erred in the price quote and it was actually $100. I'm not sure if it was a hard start kit or just regular replacement capacitors. I plan on going by next week to determine what exactly it was.

Thanks again for all the comments.

Mike
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Old 10-13-2021, 07:54 PM   #12
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Brand: Thor Motor Coach
Model: Vegas 2018 24.1
State: Florida
Posts: 176
THOR #12484
Quote:
Originally Posted by bulletbob View Post
I have a 2018 Vegas 25.6 that has decided not to allow the roof AC to operate on the generator. It runs fine on shore power. I purchased the mh new in 2019, so it has been in service 2 1/2 years. I have a hard wired Progressive Industries EMS-HW30C. The generator has 40 hours on it. I have been negligent on "exercising" the generator, but have changed the oil.

I first noticed it in August when I tried to use the generator while traveling to run the AC. The generator would start w/o problem, but when the AC tried to engage the generator would choke down and stop. When the generator was choking down, a clattering noise was coming from the EMS. I left it alone, but tried it later on in the day and the AC came on and ran until we arrived at our campsite.

In September I was able to start it again while using generator. Last week I was attempting to exercise the generator by running the AC. The generator was again choked out by the AC startup. The EMS clattering noise was also back. I disconnected all power and opened up the EMS to check tightness of connections. All connections were tight. I left the EMS open and observed while the AC was engaging. The clattering was from the output wires connection of the EMS, both hot wires were arcing. See attached video - video not allowed.

I contacted Progressive Industries and was advised that there was no way for it to be arcing if the connections were tight. They suggested there must be a problem with the generator.

I disconnected the EMS and wired directly to power center. AC still choked down the generator, just no clattering noise. I wired EMS back into system and engaged AC again. This time I watched the digital readout on the AMS. Prior to AC engaging, display showed 117 v, 4 A, 61 Hertz, no errors. After AC engaged, display showed 61 Hertz, OFF, 14 A, OFF and blank due to generator being off.

I started generator and turned on electric heater, hair dryer, microwave, AC fan and all lights. Digital display showed 32 amps all powered by the generator without any issues.

A search of this forum and other sites on the web indicated that issue could be varnishing of carb and fuel lines due to not exercising the generator on a monthly basis, incorrect setting or stuck governor and possibly worn contacts on ATS. The governor seems to be working as the generator progressively increased rpms when increasing power usage in above paragraph.

I ran the generator for 3 1/2 hrs on a fuel mixture of 2 gallons of fuel and 8 oz of Sea Foam Motor Treatment. I know that this doesn't make up for not exercising on a regular basis, but had to try it.

I contacted Thor Customer Service to ascertain where I could find the ATS. I hope to check it tomorrow.

I have considered a Soft Start for the AC, but not ready to spend the $250 on a hunch. Plus the AC does not have any issues on shore power.

Has anyone else had this problem, how did you correct it?

Does anyone else have any ideas on what could cause this?

Thanks for taking the time to read.

Mike
Donít neglect checking connections to the generator itself. There should be a long thread about my fiasco. Intermittent operation condition only when A/C was cycling. I found the vibration of the generator was causing a loose nut to arc shutting down the generator when A/C was drawing initial load. There was not enough room to tighten the nut at the factory so they just apparently said the hell with it. A couple washers fixed it.
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