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Topic: Cold & Hot Roof AC (Read 758 times) previous topic - next topic

Cold & Hot Roof AC

On the last day of my trip home in our new to us coach my rear AC started to blow cold and hot air.  About every 3 minutes it cycles between cold and heat.

 I tried re-setting the Duo Therm control system (turned system off, pressed mode and zone buttons simultaneously and then turned system back on) but it is still cycling between cold and heat.

Don't know what else to do, would like to avoid taking it in for service. 

Gary Mauck
Deerfield Beach, Fl.
2005 U320 40' PBGB

"Elks Care, Elks Share!"

Re: Cold & Hot Roof AC

Reply #1 –
Try this number.  Ask to talk to a tech support person.

Keith

Dometic Customer Support Center

2320 Industrial Parkway
Elkhart, IN 46516

Phone: 1-800-544-4881
CustomerSupportCenter@DometicUSA.com
Keith, Joyce & Smokey the Australian Cattle Dog
1995 U320 SE Extreme 40' WTBI Build # 4780, with a Honda CR-V hopefully still following behind.
Motorcade # 17030
FMCA # F422159

Re: Cold & Hot Roof AC

Reply #2 –
Quote from: GFM –
On the last day of my trip home in our new to us coach my rear AC started to blow cold and hot air.  About every 3 minutes it cycles between cold and heat.

 I tried re-setting the Duo Therm control system (turned system off, pressed mode and zone buttons simultaneously and then turned system back on) but it is still cycling between cold and heat.

Don't know what else to do, would like to avoid taking it in for service.

Are you sure that it isn't the compressor cycling in and out, possibly due to clogged up fins on the roof unit not allowing enough air to pass through it and freezing up?  That would be my first guess. 
Robert
Build # 5304
1998 34' U270 Cummins 6CTA8.3

Re: Cold & Hot Roof AC

Reply #3 –
When turning the A/C on after being off for hours it will blow cold air and within 3 or 4 mins the heat kicks in but the thermostat continues to indicate it is in cool mode.

  I have ruled out freezing up with the problem occurring within minutes of start up and because it goes to heat.
Gary Mauck
Deerfield Beach, Fl.
2005 U320 40' PBGB

"Elks Care, Elks Share!"

Re: Cold & Hot Roof AC

Reply #4 –
Are your units heat pumps or are they standard A/C units with heat strips?

Pamela & Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Cold & Hot Roof AC

Reply #5 –
Pamela & Mike the units have heat pumps
Gary Mauck
Deerfield Beach, Fl.
2005 U320 40' PBGB

"Elks Care, Elks Share!"

Re: Cold & Hot Roof AC

Reply #6 –
Almost sounds like a goofy reversing valve or circuit controlling it. Or, there is a defrost cycle going on.
1998 U270 34'

Re: Cold & Hot Roof AC

Reply #7 –
Without being there to see it first hand it seems like the swap over valve (revers flow valve) relay isn't staying energized. If you have a wiring diagram you should be able to find the relay that controls the valve that swaps to either on cool or heat. Apparently the relay is functioning  because you said that it swaps from cool to heat, it just won't stay there. If you are a tinkering kind of guy, after you kill the power to the unit pull the covers and look for loose connections or corrosion where the relay is hooked up. This would be the best & cheapest thing that you could find and fix. There are other things but this should give you a starting place.

Pamela & Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Cold & Hot Roof AC

Reply #8 –
My experience ::)

Had the same issue with SOB because system wasn't used all the time.

So I moved the selector switch (while off) from heat to cool back and forth, to use the contacts, probally 5 times in 4 hours, turned it on - worked like it was fixed, but after about 6hrs on it started again. So I did the switch again. After 2-3 days of repeating this, no more problems.

Cant tell how many memory cards, hard drives, viedo boards I have taken out and re-seated to fix hardware. Thank you, the service call is $$$, took 15 minutes.
If its is an electronic theromstat, try taking the stat off the base plate and reseating it.

Hope it is not one of the more expensive suggestions offered.
The selected media item is not currently available.
My advice and experiences are Free, you decide if they are worth anything .

John - driving Old Faithful
1994 U280 GV
C8.3, Banks, Pacbrake, 900 watts, Resonator, XLHD tow dolly
Retired Army Warrant Officer

Life is what you make of it - if it is lemons, make lemonade!
Former Coaches:
1988 GV 40' ORED 300HP CAT - 9 years
1990 Winnebago LeSharo - 3 years
2000 Newmar London Aire - 3 years (#18 of 23 produced)

Re: Cold & Hot Roof AC

Reply #9 –
Dometic customer support said most likely it is either the reversing valve or solenoid coil.  If it is the reversing valve I will have to replace the A/C, just what I did not want to hear.
I'm trying to figure out from the wiring diagram were the valve and coil is located, not having very much luck so far.

Out of curiosity I'm going to run unit on heat and see if it will cycle to cold, if it does not cycle to cold my thinking is that would eliminate the reversing valve causing the problem?

The therm is electronic, do not understand what the stat is on the base plate, maybe I'm in over my head but it won't be the first time.



Gary Mauck
Deerfield Beach, Fl.
2005 U320 40' PBGB

"Elks Care, Elks Share!"

Re: Cold & Hot Roof AC

Reply #10 –
If you pull the top cover off you will be looking for something that looks like this.

http://image.made-in-china.com/2f0j00tviaeSQWvHcU/4-Way-Reversing-Solenoid-Valve.jpg

 Now this is just an example I don't have a pic. of the exact one here with me.

Pamela & Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Cold & Hot Roof AC

Reply #11 –
Mike, looks like my experience has been over ridden by folks who have more experience.
The stat is thermostat.
The selected media item is not currently available.
My advice and experiences are Free, you decide if they are worth anything .

John - driving Old Faithful
1994 U280 GV
C8.3, Banks, Pacbrake, 900 watts, Resonator, XLHD tow dolly
Retired Army Warrant Officer

Life is what you make of it - if it is lemons, make lemonade!
Former Coaches:
1988 GV 40' ORED 300HP CAT - 9 years
1990 Winnebago LeSharo - 3 years
2000 Newmar London Aire - 3 years (#18 of 23 produced)

Re: Cold & Hot Roof AC

Reply #12 –
John, I meant to ask is resetting the stat accomplished by removing all the wires and reconnecting or just the hot?

Mike, thanks for the valve image, coil should be fairly easy to id. 

Very much appreciate you guys taking the time to advise and educate....and hopefully ill save coach bucks, don't know what that means but with the word coach I assume it means a lot of $$$

Gary Mauck
Deerfield Beach, Fl.
2005 U320 40' PBGB

"Elks Care, Elks Share!"

Re: Cold & Hot Roof AC

Reply #13 –

Gary,
1 coach buck = aprox $1000

P & M
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Cold & Hot Roof AC

Reply #14 –
With my boats they are called BOAT bucks as in Bring Out Another Thousand.  Airplanes tend to be the same.
Steve DeLange
2005 U320T 40'
Pearland, Texas

Re: Cold & Hot Roof AC

Reply #15 –
Well, if the unit actually makes hot AND cold (good hot, and cold)...then the reversing valve probably isn't sticking.

I've known people to have stuck reversing valves on their boat A/C units and they tapped on them and it worked. Also, the external coil can burn up, but is easily replaced.

Perhaps yours just got a little sticky.

Or, it is going into a defrost mode of some sort.

You need to determine if the actuation of the reversing valve is commanded by the control system, or if it is commanded and mechanically sticking/moving.
1998 U270 34'

Re: Cold & Hot Roof AC

Reply #16 –
Gary, give it a try. Like I said use is good.
The selected media item is not currently available.
My advice and experiences are Free, you decide if they are worth anything .

John - driving Old Faithful
1994 U280 GV
C8.3, Banks, Pacbrake, 900 watts, Resonator, XLHD tow dolly
Retired Army Warrant Officer

Life is what you make of it - if it is lemons, make lemonade!
Former Coaches:
1988 GV 40' ORED 300HP CAT - 9 years
1990 Winnebago LeSharo - 3 years
2000 Newmar London Aire - 3 years (#18 of 23 produced)

Re: Cold & Hot Roof AC

Reply #17 –
With the information from the forum members on trouble shooting the A/C I was able to identify the coil was the problem.

The coil was getting hot when the unit was blowing cold and when it cycled to heat the coil would cool down.  Once the coil cooled the unit would go back to cooling.

The marine supply house were I purchased the coil told me as long as the unit was cycling between hot and cold the reversing valve was functioning.  Valve is suspect when a unit does not cycle.

Gary Mauck
Deerfield Beach, Fl.
2005 U320 40' PBGB

"Elks Care, Elks Share!"
 

Re: Cold & Hot Roof AC

Reply #18 –
Glad to hear you got it working. Also, thanks for the update and feedback.
1998 U270 34'