A/C problem
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From: Fort Worth
A/C problem
The A/C doesn't work. When it is switched on, the compressor will cycle on/off every 3-4 seconds. All hoses stay warm. I have recharged it, but it never changes anything. When the truck is off, the gauge reads 33 psi. With the truck running and A/C on, the gauge goes up to around 38 or so and then the compressor cycles off so down to 15 or so, cycle on and back up to 35-38, repeating. What could be the problem? Thanks.
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From: Mattawa Washington.
What truck are you recharging? R-12 or 134A? It that the low side or high side pressure. Sounds like you are not getting freon into the system but more information is needed to be of more help..
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From: Fort Worth
I replaced the high pressure switch located on the dryer up top, but I noticed another electrical connector down by the compressor itself, what is that? Any info anyone needs to solve this, just ask.
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From: Scio, OR
This is what the service manual for a 2004 says.
A/C Cycling Switch
The A/C cycling switch is mounted on a Schrader valve-type fitting on the side of the suction accumulator.
* A valve depressor, located inside the threaded end of the A/C cycling switch, presses in on the Schrader valve stem.
* This allows the suction pressure inside the suction accumulator to control the operation of the A/C cycling switch.
* The electrical switch contacts open when the suction pressure drops, the contacts close when the suction pressure rises.
* When the A/C cycling switch contacts close, the A/C request signal circuit is completed to the PCM.
* When the A/C cycling switch contacts open, the A/C request signal circuit is interrupted and compressor operation stops.
* The A/C cycling switch will control the A/C evaporator core pressure at a point where the plate/fin surface temperature will be maintained slightly above freezing.
* This prevents icing of the A/C evaporator core and blockage of air flow.
* It is not necessary to discharge the refrigerant system to remove the A/C cycling switch.
Dual Function Pressure Switch
The dual function pressure switch (DFPS) is used to interrupt A/C compressor operation in the event of high system discharge pressures.
* The dual function pressure switch is mounted on a Schrader valve-type fitting on the high pressure side of the compressor manifold and tube assembly.
* A valve depressor, located inside the threaded end of the DFPS, presses on the Schrader valve stem.
* This allows the DFPS to monitor the compressor discharge pressure.
* The DFPS has two sets of electrical contacts. One set of contacts is normally closed and is used for A/C high pressure cutoff.
* When the A/C compressor discharge pressure rises, the switch contacts open, disengaging the A/C compressor. When the compressor discharge pressure drops, the switch contacts return to the closed position, and A/C compressor operation resumes.
- The second set of electrical contacts in the DFPS is used for engine cooling fan control.
The A/C cycling switch is mounted on a Schrader valve-type fitting on the side of the suction accumulator.
* A valve depressor, located inside the threaded end of the A/C cycling switch, presses in on the Schrader valve stem.
* This allows the suction pressure inside the suction accumulator to control the operation of the A/C cycling switch.
* The electrical switch contacts open when the suction pressure drops, the contacts close when the suction pressure rises.
* When the A/C cycling switch contacts close, the A/C request signal circuit is completed to the PCM.
* When the A/C cycling switch contacts open, the A/C request signal circuit is interrupted and compressor operation stops.
* The A/C cycling switch will control the A/C evaporator core pressure at a point where the plate/fin surface temperature will be maintained slightly above freezing.
* This prevents icing of the A/C evaporator core and blockage of air flow.
* It is not necessary to discharge the refrigerant system to remove the A/C cycling switch.
Dual Function Pressure Switch
The dual function pressure switch (DFPS) is used to interrupt A/C compressor operation in the event of high system discharge pressures.
* The dual function pressure switch is mounted on a Schrader valve-type fitting on the high pressure side of the compressor manifold and tube assembly.
* A valve depressor, located inside the threaded end of the DFPS, presses on the Schrader valve stem.
* This allows the DFPS to monitor the compressor discharge pressure.
* The DFPS has two sets of electrical contacts. One set of contacts is normally closed and is used for A/C high pressure cutoff.
* When the A/C compressor discharge pressure rises, the switch contacts open, disengaging the A/C compressor. When the compressor discharge pressure drops, the switch contacts return to the closed position, and A/C compressor operation resumes.
- The second set of electrical contacts in the DFPS is used for engine cooling fan control.
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