| Roof A/C out at 104F (of course) [message #317864] |
Mon, 22 May 2017 19:04  |
Luvn737s
Messages: 1106
Registered: June 2007
Karma: 2
|
Senior Member |
|
|
Working on the coach in preparation for Yosemite trip and A/C was working fine then suddenly the generator RPMS soared (probably to 2500 from 1800) and unit quit cooling. I adjusted the idle back down, but compressor would not kick on. Is this a symptom of a worn out start capacitor or maybe something more?
Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ
|
|
|
|
| Re: Roof A/C out at 104F (of course) [message #317867 is a reply to message #317864] |
Mon, 22 May 2017 19:53  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
|
Senior Member |
|
|
Chicken or egg. Did the RPM surge take out the roof AC or did the roof AC fail the the loss of load have the generator overspeed? In any event sounds like the governor needs to be lubricated before proceeding
John Lebetski
Woodstock, IL
77 Eleganza II
|
|
|
|
| Re: Roof A/C out at 104F (of course) [message #317872 is a reply to message #317864] |
Mon, 22 May 2017 21:06 |
Luvn737s
Messages: 1106
Registered: June 2007
Karma: 2
|
Senior Member |
|
|
The genset never bogged down much when the A/C compressor engaged and had been running at a constant 1800 RPM putting out 116v. Then is revved up to probably 2500 RPM and stayed there until I lowered the idle.
Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| Re: Roof A/C out at 104F (of course) [message #317898 is a reply to message #317894] |
Tue, 23 May 2017 07:44 |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
|
Senior Member |
|
|
Luvn737s wrote on Tue, 23 May 2017 07:59Since the fan still runs, is it worth it to try a start capacitor or just jump to replacing the A/C?
Randy,
For the cost, it sure is worth the try. While that could be the problem, I kind of doubt it. The good thing is that the sealed compressor motor is not likely to be hurt because is can't draw much current at the high frequency even with the expected higher voltage.
I don't know which manufacturer your unit is, but most that I have had open had a cut-out in the little box on the side that is held closed by a wire clip. That cutout is both temperature and current sensitive. Some also have a manual reset on that sensor (makes sense in a roof top unit with ~87 screws to access). There is not a high likelihood that the pump (compressor) is damaged, but the surrounding devices sure could be.
Wishing you luck
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
|
|
|
|
| Re: Roof A/C out at 104F (of course) [message #317899 is a reply to message #317864] |
Tue, 23 May 2017 07:51 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
It's called a 'volts per hertz' system, a design used in pretty much all the non-inverter small gensets. Spin it at the correct speed (1800 for a four pole alternator, 3600 for a two) and you get 60Hz. Consequently, engine speed government is essential. Overspeed will result in overvoltage, which will toast equipment if it's much over, and over frequency which will help toas electric motors. Baaad juju all around.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
|
|
|
|
|
| Re: Roof A/C out at 104F (of course) [message #317907 is a reply to message #317864] |
Tue, 23 May 2017 10:38 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
|
Senior Member |
|
|
The "maintenance" is as simple as drop of oil on each of the linkage parts. Duane Simmons would pull the oil cap dipstick assembly and use that as an oil drop applicator. Saved standing up and going to get the oiler when you were already seated on your work stool at the Onan. Pop the rod end and oil and replace per his video.
John Lebetski
Woodstock, IL
77 Eleganza II
|
|
|
|
|
|
| Re: Roof A/C out at 104F (of course) [message #317924 is a reply to message #317864] |
Tue, 23 May 2017 14:48 |
Luvn737s
Messages: 1106
Registered: June 2007
Karma: 2
|
Senior Member |
|
|
Went out the next morning and it started right up. I replaced start capacitor anyhow A/C ran for about 45 minutes and put out 60 degree air at 98 OAT. However, once I cycled it off it would not start back up. It's cooling now, so I'll see what happens.
Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ
|
|
|
|
|
|
|
|
|
|
|
|
| Re: [GMCnet] Roof A/C out at 104F (of course) [message #317943 is a reply to message #317899] |
Tue, 23 May 2017 20:08 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
|
Senior Member |
|
|
On May 23, 2017, at 8:51 AM, Johnny Bridges via Gmclist wrote:
> Overspeed will result in overvoltage, which will toast equipment if it's much over, and over frequency which will help toas electric motors.
Overspeed results in an over-frequency condition that is linearly proportional to the amount of overspeed but the excitation system has a limiting device - the thyristor - which puts an upper bound on excitation and thus an upper bound on output voltage. It is this device which prevents output voltage from soaring in a no-load situation but it also serves to limit maximum output voltage in any operational circumstance.
Many motors will tolerate an over-frequency condition but may draw increased current or deliver decreased speed due to flux saturation of their magnetic components. I have regularly operated 60Hz rated motors at 80Hz in CNC positioning applications but each motor design has differing magnetic characteristics so this statement cannot be extrapolated to the A/C compressor and fan.
Did the OP ever report back as to whether the A/C restarted after the short-cycle lockout timer expired?
—Jim
1977 Eleganza
1977 Royale
Hamilton, OH
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
