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Old 10-07-2020, 05:22 PM   #1
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Onan 4k Generator shuts down when the A/C compressor Cycles on

I need help, if anyone has experienced this, I would greatly appreciate a reply.
I have a 2012 Jayco ZX24 Octane Toy hauler with an Onan 4k generator. My current issue is when on Generator power, I start the A/C, when the compressor starts, it will kill the generator.
What I have done so far. The generator is running on fresh, non-ethanol fuel, the spark plug and air filter have been replaced, oil level is correct. A Hard Start Capacitor has been installed on the Coleman Mach Series, 15,000btu (a starting booster).
The ATS (automatic transfer switch) engages on generator, 120v reading. The electrical panel has had all of the circuit breakers turned off, leaving only the a/c breaker active. No electrical draws present. The generator is run to warm up, engage the blower to apply some load to the generator, after 2 minutes, engage the compressor, ATS begins clicking and the generator shuts down.
I have also started the generator, put a full electrical load on the system, all lights on, refrigerator, exhaust fans, microwave, TV, fans, the generator runs flawlessly.
Tested the ATS, when on generator power, 120v registered, on Shore Power 120v. When turning on the Generator, the ATS is a 120v until engaging the A/C, then the power drops to 6v and shuts off.
If on shore power, the a/c system works as designed, cools the camper to ice cold. Everything works as designed.
The generator restarts every time with no delay on restart.
If anyone has any input, I would be greatly appreciate any input

Taylor
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Old 10-07-2020, 05:52 PM   #2
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What code does the geny give you? (Outside start switch will be flashing)
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Old 10-08-2020, 08:40 AM   #3
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13, under voltage from what I can find.
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Old 10-08-2020, 09:04 AM   #4
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13, under voltage from what I can find.
Could be a governor issue, not letting the geny speed up to cover the sudden increase in load.
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Old 10-08-2020, 09:21 AM   #5
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It seems to me the low voltage shutoff for the generator is doing what it's suppose to do, shut the generator off when a low voltage situation occurs. The hard start capacitor will sometimes help in these situations but not always. Both rhe generator and A/C unit may have reached the point where the generator just can't handle the starting load of the A/C. A possible fix is installing a Microair Easy Start which could dramatically reduce the starting load of the A/C unit. If nothing else solves the issue it's worth looking into (fixed my A/C won't start on generator issue).
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Old 10-08-2020, 09:27 AM   #6
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A Hard Start Capacitor has been installed on the Coleman Mach Series, 15,000btu (a starting booster).
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I A possible fix is installing a Microair Easy Start which could dramatically reduce the starting load of the A/C unit. If nothing else solves the issue it's worth looking into (fixed my A/C won't start on generator issue).
He already did that.
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Old 10-08-2020, 09:34 AM   #7
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He already did that.
Read again. He installed a hard start capacitor. He did not install a Microair Easy Start unit. Two completely different animals.
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Old 10-08-2020, 09:50 AM   #8
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Read again. He installed a hard start capacitor. He did not install a Microair Easy Start unit. Two completely different animals.
My bad.
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Old 10-08-2020, 12:49 PM   #9
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Check the wiring first before installing anything new or different.

Make sure all the connections are good and tight between the generator and the transfer switch. You can check the voltage at the generator, and check that connection, then follow that wire all the way back to the transfer switch (just to make sure it hasn't been pinched or anything). Open up the transfer switch and make sure there's no scorching or melted or loose wires. Check the contacts in the ATS closely to look for carbon build-up on the contacts.

Sometimes ATS just dies; they're not a high quality and durable piece of equipment in my experience.

I just went through what I thought was a generator problem. It was throwing a "no voltage present" code and would shut down. Turns out it was a bad connection inside the ATS that was not allowing voltage to pass beyond that point. Every now and then it would throw the main generator breaker, leaving the motor running, but it wasn't generating any power. Most times, it would just shut down and throw the code.

From the sounds of it and based on what you shared, with the ATS clicking a few times, only showing 6V on the output side at the moment the AC begins to draw, then the generator shutting down, sounds like you either have a loose connection inside the ATS, or the contacts on the inside of the ATS are corroded or defective in some way, or your ATS is simply kaput.

With light or no load, the 120V will pass and allow a reading, but under load across a loose connection (like corroded contacts or loose wires inside the ATS), the volts will drop across that questionable connection, the genny will see that voltage drop, and it will shut down or throw the breaker on the generator, to avoid a fire.

My technician verified it was indeed the transfer switch by wiring the generator directly up to the main panel (after testing for voltage at the generator input to the transfer switch and getting 120V), firing up the generator and testing the various 120V appliances. Everything including the AC units fired right up, so he knew right away it was the transfer switch.
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Old 10-08-2020, 02:27 PM   #10
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We own a 2019 Melbourne Presitge class c. At the end of June we noticed our Ac Coleman Mach airexcel 15000 wasn’t cooling our coach. Unit sounded like it was struggling loudly. When we got home I started up on board generator and started Ac. As soon as compressor kicked on the generator powered off. We bought it to an authorized airexcel repair shop and we ordered a new unit under warranty on July 2nd and are still waiting they blame delay on covid. AC is supposed to get here Monday Oct 12 curious to see what the problem was
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Old 10-08-2020, 02:49 PM   #11
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Have you tried running everything else but the A/C on the generator?
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Old 10-08-2020, 02:52 PM   #12
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nope, manually manipulated the governor. System still shut down.
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Old 10-08-2020, 02:57 PM   #13
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2edgesword, I have also started the generator, put a full electrical load on the system, all lights on, refrigerator, exhaust fans, microwave, TV, fans, the generator runs flawlessly.
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Old 10-08-2020, 03:04 PM   #14
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Was the Hard Start Capacitor installed and then the problem came? I am thinking either the Hard start capacitator got wired backwards or a faulty unit from the factory.
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Old 10-08-2020, 03:42 PM   #15
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2edgesword, I have also started the generator, put a full electrical load on the system, all lights on, refrigerator, exhaust fans, microwave, TV, fans, the generator runs flawlessly.
I'm assuming the hard start capacitor was installed to try and remedy this problem. If that's the case the issue probably has nothing to do with the capacitor installation. Given what you've said it does seem to come down to the load requirement for starting the A/C triggering a low voltage shutdown of the generator.
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Old 10-08-2020, 03:49 PM   #16
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Then why does the air conditioner run fine on shore power? also Generator runs everything else except the air conditioner, its either the Capacitor or a seizing unit and given that it runs fine on shore power ?
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Old 10-08-2020, 03:50 PM   #17
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I'm assuming the hard start capacitor was installed to try and remedy this problem. If that's the case the issue probably has nothing to do with the capacitor installation. Given what you've said it does seem to come down to the load requirement for starting the A/C triggering a low voltage shutdown of the generator.
+1

Have you checked the wiring to the AC? The breaker for the AC? The wiring in the main panel to the AC circuit?

It's the 6V at the transfer switch output when the AC load is applied that seems to me to be pointing to the ATS? Along with OP stating that the ATS clicks repeatedly at the time the load is applied? The voltage drop itself is not all that surprising, but it should be pretty instantaneous. (side thought: if there is no shore power present, the ATS could be trying to switch from the generator to shore power?)

Have you tried to measure the voltage at the generator when the AC load is applied?

You mentioned that the microwave runs fine; can you run the water heater on electric and the microwave at the same time and take a reading at the output of the transfer switch? Other than the AC, those are going to be the heaviest loads in the rig.
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Old 10-08-2020, 06:11 PM   #18
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Was the Hard Start Capacitor installed and then the problem came? I am thinking either the Hard start capacitator got wired backwards or a faulty unit from the factory.
All of this was happening before the hard start capacitor was install.
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Old 10-08-2020, 06:17 PM   #19
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+1

Have you checked the wiring to the AC? The breaker for the AC? The wiring in the main panel to the AC circuit?

It's the 6V at the transfer switch output when the AC load is applied that seems to me to be pointing to the ATS? Along with OP stating that the ATS clicks repeatedly at the time the load is applied? The voltage drop itself is not all that surprising, but it should be pretty instantaneous. (side thought: if there is no shore power present, the ATS could be trying to switch from the generator to shore power?)

Have you tried to measure the voltage at the generator when the AC load is applied?

You mentioned that the microwave runs fine; can you run the water heater on electric and the microwave at the same time and take a reading at the output of the transfer switch? Other than the AC, those are going to be the heaviest loads in the rig.
Everything else runs fine on the generator. Including adding a blow dryer to the load.
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Old 10-08-2020, 07:41 PM   #20
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Time for a clamp-on amp meter.
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