Issue: evaporator/suction line freezing up in A/C mode.

Actions: Replaced fan motor and evaporator coil (no air coming thru old one/beat up petty bad).

Relevant Information:

Refrigerant Type: R???

Ambient Outdoor Temperature: ___ Degrees Fahrenheit


  • High Side not above 180
  • Suction abt 55.

Indoor Temperature Readings:

  • Ambient Indoor Temperature ___ Degrees Fahrenheit
  • Temperature 12 inches after Evaporator ___ Degrees Fahrenheit


  1. Can the suction line freeze up w/in-efficient compressor?
  2. Is this a sign of leaking valves Compressor - will not pump dwn suction/high below 70psi to condenser?
  3. Could unit just be severely overcharged??
  • 1
    It is very hard to understand what you're saying, and what your actual question is. – feetwet Feb 25 '18 at 4:36
  • Your question is really difficult to follow exactly what kinds of things you are asking and you do not supply any information. So put it into bullet points or number lists. I will attempt a small edit - you can edit the question further to make things more clear and add the information, ambient temp, indoor temp, refrigerant type, evaporator temp..etc.. – Ken Feb 25 '18 at 9:50
  • Icing evaporator / suction line usually is caused by undercharging, I see this regularly if it is an older system that is still pressurized I will check for leaks and recharge watching the super heat and sub cooling values. If the system has lost its charge then I will pressure test with nitrogen if I can't find a leak I will pull a vacuum below 500um, if the system holds the vacuum I will weigh in the correct charge and double check for leaks. If you are charging your system in most locations you are required to be licensed and some of the questions you are asking make it sound that u are not – Ed Beal Feb 28 '18 at 15:17
  • Do you mean there is ice on the suction /gas line at the compressor ? – blacksmith37 Apr 15 at 18:55

Because I can't fit everything into a comment I will ask questions that might supply you with an answer.

What Refrigerant are you dealing with R22 , R410A ???

1: What is ambient temperature? 2: What is Indoor Temperature with in say 20 feet of your return air duct ? 3: What is the air temperature on the exit side of your evaporator ? This Should be about 20 degrees below Inlet Temperature measured in step 2. So if Indoor Temperature measure din step 2 is 75 degrees, the Temperature Measured 12 inches after the Evaporator should be 55 degrees.

So if your Indoor Fan is not moving enough air (your temperature drop will be greater > 20 degrees - or this could freeze up evaporator ) or is moving too much air (Your temperature drop will not be enough < 20 degrees).

Since you replaced your fan - CHECK the Wire Taps for the proper speed settings!

4: Your Suction PSI will vary some with Ambient Temperature ..a general rule of thumb 225 on the high side and near 70 on the low For R22!

If your low side is fine and your high side is low - your compressor valves are probably leaking.

You show both High side (<180 PSI) and suction side ( @55) both are too low (R22) This means With an Evaporator Freezing up - This is usually an indication that you need to ADD Refrigerant.


Yes your assumptions are correct and your answer is the same thing I thought. However, adding R-22 does not correct anything - suction rises to 70psi but head pressure does not rise in conjunction at all.

Just for kicks and grins, I disconnected the condenser fan motor and that got the head/suction pressure up and then dropped back down to 55/180. O/S temp 75-19F I/D fan motor 1075rpms and tapped for the high speed (cooling). Ducts are all blowing.

I did replace the metering piston, thinking it might be sticking. It was sticking/hard to get out of old coil. I did change I/S EVAP COIL and put new piston in, in-addition to chg I/D fan motor (Old coil was beat up pretty bad and was not allowing air thru). Before I found I/D fan issue no problems.

The way I saw it w/o seeing the duct work (next), the unit is either severely overcharged or the compressor's valves are an issue (providing no issues w/duct). I have never had this issue before, friends in the business are at a loss also.

Thanks for your input, I will be working on it. Tony

  • When you say new piston are saying you changed the TXV thermal expansion valve? Have you verified the valve is working? Pull the sensor for the valve off the line warm it and see if it opens if you did not flow nitrogen when changing the coils out the valve may need replacing as the orifice in the valve may be full of gunk. Also after changing the coil did you pump the system down to get rid of the non compressibles? With an r22 system I would want to check everything and have it right because it is getting so expensive now. – Ed Beal Jul 6 '18 at 10:24

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