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Old 09-16-2017, 01:39 PM   #1
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Any A/C techs on here?

This is a follow-up to another post a while back. My front A/C is a Dometic Penguin II 13.5K heat pump that I bought new 2 1/2 years ago. Recently we were getting ready for a trip and I turned it on to 65 degrees the day before to cool the MH down to leave the next day. The next morning it was frozen up, compressor humming loudly, no fan running, water dripping on the floor beneath the unit! I opened the grill and there was a thin sheet of ice on top of the supply air duct. I turned the unit off, thinking that it would be OK after it thawed out. WRONG!

When I turned it back on, it did the same thing, except for the water. Compressor humming, fan not working. I removed the shroud and the fan was seized up. I was barely able to turn the cage by hand, but when I did it started running. Hoping everything was OK, I left it on, set to 70 degrees, while we made the short trip. When we got back the fan had stopped again and the compressor was extremely hot to touch.

I replaced the fan start capacitor and the fan works fine now, but it is not cooling. Air coming from the return air ducts is only about 8 degrees below outside air, and the compressor is still too hot to touch.

I tried switching the unit to heat and it works fine. That would seem to indicate that the reversing valve is working wouldn't it?

Is there anything else I can check or can I safely assume the compressor is toast?

Thanks for any help you can give!
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Old 09-16-2017, 01:44 PM   #2
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Compressor is toast......motor energized with lack of coolant flow thru compressor end due to icing condition from loss of fan
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Old 09-16-2017, 01:56 PM   #3
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That's what I was afraid of! I'm thinking I will replace it with a Penguin II 15K unit for better cooling.
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Old 09-16-2017, 02:08 PM   #4
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Quote:
Originally Posted by Old-Biscuit View Post
Compressor is toast......motor energized with lack of coolant flow thru compressor end due to icing condition from loss of fan
when coolant flow wasn't present or restricted, wouldn't there be a temp sensor to safeguard the compressor?
(don't mean i know it, but common sense leads me to think so ).
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Old 09-16-2017, 02:26 PM   #5
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when coolant flow wasn't present or restricted, wouldn't there be a temp sensor to safeguard the compressor?
(don't mean i know it, but common sense leads me to think so ).

Compressor motor humming and HOT.......
Motor SHOULD have shut down due to thermal overload. SHOULD HAVE!
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Old 09-16-2017, 02:55 PM   #6
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Heat Pump

If in fact the unit is a heat pump, when you switched to heat, and it produced heat, the compressor is not toast! It has to "compress" whether in cooling mode or heating mode. If you could barely rotate the squirrel cage, the problem is not the capacitor, rather the bearings in the fan motor itself. They are probably sleeve bushings rather than bearings, and as new as the unit is, probably were never lubed properly at the factory. The compressor has an internal overload that will open on over amperage or overheating. The internals in that can are cast iron, and will take a long time to cool down. Wait til tomorrow, power it up and make sure the fan turns. I'll bet it cools until the fan seizes again. A new fan motor is a whole bunch cheaper than a new unit!
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Old 09-16-2017, 03:16 PM   #7
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If the fan motor was siezed up then that would indicate that the bearings are bad.
You were able to "free" it up but it would just seize up again.
The issue of ice on the evaporator coil is because of no air flow through it which causes it to freeze up and subsequently leak water down through it as it thaws out.
With the condenser fan not working the refrigerant pressure goes sky high and normally the high pressure switch opens shutting down the compressor.
If it doesn't shut down it will overheat and the internal overload should save it.

Put in a new fan motor and hopefully you'll be ok.

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Old 09-16-2017, 03:58 PM   #8
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I read somewhere on here about a bad diagnosis on a roof air. Tech said it was bad needed replaced, and owner said it turned out to be switching valve in the unit. The unit while on cool was exhausting the cold air up out of the unit. If you can find it his results are easy to read. I hope this will help. Maybe first turn on cool and check the top of the unit for exhausting the cold air?
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Old 09-16-2017, 04:27 PM   #9
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If it is truly a heat pump..and it heats when set that way but doesn't cool, it could be the reversing valve that switches the coolant flow from cool to heat. That is what would happen if cool air is coming out the top of the unit.

Heat pumps are less reliable than regular units since they have a reversing valve in the refrigerant piping. I stopped using them a while ago for this reason. They aren't worth the price and reliability difference.

Newer RVs have electric fireplaces which eliminates the need for a heat pump. Both use electric and avoid the need to refill the propane tank during cold weather.
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Old 09-17-2017, 02:30 PM   #10
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Remember, the fan is working fine now that I have replaced the start capacitor.

Can the reversing valve be replaced?
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Old 09-17-2017, 02:48 PM   #11
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Generally reversing valves are hard to replace, even on a residential unit. It you are sure that the heat works, you might fiddle with the connections to the reversing valve and see if you can make it switch to cool.
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Old 09-17-2017, 04:12 PM   #12
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Remember, the fan is working fine now that I have replaced the start capacitor.

Can the reversing valve be replaced?
The fan is probably going to fail again. The start capacitor has nothing to do with the fan bushing/bearings being seized up. Those need to be lubricated if possible to keep the seizure from happening again.

I would imagine the reversing valve could be replaced but i'm not sure how practical or how often it is done on roof top units. I'm not an expert by any means but i figure some damage may have occurred when the compressor got so hot (more than one time). Myself, i would not want to throw too much money into it at this point.

This my opinion so hopefully you'll get a more reliable answer from an hvac technician that knows the business.
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Old 09-17-2017, 04:50 PM   #13
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You probably have 2 problems.

1) As others have mentioned, if the fan actually seized (you could not easily spin it by hand when the A/C was turned off), it will seize again.

2) As others have mentioned, if it works as a heatpump (outlet air temp is at least 20 degrees higher than inlet temp), the compressor is working. Likely to be a stuck reversing valve or bad reversing coil. Depending on your unit, it may default to heat or to cool. Sorry, I don't remember which years/models did what. At any rate, you are probably at the point where you would be throwing money at the unit.

Assuming you don't have a height issue (I don't have an issue on my Newmar), you may want to consider replacing your unit with a Dometic Brisk II which seems to have a better track record (they are about 4 inches taller). Note that a Brisk II doesn't have an integrated control board ... the controller is ordered separately ... the combined price (Brisk II + controller) is a few dollars less than a Penguin II with integrated controller. You will need to match a control unit to your 5 - button (call Dometic). Below is a 15K heatpump .... a 13.5K is about $150 less. Don't be tempted ... get a 15K.

Dometic White Brisk Air II 15K Air Conditioner with Heat Pump - Upper Unit - Air Conditioners - Air Conditioners - RV Appliances
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Old 09-20-2017, 03:39 PM   #14
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A little more information for your consideration. I was trying to decide if the problem could be the reversing valve or the control board.

Here's what I know now.

1. The reversing valve solenoid is activated in the heat mode. The heat pump works great in the heat mode.

2. The reversing valve solenoid is getting 120VAC when the system is in heat mode. I cannot tell if the valve is actually activating properly. It is obviously switching to the heat mode, but is it moving back for proper operation in the cool mode.

3. The reversing valve solenoid coil is supposed to read 465 ohms resistance (according to Dometic). It reads 740 ohms. That sounds like a big problem, but remember the unit is working fine in the heat mode, which is the only time this solenoid is activated.

4. When in cool mode the air coming out of the ceiling registers is about 12 degrees cooler than the outside temp.


Obviously, the control board is controlling the reversing valve solenoid as it should. The fan is running. The compressor is running. Is there anything else that could be wrong with the control board to cause this problem?

I've exhausted my very limited knowledge. Unless someone can tell me something else to check I guess I will have to buy a new heat pump!
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