Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

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Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

August 22, 2016, 11:44:04 am

Our 1997 U270 36' has the standard 2 roof mount a/c units with heater strips. I think they are Penguin units with a single Duotherm thermostat that controls both programmed to work both in Zone 1. I have run both and they worked fine and made cold air using the 8KW genset. A month later now and only the front unit blows cold...the unit in the bathroom ceiling blows but never cold and I don't hear the compressor start even after several minutes even with the thermostat set at 62F while it is 80F out.. So...what to do. Is there a way to force the compressor to start or perhaps there is a trick...could it mysteriously lost it's freon charge? I tried getting the unit to cool using both the genset and 30 amp shore power with the 120v circuit breaker to the front unit off...no cooling but the fan always works fine.

Luckily the front unit cools well and the U270 1997 has ducted air so for now one unit is enough. If I have to replace the rear roof unit I would really like to have it on a separate thermostat so I can easily just run one unit when on 30 amps. Can I mount a new unit myself (I am handy) just not sure how to hoist in onto the roof? Is it worth trying to fix the failed unit compressor start cycle? Best source and cost of a replacement unit?

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #1 – August 22, 2016, 02:13:33 pm

Carl,

Don't throw the Penguin in the dumpster yet! There may be hope...

I don't do air conditioner repair, so no direct knowledge. There are "capacitors" in the A/C unit that have to do with starting and running. These are often cited on the Forum as sources of trouble. Try reading through the 2 links below for more info:

Penguin AC help needed

http://beamalarm.com/foretravel-links/PDF/dometic_penguin_manual.pdf

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #2 – August 22, 2016, 02:48:07 pm

We've had Penguins on previous coaches, liked them. One failed the same as described. My tech of 30 years said, "it's the compressor, want us to have it re-built ? Prolly, in labor, and parts, it will be a slam-dunk to just replace the unit. Plus you get warranty, fresh gasket". It could be a strange wiring problem, but I doubt it. Do get a unit with a heat strip, we miss those on our Carriers.

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #3 – August 22, 2016, 02:54:00 pm

Carl,

We have a '97 320 and our Duotherm thermostat controls the rear A/C on Zone 2. I would think that a 270 would have 2 zones also. See if you can get zone 2 to come up (push the 2 top buttons at the same time & release) and see what the temp. is setting at before you start throwing parts at it. I doubt that the unit has died but it could be a relay or something small like that.

Pamela & Mike

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #4 – August 22, 2016, 02:58:07 pm

Sounds like zone 2 is set for fan only

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #5 – August 22, 2016, 03:23:46 pm

It could be that you have the infuriating 4 button thermostat issue and aren't able to bring up zone 2 on the display.... Is there an unlabeled little black device on the wall in the bedroom near the light switch? If so, that is the temperature sensor for zone 2 (rear air). You have to press the mode and fan buttons simultaneously in order to change zones. If one of the buttons doesn't register a press, no amount cursing or supplication will change the zone.
Don

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #6 – August 22, 2016, 04:05:41 pm

Thanks Everyone...Wondered what that strange black thing was in the bedroom...now I now. I think both a/c units are programmed (along with the LP furnace) to be controlled as zone 1...and they all worked there until recently when the rear a/c blows just air now. But it would be helpful to have the rear on zone 2 so I dont have to run both or use the a/c circuit breaker to shut one off when I only have 30 amps (like in my storage parking area). So I will try to "move" the rear a/c to zone 2 on the thermostat and then if that doesn't fix it I will test the capacitors...failing all that and if it just blows air with no compressor start will probably bin it and replace with new unit.

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #7 – August 22, 2016, 04:41:51 pm

Quote from: Carl Cox – August 22, 2016, 04:05:41 pm

Thanks Everyone...Wondered what that strange black thing was in the bedroom...now I now. I think both a/c units are programmed (along with the LP furnace) to be controlled as zone 1...and they all worked there until recently when the rear a/c blows just air now. But it would be helpful to have the rear on zone 2 so I dont have to run both or use the a/c circuit breaker to shut one off when I only have 30 amps (like in my storage parking area). So I will try to "move" the rear a/c to zone 2 on the thermostat and then if that doesn't fix it I will test the capacitors...failing all that and if it just blows air with no compressor start will probably bin it and replace with new unit.

I do not think you can control both airs on one zone. You must switch the control as stated to bring up zone two.

If it will not work the controller can be reset.

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #8 – August 22, 2016, 08:42:48 pm

Someone may have changed the dip switch settings and did not turn on the zone 2 switch for the rear ac These are located on the board up top in the ac, also there is a forum member that rebuilds the 4 button comfort controls which is the thermostat that you turn things on and off.

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #9 – August 22, 2016, 10:53:32 pm

Maybe this won't help you but for the benefit of other readers, if you have two identical units and one of them still runs you can swap parts back and forth until you figure out which part takes the problem with it. If there's a problem it's most likely to be the capacitor. This can be a $5 part depending on what type capacitor you have. It's also likely to be a relay that starts the compressor, which can also be a $5 part. Follow the usual safe work practice of turning off all sources of power to the unit(s) you're working on. Also discharge the capacitor by putting a screwdriver across the terminals before you touch it. If you isolate the compressor and test it with an ohm meter it should not be shorted out to the case, nor should it be an open circuit. If you find a data plate on the unit it may tell you what the FLA (full load amperage) of the compressor is and what the LRA (locked rotor amperage) of the compressor is. These figures are useful if you can get the compressor running, even for a moment, and use a clamp on meter to check the amperage. These readings will tell you if your compressor is still good. Any good HVAC mechanic should be able to help you troubleshoot this, especially if you drive your coach down to their shop. If your compressor is bad you should probably replace the whole unit. Honestly, I'd look for a matching pair of used R22 units in good condition rather than buying the new R410a system. Read some of the reports people have written about the new units and then consider that a matching pair of good used units will probably cost less than a single new unit that won't match your current unit. You can get by with one unit for a while until you locate a nice matching pair of used ones.

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #10 – August 22, 2016, 10:55:41 pm

We have the same year. Try the two button push as suggested. Then toggle through. Should you have button push issue, there are replacement control boards for the units and a five button replacement for thermostat.

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #11 – August 23, 2016, 09:51:38 am

Hi guys,

If you change a dip switch setting on a Dometic air conditioner board, you then need to do the reset procedure in order to copy the new setting into the thermostat.
Jim

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #12 – August 23, 2016, 07:54:29 pm

Jim is the one that fixes the 4 button boards

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #13 – August 24, 2016, 10:13:13 pm

Problem solved.....well...thanks to the comments here I was able to determine that indeed the aft a/c is already programmed for zone 2 and it must have been on "fan" so I thought it had a compressor start problem. But once I got the thermostat into zone 2 I was able and set for "cool" it acts fine and cools slightly cooler than the front unit (I think it may have be a replacement unit though the same Penguin model by the previous owner). Thanks to everyone here for the comments....you are the best tool in my box! Loving our new U270....truly a fine coach.

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #14 – August 25, 2016, 12:07:34 am

Quote from: Carl Cox – August 24, 2016, 10:13:13 pm

Problem solved.....well...thanks to the comments here I was able to determine that indeed the aft a/c is already programmed for zone 2 and it must have been on "fan" so I thought it had a compressor start problem. But once I got the thermostat into zone 2 I was able and set for "cool" it acts fine and cools slightly cooler than the front unit (I think it may have be a replacement unit though the same Penguin model by the previous owner). Thanks to everyone here for the comments....you are the best tool in my box! Loving our new U270....truly a fine coach.

We have all been there

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Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

August 22, 2016, 11:44:04 am

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #1 – August 22, 2016, 02:13:33 pm

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #2 – August 22, 2016, 02:48:07 pm

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #3 – August 22, 2016, 02:54:00 pm

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #4 – August 22, 2016, 02:58:07 pm

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #5 – August 22, 2016, 03:23:46 pm

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #6 – August 22, 2016, 04:05:41 pm

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #7 – August 22, 2016, 04:41:51 pm

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #8 – August 22, 2016, 08:42:48 pm

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #9 – August 22, 2016, 10:53:32 pm

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #10 – August 22, 2016, 10:55:41 pm

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #11 – August 23, 2016, 09:51:38 am

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #12 – August 23, 2016, 07:54:29 pm

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #13 – August 24, 2016, 10:13:13 pm

Re: Rear roof mount a/c unit compressor will not start..only blows air on 1997 U270.

Reply #14 – August 25, 2016, 12:07:34 am

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