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Old 07-20-2021, 11:05 AM   #1
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Dometic DuoTherm not blowing cold

I have a Dometic Duo-Therm 630035.321 in my bedroom not blowing cold. Fan works fine, compressor turns on and thermostat is in order. Front AC unit blows cold.

What I've done.

1. Turned the breakers off and on
2. Replaced the fuse
3. Cleaned the condenser coils
4. Cleaned the Air filter
5. Replaced both capacitors
6. Replaced the control box

One thing I noted when its running is the refrigerant lines are not getting cold. Assume these units are closed systems and can't try to add R-22.

Anything I am missing before I bite the bullet and replace the units on the roof?
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Old 07-20-2021, 12:14 PM   #2
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These are sealed unit and will require the addition of two ports to charge refrigerant. Are you sure it is R-22 and not R-134a or R-410a?

Have you checked the temperature across the unit when operating on high blower speed.

You need to use a thermometer and not an infrared or "laser" indicator. Read the temperature at the inlet to the unit and the closest to the unit. The outlet temperature should be 18 to 20degF lower than the inlet. If you are close to this temperature range, it is doing all it can do.

When was the last time you cleaned the filters and the evaporator coil or the condenser coil...you say you did?

The line from the evaporator to the compressor should be cool and probably sweating. The line from the compressor to the condenser should be hot.

What is the amperage the unit is pulling compared to the rated amperage? How old is the unit?

There is a lot of trouble of shooting to help you out. 90% of the time, the issue is NOT low refrigerant, but low or restricted air flow or the heat load is more than the unit can do.

Ken
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Old 07-20-2021, 01:25 PM   #3
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Check the change over valve (switch between AC and Heatpump). I not sure which way it is engaged for heat or AC. Each manufacture has it diffrent. In one of the modes if should click.

If the unit is setup as normaly a heatpump and and the change over valve does not entergize no ac
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Old 07-29-2021, 02:14 PM   #4
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Ken,

Have you added ports before as I think my issue is a loss of freon?

I've think I've exhausted everything i can think of short of replacing the unit. The unit is clean on top and bottom. Capacitors and control board have been replaced. I've reset the thermostat and get the FF code. I've also replaced the fuse just in case. Thermometer reads warm unfortunately with the unit on and compressor running. The line from the evaporator to the compressor is not cool or sweating and the other line is not hot while the compressor is running. The units are original in my 2005 Diplomat.

The front unit works great and blows cold. If I have to replace it, hoping I can replace just one unit. I've read that you can take the board off the old A/C and make a couple wiring changes that Dometic has documented. Trying to get them to answer the phone and talk knowledgeable is difficult.

I am home based in the San Francisco Bay Area.

Unless you can think of something else, I just need to get someone at Dometic to provide the steps to retrofit a single replacement and not replace both units. Hate to waste money replacing something that works just fine
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Old 07-29-2021, 02:47 PM   #5
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Good advice except IR laser thermometers are fine as long as you know how to use them. When I check the split temperature on my home AC I use a meat thermometer and stick it in a tiny hole the installer used at the inlet and exhaust of the evaporator. But I use an IR thermometer to check what's coming out of the overhead ducts to see how much I'm losing. Sure, you have to hunt around a bit to find the lowest temperature, but it works fine and beats pulling out a ladder.

I used my IR thermometer when PDIing my new Airstream trailer because I did not have a regular thermometer with me at the time.

Quote:
Originally Posted by TXiceman View Post
These are sealed unit and will require the addition of two ports to charge refrigerant. Are you sure it is R-22 and not R-134a or R-410a?

Have you checked the temperature across the unit when operating on high blower speed.

You need to use a thermometer and not an infrared or "laser" indicator. Read the temperature at the inlet to the unit and the closest to the unit. The outlet temperature should be 18 to 20degF lower than the inlet. If you are close to this temperature range, it is doing all it can do.

When was the last time you cleaned the filters and the evaporator coil or the condenser coil...you say you did?

The line from the evaporator to the compressor should be cool and probably sweating. The line from the compressor to the condenser should be hot.

What is the amperage the unit is pulling compared to the rated amperage? How old is the unit?

There is a lot of trouble of shooting to help you out. 90% of the time, the issue is NOT low refrigerant, but low or restricted air flow or the heat load is more than the unit can do.

Ken
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Old 08-06-2021, 07:08 AM   #6
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I just replaced my second unit.

If you have the 5 button control you have to buy a new board to make it backwards compatible. Go figure.

So I have two brand new boards now.

The modification is very straight forward and the documents are excellent.

What is a nightmare is getting an AC delivered that is not damaged in shipment.

Ordered the latest replacement. Surprisingly we received it much sooner than the last one and sooner than the predicted shipment date.

Now the disaster. The box looked typically beat up a bit but nothing out of the norm. Opening the box I found the thing had been dropped squarely on its nose. The AC frame looked like a crumpled front end from a car wreck. The shroud screw holes were broken. Inside the motor was torn from its mount.

So, back it went the next day. Bad news, to replace it the new price is $250 more. This is just in a few weeks of the last order.

A call to Amazon after working to find a human being they gave me a $200 credit and then the lady gave me another $50 the next week.

The bad AC was received by them and the CC refund was about 5 days out.

The new AC arrive really quickly, perhaps someone got a hot foot. I tried my best to open the box before the ups driver raced off but alas, only tail lights.

Yep, this one was dropped too but not from such a great distance. The frame was slightly bent and the shroud had but one hole cracked. Inspecting it closely there was not other damage. So I took a shot and installed the new board and got help getting it on the roof. To my relief it fired right up and is working fine. Except I had that cracked shroud screw hole.

They could not order me a replacement shroud. I would have to send the whole unit back again. I got creative and did get a replacement.

So my suggestion is to find a local dealer and pay the extra bucks so that you can open the box and take the shroud off before leaving the dealership.

None of my dealerships had them in stock of course so I opted for Amazon.

I definitely would not order it from some place that doesn't have such an easy replacement policy.

Sorry this is so long. Hopefully it will save you some grrr factor.

Oh yeah, the one I got after a two month delay last Summer had 5 physical defects inside. Wiring issues and simple mechanical issues but it was a disaster too. I contacted the company and they said Oh My. We will get back to you on this. NOT. However, the two new ones that came my way this last couple of weeks were put together properly. Just poorly boxed.
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Old 08-06-2021, 07:16 AM   #7
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IF you decide to replace both units, change the thermostat and you won't have to change the boards out.

There is a neat wi-fi thermostat out now but changing two ac's units and a thermostat at the same time could be a bit risky. The thermostat is a plug and play device.

One thing I found really curious was my front AC has 12 volt battery power run to it but the rear one does not.

The 12 volts must be routed to the thermostat??? So the rear one does not need the battery power. Or maybe I just missed something.

The schematics for the AC's are not good for sure.
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Old 08-06-2021, 07:19 AM   #8
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Quote:
Originally Posted by jondrew55 View Post
Good advice except IR laser thermometers are fine as long as you know how to use them. When I check the split temperature on my home AC I use a meat thermometer and stick it in a tiny hole the installer used at the inlet and exhaust of the evaporator. But I use an IR thermometer to check what's coming out of the overhead ducts to see how much I'm losing. Sure, you have to hunt around a bit to find the lowest temperature, but it works fine and beats pulling out a ladder.

I used my IR thermometer when PDIing my new Airstream trailer because I did not have a regular thermometer with me at the time.
I use an IR thermometer for everything. Iíve checked it against expensive digital thermometers we used when trucking. The IR is right on the money and instead of minutes it takes seconds. On hot days Iíll grab it on a quick stop and shoot temps of tires, check my fridge, electric plugs, transfer switch, inverter, and input and output of A/C

No RV owner should be without one, just like a good VOM with clamp on amp meter.
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Old 08-06-2021, 07:39 AM   #9
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I wouldn’t bother adding the saddle ports. If the Freon is gone, recharging the system is a temp fix at best.

I second Myron’s comments about getting an undamaged unit being difficult. In my case Camping World sent me a replacement and arranged for the damaged one to be picked up. No additional financial transaction was required. It’s a really simple repair if you get an in damaged unit the first time.-
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Old 08-09-2021, 12:49 PM   #10
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As said if they are heat pumps make sure the shuttle valve is working or it will not cool. The coil could be bad making it a simple fix. They valve itself would require opening the system which I would not pay to do. And yours should be the type that are heat on/ac off for the default position.
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Old 10-12-2021, 03:15 PM   #11
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I have the same DuoTherm A/C Heat Pumps in my motorhome with the identical problem. The problem was a bad Reversal Valve Solenoid which changes the default heat pump mode to A/C. I have had one orderd from McLains RV in OKC since late July and it hasn't come in yet and they don't know when it will arrive. I took the solenoid off of the rear A/C and put it on the front A/C and it worked as it should. In the meantime I found a reversal valve solenoid from a residential unit that works. The brand is a Ranco and the part number is LDK-310000-070. I installed that on the rear A/C and it works as designed. Hope that helps and gets your A/C working. Note: If the bakelite on the original solenoid is cracked, it will not work or it may not work long-(that info from another post somewhere on the 'net). Sorry for the late reply, but I just now seen this as I was scrolling through the Monaco Owners' Forum.
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Old 10-12-2021, 08:47 PM   #12
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Quote:
Originally Posted by MiKeMo View Post
I have the same DuoTherm A/C Heat Pumps in my motorhome with the identical problem. The problem was a bad Reversal Valve Solenoid which changes the default heat pump mode to A/C. I have had one orderd from McLains RV in OKC since late July and it hasn't come in yet and they don't know when it will arrive. I took the solenoid off of the rear A/C and put it on the front A/C and it worked as it should. In the meantime I found a reversal valve solenoid from a residential unit that works. The brand is a Ranco and the part number is LDK-310000-070. I installed that on the rear A/C and it works as designed. Hope that helps and gets your A/C working. Note: If the bakelite on the original solenoid is cracked, it will not work or it may not work long-(that info from another post somewhere on the 'net). Sorry for the late reply, but I just now seen this as I was scrolling through the Monaco Owners' Forum.
Thanks for the part # on the reversing valve. You just never know!
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Old 10-13-2021, 11:39 AM   #13
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I wasted a lot of money trying to fix one of our Dometic units. I had a repair shop add the saddle valves and recharge the unit, three times! Finally, I wised up and replaced it!
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Old 10-13-2021, 11:44 AM   #14
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Quote:
Originally Posted by MiKeMo View Post
I have the same DuoTherm A/C Heat Pumps in my motorhome with the identical problem. The problem was a bad Reversal Valve Solenoid which changes the default heat pump mode to A/C.

I have had one orderd from McLains RV in OKC since late July and it hasn't come in yet and they don't know when it will arrive. I took the solenoid off of the rear A/C and put it on the front A/C and it worked as it should. In the meantime I found a reversal valve solenoid from a residential unit that works.

The brand is a Ranco and the part number is LDK-310000-070. I installed that on the rear A/C and it works as designed. Hope that helps and gets your A/C working. Note: If the bakelite on the original solenoid is cracked, it will not work or it may not work long-(that info from another post somewhere on the 'net). Sorry for the late reply, but I just now seen this as I was scrolling through the Monaco Owners' Forum.
Good to know. I have the same unit (Duo_Therm 630516.321) and suspect i have a bad Revesing valve.

Not sure - I had a loud knocking/tapping noise coming from rear AC unit. I climbed up on the roof and pulled the cover. The noise was coming from the area of the reversing valve. I shut down the AC (and started reading the manual) to figure out what components are in that area. When I started the AC unit up the noise was gone. A couple of days later I heard it again.

So I figured I would order the Reversing valve and see if that fixes it. Problem is that is Out of Stock or on backorder everywhere. I did put in an order with NWRV Supply and they are expecting it in around November.

It's good to know there is an alternative supplier.
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