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bruceisla · 10-17-2013, 01:32 PM

Quote:

Originally Posted by adonh

I spoke with my RV shop that installed the AC and the tech wanted me to look for a sensor wire with a metal tip that should be inserted between the coils. I found it
Attachment 47946

He told this should regulate the coil temp and prevent freezing on the coils.It appears to be in place but I have not checked the other end to see where or if it is attached. I send them the picture and I am waiting on a call back.

Another question, the unit is off and with the ceiling cover removed I can feel cool air coming from the exhaust cool air side with the blower. It is cool outside today so this is outside air. Is that normal

No ... the A/C is a closed system and should not be open to the outside. Are you sure the cool air isn't coming from the ductwork ... that is, backwards from the other A/C or a draft from an open window recirculating thru the ductwork. You could check by duct taping (or masking tape) apice of paper over the return side of the housing (filter side) and also ver the duct openings ... if you still feel cool air it's coming from the roof side and you have an air leak in the plenum above the evaporator or possibly a leak in the seal from the Roof A/C to the roof itself (unlikely you would feel cool air ... usually just rain gets in).

That wire is your freeze detector ... it shuts the compressor off if it detects a freeze .... normally, if it is detecting freezes, you will get "short cycle" .... A/C compressor cycles on and off approximately every 2 - 3 minutes. The other end of the wire should plug into the control unit (the box directly above the filter and about 6 inches square by 2 inches tall).

However, it is a detector and not a preventer. The freeze (frost or ice) is already there when it shuts the compressor off. It restarts the compessor when the evaporator reaches about 42 degrees (if memory serves me)..

adonh · 10-17-2013, 02:09 PM

Quote:

Originally Posted by bruceisla

No ... the A/C is a closed system and should not be open to the outside. Are you sure the cool air isn't coming from the ductwork ... that is, backwards from the other A/C or a draft from an open window recirculating thru the ductwork. You could check by duct taping (or masking tape) apice of paper over the return side of the housing (filter side) and also ver the duct openings ... if you still feel cool air it's coming from the roof side and you have an air leak in the plenum above the evaporator or possibly a leak in the seal from the Roof A/C to the roof itself (unlikely you would feel cool air ... usually just rain gets in).

That wire is your freeze detector ... it shuts the compressor off if it detects a freeze .... normally, if it is detecting freezes, you will get "short cycle" .... A/C compressor cycles on and off approximately every 2 - 3 minutes. The other end of the wire should plug into the control unit (the box directly above the filter and about 6 inches square by 2 inches tall).

However, it is a detector and not a preventer. The freeze (frost or ice) is already there when it shuts the compressor off. It restarts the compessor when the evaporator reaches about 42 degrees (if memory serves me)..

I think you are right I am feeling the cool air from the duct. There is no air coming in from outside. They wanted me to move the freeze dedector down one row of coils so I will see what that does. Its starting to warm up here so I will turn it back on and check it out. Thanks for helping me on this.

bruceisla · 10-17-2013, 04:12 PM

Quote:

Originally Posted by adonh

I think you are right I am feeling the cool air from the duct. There is no air coming in from outside. They wanted me to move the freeze dedector down one row of coils so I will see what that does. Its starting to warm up here so I will turn it back on and check it out. Thanks for helping me on this.

You are welcome! keep in mind, the freeze detector is designed to prevent damage in the event the evaporator freezes. That's not what should happen!! it's a failsafe device. Actually, I think you probably fixed the problem by re-tapeing.

adonh · 10-31-2013, 10:31 AM

Quote:

Originally Posted by bruceisla

You are welcome! keep in mind, the freeze detector is designed to prevent damage in the event the evaporator freezes. That's not what should happen!! it's a failsafe device. Actually, I think you probably fixed the problem by re-tapeing.

Well it worked fine for more than a week and then it happened again. late afternoon unit on low fan set at 74 degrees. I caught it just as soon as water started to drip and turned it off for a while and then ran the fan only for about 15 minutes. Turned back to cool, low fan 74 degrees and worked fine until we headed home a couple;e of days later. I have been told it is probably caused by the high humidity and the low fan speed. But the temp outside was not that warm about 79 degrees and the compressor was cycling on and off. The front unit has not iced up at anytime. It s anew unit and hard to diagnose since since you don't know when it will happen.

TXiceman · 10-31-2013, 11:39 AM

Low speed is not a good setting to run the A/C. You get the same results as restricted air flow. Keep the fan on high speed.

Ken

adonh · 10-31-2013, 11:53 AM

Quote:

Originally Posted by TXiceman

Low speed is not a good setting to run the A/C. You get the same results as restricted air flow. Keep the fan on high speed.

Ken

I have not had icing problems during the hot summer months, 90 degrees + out side running on low fan speed with temp set at 74 degrees, even with high humidity. Compressor would not cycle on/off as often. Could the lower outside temp that we had under 80 degrees with the compressor cycling off for longer periods have played a role in the icing. This is the back unit and with only one window and the is shade usually down so the set 74 degree temp stayed cool for longer periods. I like the low speed fan because it is quieter, but will run high speed if necessary.

Thanks