Compressor cycling fix
Senior Member
Joined: Dec 2011
Posts: 13,811
Likes: 3,184
From: Texas
After all the new work on mine, nothing is better. When the temp rises above high 80's. for some weird reason I stop getting solid 40 degree vent temp and the compressor starts cycling at 42 up to 46 , then back down and on, aon, and on........never cooling in the cab well!
91 today and 90 percent humidity.
91 today and 90 percent humidity.
Member
Joined: Feb 2013
Posts: 26,680
Likes: 6,253
From: Big Easy
No, the intake air is drawn in for both the heater core and evap core thru a central place, the air is then blended via the blend door that separates the two different cores to, well.......blend the air together for what ever setting you select with the temp switch. Blend is exactly what it's doing hence the name.
With the switch by passed in such a way you will still wind up with a block of ice that will not allow air to flow at all thru the evap core.
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Member
Joined: Feb 2013
Posts: 26,680
Likes: 6,253
From: Big Easy
After all the new work on mine, nothing is better. When the temp rises above high 80's. for some weird reason I stop getting solid 40 degree vent temp and the compressor starts cycling at 42 up to 46 , then back down and on, aon, and on........never cooling in the cab well!
91 today and 90 percent humidity.
91 today and 90 percent humidity.
What all did you have done?
.
Senior Member
Joined: Dec 2011
Posts: 13,811
Likes: 3,184
From: Texas
My EXCELLENT NEW DEALER quickly and correctly diagnosed that one of my fans was dead and the other was working on high only when the AC was on. Instead of both on low speed when the AC was on, as it should be. They replaced the full fan assembly and the low speed fan relay. FANS WORK CORRECTLY NOW. No tornado!
Regarding poor cooling complaint: They Checked for leaks, none found, reclaimed system and recharged it. Keeping in mind it was a cooler day here and rain, his initial pressures were 26/275 and after the new fan installation and correct operation he said the pressure went to 26/185.
He initially diagnosed a faulty PCM, but apparently after some discussion with Ford Tech line, so I am told, they determined that the pin out test he was performing was documented backwards, therefore giving him a faulty PCM when in fact it was not. When the pin out was corrected, the PCM tested fine.
So hopefully they will be able to figure out the ac!
Regarding poor cooling complaint: They Checked for leaks, none found, reclaimed system and recharged it. Keeping in mind it was a cooler day here and rain, his initial pressures were 26/275 and after the new fan installation and correct operation he said the pressure went to 26/185.
He initially diagnosed a faulty PCM, but apparently after some discussion with Ford Tech line, so I am told, they determined that the pin out test he was performing was documented backwards, therefore giving him a faulty PCM when in fact it was not. When the pin out was corrected, the PCM tested fine.
So hopefully they will be able to figure out the ac!
Member
Joined: Feb 2013
Posts: 26,680
Likes: 6,253
From: Big Easy
My EXCELLENT NEW DEALER quickly and correctly diagnosed that one of my fans was dead and the other was working on high only when the AC was on. Instead of both on low speed when the AC was on, as it should be. They replaced the full fan assembly and the low speed fan relay. FANS WORK CORRECTLY NOW. No tornado!
Regarding poor cooling complaint: They Checked for leaks, none found, reclaimed system and recharged it. Keeping in mind it was a cooler day here and rain, his initial pressures were 26/275 and after the new fan installation and correct operation he said the pressure went to 26/185.
He initially diagnosed a faulty PCM, but apparently after some discussion with Ford Tech line, so I am told, they determined that the pin out test he was performing was documented backwards, therefore giving him a faulty PCM when in fact it was not. When the pin out was corrected, the PCM tested fine.
So hopefully they will be able to figure out the ac!
Regarding poor cooling complaint: They Checked for leaks, none found, reclaimed system and recharged it. Keeping in mind it was a cooler day here and rain, his initial pressures were 26/275 and after the new fan installation and correct operation he said the pressure went to 26/185.
He initially diagnosed a faulty PCM, but apparently after some discussion with Ford Tech line, so I am told, they determined that the pin out test he was performing was documented backwards, therefore giving him a faulty PCM when in fact it was not. When the pin out was corrected, the PCM tested fine.
So hopefully they will be able to figure out the ac!
I'd like to know what the evap core sensor reading is, if it's within spec then I would start looking for a blend door problem, I wonder if they had the sense enough to check that.
.
Senior Member
Joined: Dec 2011
Posts: 13,811
Likes: 3,184
From: Texas
Is this why my wife's edge and my sons explore produce 39 degree constant air?
Does the expansion valve decide this temp?
Member
Joined: Feb 2013
Posts: 26,680
Likes: 6,253
From: Big Easy
Mine sits at 37 fairly constant.
The TXV provides the orifice which is the restriction in the refrigerant system and separates the high and low pressure sides of the A/C system. As the liquid refrigerant passes across this restriction, its pressure and boiling point are reduced.
.
Member
Joined: Feb 2013
Posts: 26,680
Likes: 6,253
From: Big Easy
The Refrigerant Cycle
During stabilized conditions (A/C system shutdown), the refrigerant pressures are equal throughout the system. When the A/C compressor is in operation, it increases pressure on the refrigerant vapor, raising its temperature. The high-pressure and high-temperature vapor is then released into the top of the A/C condenser core.
The A/C condenser, being close to ambient temperature, causes the refrigerant vapor to condense into a liquid when heat is removed from the refrigerant by ambient air passing over the fins and tubing. The now liquid refrigerant, still at high pressure, exits from the bottom of the A/C condenser and enters the inlet side of the A/C receiver/drier.
The receiver/drier is designed to remove moisture from the refrigerant.
The outlet of the receiver/drier is connected to the TXV . The TXV provides the orifice which is the restriction in the refrigerant system and separates the high and low pressure sides of the A/C system.
As the liquid refrigerant passes across this restriction, its pressure and boiling point are reduced.
The liquid refrigerant is now at its lowest pressure and temperature. As it passes through the A/C evaporator, it absorbs heat from the airflow passing over the plate/fin sections of the A/C evaporator. This addition of heat causes the refrigerant to boil (convert to gas). The now cooler air can no longer support the same humidity level of the warmer air and this excess moisture condenses on the exterior of the evaporator coils and fins and drains outside the vehicle.
The refrigerant cycle is now repeated with the A/C compressor again increasing the pressure and temperature of the refrigerant.
The PCM controls the A/C clutch relay. The evaporator temperature sensor monitors the temperature of the air that has passed through the evaporator core and sends a signal to the PCM. If the temperature of the evaporator core discharge air is low enough to cause the condensed water vapor to freeze, the A/C clutch is disengaged by the PCM.
The line pressure is monitored so that A/C compressor operation is interrupted if the system pressure becomes too high or too low.
The A/C compressor relief valve opens and vents refrigerant to relieve unusually high system pressure.
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During stabilized conditions (A/C system shutdown), the refrigerant pressures are equal throughout the system. When the A/C compressor is in operation, it increases pressure on the refrigerant vapor, raising its temperature. The high-pressure and high-temperature vapor is then released into the top of the A/C condenser core.
The A/C condenser, being close to ambient temperature, causes the refrigerant vapor to condense into a liquid when heat is removed from the refrigerant by ambient air passing over the fins and tubing. The now liquid refrigerant, still at high pressure, exits from the bottom of the A/C condenser and enters the inlet side of the A/C receiver/drier.
The receiver/drier is designed to remove moisture from the refrigerant.
The outlet of the receiver/drier is connected to the TXV . The TXV provides the orifice which is the restriction in the refrigerant system and separates the high and low pressure sides of the A/C system.
As the liquid refrigerant passes across this restriction, its pressure and boiling point are reduced.
The liquid refrigerant is now at its lowest pressure and temperature. As it passes through the A/C evaporator, it absorbs heat from the airflow passing over the plate/fin sections of the A/C evaporator. This addition of heat causes the refrigerant to boil (convert to gas). The now cooler air can no longer support the same humidity level of the warmer air and this excess moisture condenses on the exterior of the evaporator coils and fins and drains outside the vehicle.
The refrigerant cycle is now repeated with the A/C compressor again increasing the pressure and temperature of the refrigerant.
The PCM controls the A/C clutch relay. The evaporator temperature sensor monitors the temperature of the air that has passed through the evaporator core and sends a signal to the PCM. If the temperature of the evaporator core discharge air is low enough to cause the condensed water vapor to freeze, the A/C clutch is disengaged by the PCM.
The line pressure is monitored so that A/C compressor operation is interrupted if the system pressure becomes too high or too low.
The A/C compressor relief valve opens and vents refrigerant to relieve unusually high system pressure.
.
Senior Member
Joined: Dec 2011
Posts: 13,811
Likes: 3,184
From: Texas
Mine sits at 37 fairly constant.
The TXV provides the orifice which is the restriction in the refrigerant system and separates the high and low pressure sides of the A/C system. As the liquid refrigerant passes across this restriction, its pressure and boiling point are reduced.
.