120v Compressor only runs off Generator power - Printable Version

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+--- Thread: 120v Compressor only runs off Generator power (/showthread.php?tid=4997)

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120v Compressor only runs off Generator power - mycbarnes - 06-06-2019

Without a schematic drawing and this being against common sense I'll ask the group first. My 120v air compressor will only run if the generator is running. With shore power connected and L1 and L2 power showing voltage on the panel this makes no sense. Shore power and no generator the compressor won't turn on. Know the demand is there, the air system would be below cut in pressure for sure by a bunch. The AC bus I wouldn't think would parse out the 120v generator power exclusive to the generator and or the auto ac power transfer switching for the bus do anything but all or none generator or shore power. Maybe a relay somewhere to switch compressor from gen bus to shore bus  but I don't see a reason why.
Terry

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RE: 120v Compressor only runs off Generator power - bikestuff - 06-06-2019

Our coaches may be wired differently....

The first place to look is the sub breaker panel that feeds the 120V compressor. Do you have power at the compressor breaker? With shore vs generator vs inverter? You can use one of those nice little voltage detector things...but may have to take cover off the sub breaker panel to get to wires. Obviously don’t do this if you don’t feel comfortable with electricity.

On my coach the path of the power would be shore power->transfer switch->main breaker panel ->inverter->sub breaker panel->120V compressor.

The place that the generator and the shore power come together is the transfer switch. I would guess the problem would be there.

Bill

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RE: 120v Compressor only runs off Generator power - mycbarnes - 06-06-2019

Thanks Bill, I will start taking a volt meter to it tonight. I am an aircraft mechanic by trade, electronics school and Ham radio guy. I am comfortable troubleshooting most anything, thought I’d ask for clues from other owners as a start. Many thanks!
Terry

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RE: 120v Compressor only runs off Generator power - bikestuff - 06-06-2019

Great Terry! As far as I know the 120V compressor does not have any weird relay that would keep it from working. The “donuts” that feed the ammeters over the driver are in the main breaker box....and I think the wiring for the little L-1, L-2 lights are in the transfer switch.

I just recently realized that the 120V for the sub-breaker box is fed thru the inverter. It has its own transfer switch and is this is how the sub-breaker box can be fed from batteries / shore & generator power.

All this may be obvious to you...but in case someone else is troubleshooting I thought I would leave some bread crumbs.

Good luck.

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RE: 120v Compressor only runs off Generator power - Latitude 28 - 06-06-2019

Terry,
I just a similar issue that the compressor would not run on shore power.  Was not able to confirm if it ran off the gen or not.  However, we just came off of a three day trip for which the generator ran most of the time.....we maintained the air pressure the entire time. 

I notice the 12v compressor running the next day after getting home.  Starting the trouble shooting, after checking L1 & L2, I went after the AC compressor relay box in the R1 compartment that connects to the AC compressor pressure switch in that same compartment.  I would like to say I found something definitive.  Apparently a stuck relay was the culprit as the compressor is now working....that box was the only thing I investigated.

Good luck!
Steve

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RE: 120v Compressor only runs off Generator power - encantotom - 06-06-2019

if it runs on genny, then all the control relays for the compressor are fine.

that means it is most likely in the transfer switch in the inverter charger....that said, all the things that are on the inverter should be acting the same way. are they?

tom

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RE: 120v Compressor only runs off Generator power - mycbarnes - 06-06-2019

I didn’t make it out to my hangar to troubleshoot the coach tonight but the thread is leading me to first place to look and that is the inverter out bus and shore power bus relationships. Then the relay area Steve mentioned. We just got the coach and I am going through it waking it up from storage. I haven’t tried all the 120v stuff yet on shore power or checked all the 120v outlets

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