Air conditioning conundrum

[PapaRed]

2004 Itasca Meridian 36G
Basement air Model No. 6535-671
Ser No. 080313859

History:
Aug 2018 R&R outdoor Fan Bearing. (Noisy operation)
Apr 2019 R&R outdoor fan start capacitor (fan would not run, A/C shuts down)
Jun 2020 During a recent trip, turned system on, compressors came on, but outdoor fan not running. At next campground where maintenance was not allowed, they offered me the business card of a mobile RV tech allowed to work on the property. I had to whine and plead for him to even look at it, him saying he was certified on rooftop units, but not this one. After several minutes of pleading, I showed him how to drop the unit and troubleshoot. Capacitor checked OK, squirrel cage free to turn. Started unit outside the coach and it operated normal!

Installed unit, outside fan did not operate. Manually turned the squirrel cage (underneath through the screen) and it started! Of course, yesterday as we approached Phoenix, AZ it would not run. Thinking I would need a new motor, I dropped the unit once again today to find a part number. Turned the unit on with the coach plugged in to 30 amp power, unit operates! Both compressors operating, drawing 30 amps. Shut down, started again with genset powering the coach. System operated normal, start up drawing initial 24 amps, again drawing 30 amps with both compressors running. Don’t want to reinstall the unit without doing anything, but don’t want to buy a motor unless it is needed. Your thoughts, please.

[BobC]

I'd suspect a loose or corroded connection or faulty wiring. If that's the case, dropping the unit could temporarily improve things. Note the same could be true of something internal to the motor (does it have replaceable brushes). You might want to try wiggling or otherwise moving all connections/wires, being careful of the shock danger and shorts by using a stick or some other insulated tool.

Here's a link to a service manual that may help track down the problem. It has some extensive troubleshooting info:

http://www.rvcomfort.com/pdf_documen...6323_copy8.pdf

Good luck and let us know what you find out.

[PapaRed]

Thank you BobC for the link.
Reviewing the manual again gave me some things to check. BTW, in troubleshooting after my initial post, I was able to get it running, shut down and after a delay it did NOT run. So I'm convinced it is a bad connection or a loose ground. I did not know the motor black wire has a fuse?! I will continue troubleshooting in the AM. Thanks again!

[PapaRed]

Update.
BobC's response caused me to read the book again, and I determined (thought with some trepidation) the outside fan motor was bad. After discovering the motor price was north of $300, I wanted to make sure. Not being an electronic guy, my check of the capacitor (with an analog meter) may not have been conclusive, I decided to spend $9 and change that first.

After installation, the unit started just as the book described, the start-up amperage reading 28 amps, and with both compressors and fans operating, the amperage settled at 26 amps. Shut down, and after a 15 minute delay, restarted normally. Will do this several times before wrestling that big box back into its' hole!

[Morich]

You mention a delay. Do keep in mind there is a delay needed to let the compressor go back to normal!! Some have the delay built in but we can forget small stuff like that.

Another small point to think about and check. There are often two caps, a start and a run cap and since they are both prone to aging, I am inclined to change both if one goes as they are reasonably cheap compared to the big buck items which they help protect. Not sure of your unit so look for a second, perhaps?
Anything you can do to lube the motor shaft, etc. is really good, too.

[BobC]

Originally Posted by PapaRed

Update.
BobC's response caused me to read the book again, and I determined (thought with some trepidation) the outside fan motor was bad. After discovering the motor price was north of $300, I wanted to make sure. Not being an electronic guy, my check of the capacitor (with an analog meter) may not have been conclusive, I decided to spend $9 and change that first.

After installation, the unit started just as the book described, the start-up amperage reading 28 amps, and with both compressors and fans operating, the amperage settled at 26 amps. Shut down, and after a 15 minute delay, restarted normally. Will do this several times before wrestling that big box back into its' hole!

I hope I'm as lucky, I have a problem with compressor #2 not kicking in consistently.

And thanks for your Air Force Service. My dad served for 24 years and I served a short stint in the early 70s.

Bob

[NeilV]

The compressors on the basement air units have a solid state hard start device on each of the capacitors which do heat up and fail at times and they will become flaky as they start to fail. When you get the OEM capacitor set for the basement air compressors new hard starts should be included since best practice is to always replace both the hard start and the capacitor regardless of which one has failed. The hard starts may start to discolor and become quite brittle as they fail so that they may fall apart in your hand so caution is advised. The solid state device is slid inside the plastic holder so that the pressure on the spade lugs from the plastic case is all that keeps them connected to the device inside so once it gets hot and the plastic deforms or turns color that connection has become compromised.

The best way I know of mitigating this so that it does not happen very often is the get an AutoFormer to prevent low voltage damage to the hard starts and capacitors. Its been a decade since I put one on my coach and I have not had a capacitor, hard start or any other 120 volt electrical component fail since.