While camping this past weekend (outside temp 75 and rising to 78 max) I set my rear Duotherm roof air conditioner for 74 degrees, Fan-LOW, left 2 windows ajar with two spoiled panting dogs and left for 4 hours. Upon my return I noticed the rear unit was no longer blowing air. I could feel a very slight amount of air being released (cold)..No warning lights-Green power light still lit. A noise that sounds like a motor emmitted from the unit- like the motor was struggling to turn? A pulsating low reverbarating kind of up and down hum? When I restarted the unit several times the same symptom would continue. I checked the incoming line voltage with my Fluke 77 and read 119 VAC. I left the unit OFF overnight. The following day I turned the unit back on and it is functioning normally again... ...any thoughts?

I had a similar issue with my Duo Therm - it ran erratically, then on my way to Carl Flack's, it quit (just after the engine A/C locked up again). While waiting for the engine to cool to check things out, I pulled the cover and the circuit board and found a couple of the wires from the ribbon cable broken.

I duct-taped them into contact so the A/C would run.

When I got to Carl's, thanks to his having a decent soldering iron, I desoldered the old joints, slit the ribbon cable between conductors about 1/2", stripped 'em, and resoldered.

Since then it's worked without fail.

Hey Thanks Rusty, I'll have a look and report back..Boy I'd have a tough time not spoiling those two retrievers of yours!

Rusty, the wires going into the circuit board are tight and solid. The other end with the plastic connector appears to be solid too. No cold solder joints found on the circuit board either. Any other things I can check for?

Not to rain on a parade, but I'd take that ohmeter, pull that board again and check each lead while wiggling the cable at the joint.

I had looked at mine before and concluded it was OK - but it turns out it wasn't. That's one of the problems with ribbon cables - the wires tend to hold the others in, and one can be misled about the integrity without subjecting the join to a little abuse.

If the front air is the same, you could swap the control boards and test run it hard and see what happens.

Just so you'll have it for reference, the operation is that when the A/C is switched on, the fan comes to High. After a 2-3 minute delay, the compressor kicks in; this operation is governed by the control board.

I just checked my prints, parts lists, and exploded diagrams, and I have nothing useful on the Duotherm...

Otherwise it sounds like a bad control board (its catalog name - the term "control panel" refers to wall-mounted/remote thingies.) or a bad start/run capacitor on the fan (but I'm not sure it's not a shaded pole motor on the fan). It surely sounds like a fan motor problem, and the issue of shutting down due to high heat (from running for a while) is symptomatic of a run capacitor gone defunct.

The compressor will shut down on overpressure/overtemp if the fan motor's not blowing over the condenser.

I'm sorry I don't have the electrical schematics to be of more help....

Simple solution seems to be that you froze your evaporator up by leaving the windows open.

Your unit was unable to cycle since it was trying to get the ambient temperature down while 'new' air was constantly being introduced at a temperature higher than its setting.In effect, your a/c was trying to cool off the entire outdoors. This caused it to ice up.

Air can't blow through a wall of ice, so you had minimal flow through the unit, but compressor was working so it was cool.

When you shut it off overnight, it thawed, hence the 'working properly' the next day.

No reason to leave the windows open for your dogs if the A/C is on. You have to choose one or the other.

If it is functioning normally, I would not mess with it.

Excellent possibility! Mine's iced up a couple of times (running on the road), but the fan motor never stopped.

Great information. I'll check continuity on the cable and test with the windows closed. I've never left the windows open in the past so Windsors explanation makes perfect sense too. My dogs gave me a dirty look when I went to close the windows so I had to compromise and leave them open halfway...next time they do that I'll bargain with them and leave the TV on..

Duotherm AC service manual available at:

http://users.sisna.com/cebula/acservice.pdf

3M size.

Mike

Very helpful! I downloaded it for my laptop, which goes wherever the Barth goes.

I thought I had a great idea with the new patio room. My roof air blasts plenty of cold air and I thought I'd just leave the door and windows open that are adjacent to the patio and cool it off out there a little too. The air is on anyway so I'm not wasting electricity by diverting some of the cool air to the patio, but Darryl,s post makes me think twice. Would a roof air freeze up like he's talking about? If so would it be damaged or just out of commission until it thaws? I often just close the screen door when at a park, and the coach stays nice and cool and I've never had a problem, but this has me wondering.

Danny, "It depends".

My own experience with roof air freezing is that it freezes more in high humidity and low fan speed. Also, setting it so cold that the compressor never gets to shut off will make freezing more likely, as the ice never gets to melt away.

So, I would say that if your AC is running on high fan speed, humidity is not too high, and the compressor gets to cycle, icing is less likely. Sometimes, when I had Dometics, medium fan speed was enough to prevent a recurrence of condenser icing.

A clean filter and condenser also helps.

Thanks bill, but you bring more questions to the board than answers. My Coleman Mach has Hi Cool, Lo Cool, Hi Fan, Lo Fan, and Off. So how does this effect my question of can I use the unit to somewhat cool the patioroom. I just read the first sentence of this post and it sounds like I'm dissin' bill. Nothing could be further from my intentions. bill is one of the folks I continually look to for accurate and useful info. I am, however, leaving it as posted in the hope of clarifying this matter.

IIRC, the Coleman uses an expansion valve and capilliary tube - these generally prevent iceup. (My Coleman died in the SOB two years ago, so I replaced it - the dealer had Carriers, and it's been fine). So I don't have the manual for it anymore.

quote:

Originally posted by Danny Zeeff:
Thanks bill, but you bring more questions to the board than answers.

Ow!

quote:

My Coleman Mach has Hi Cool, Lo Cool, Hi Fan, Lo Fan, and Off. So how does this effect my question of can I use the unit to somewhat cool the patioroom.

I was addressing the question of air conditioner icing icing. In an earlier post, you said, "Darryl,s post makes me think twice. Would a roof air freeze up like he's talking about?" I presume you meant the post by Windsor Dalrymple where he suggested that an AC could be frozen by leaving the windows open. I am presuming that his mention of leaving the windows open and your leaving the door open is similar.

I do not know your heat or humidity situation, but I mentioned it only trying to help, not confuse. Since you have two fan speeds I thought my mention of fan speeds would apply. Since you are trying to cool your patio, I thought my mention of allowing the compressor to cycle would apply.