1997 AC question
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From: Oswego
1997 AC question
97 Expy, 4.6. AC was doing fine. Go away for a week, come back, AC doesn't work. From what I can tell, the clutch is not engaging when AC is turned on. Is there an AC clutch switch or something? Will the clutch not engage if refrigerant is low?
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clutch should engage no matter if there is coolant in there or not (we used to use AC compressors on jeeps as an air compressor, so no coolant at all 
)
if you can locate the compressor, there is a power lead going to it. 2 things to try -
1 - try and "bump" the compressor on by hotwiring 12 volts into it with a jumper wire (engine off of course!) this will tell you if it's the switch side or the compressor side.
2 - with the ignition on but engine off, turn on AC and see if there is voltage at the compressor - this will tell you if it's the switch side.
Offhand I couldn't tell you what fuse to check, and I can't reach my manual at the moment.
)if you can locate the compressor, there is a power lead going to it. 2 things to try -
1 - try and "bump" the compressor on by hotwiring 12 volts into it with a jumper wire (engine off of course!) this will tell you if it's the switch side or the compressor side.
2 - with the ignition on but engine off, turn on AC and see if there is voltage at the compressor - this will tell you if it's the switch side.
Offhand I couldn't tell you what fuse to check, and I can't reach my manual at the moment.
Fleet Owner
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Say what????
There is a low pressure cut-off switch that disables the compressor clutch when the refrigerant pressure (on the low side) drops below 22 PSI.
There is a low pressure cut-off switch that disables the compressor clutch when the refrigerant pressure (on the low side) drops below 22 PSI.
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Fleet Mechanic
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From: Lorain County, Ohio
Try these 2 simple checks with the engine running and the AC on:
-Carefully tap the face of the compressor clutch with a dowel or screwdriver handle.
-If the clutch engages, the clutch gap is too wide. It can be easily adjusted.
-If the clutch doesn't engage, locate the Low Pressure Cutout Switch (Cycling Switch). It's a 2 wire switch on the accumulator "can" near the firewall. Disconnect it and jumper out the connector with a piece of wire or paper clip.
-If the clutch engages, the switch has failed or the system is low on refrigerant due to a leak. You'll need gauges to check the system pressures and determine which.
-If the clutch doesn't engage, there is likely an electrical problem and more testing is needed.
-Carefully tap the face of the compressor clutch with a dowel or screwdriver handle.
-If the clutch engages, the clutch gap is too wide. It can be easily adjusted.
-If the clutch doesn't engage, locate the Low Pressure Cutout Switch (Cycling Switch). It's a 2 wire switch on the accumulator "can" near the firewall. Disconnect it and jumper out the connector with a piece of wire or paper clip.
-If the clutch engages, the switch has failed or the system is low on refrigerant due to a leak. You'll need gauges to check the system pressures and determine which.
-If the clutch doesn't engage, there is likely an electrical problem and more testing is needed.
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From: Oswego
so...
I pulled that plug off the pressure switch onthe accumulator, jumped the connector and the clutch went on. How does that switch come out of the accumulator? The pics of new ones online do not show any threads, so does it thread on or is it a plug? You say that still might mean there is low pressure (leak) though, too, correct? Thanks for the help.
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From: Oswego
update
SO i plugged the connector back into the switch, thinking maybe it was a bad contact or something. NOW, the clutch will engage for 5 seconds, then disengage. 15 seconds later, engage for 5, then disengage. I can hear the switch "switching". This leads me to believe that the pressure is low, and the switch turns on but there is not enought pressure to hold it. Is my thinking correct? I don't have gauges to check the system pressure.
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Lead Driver
Joined: Jul 2007
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From: Rhode Island
The pressure switch is a pseudo temperature control to stop the evaporator from frosting up. Temperature is related to the pressure difference on air conditioning system. So Ford adjusts the pressure switch, at about the same pressure on the low side of the system, where the evaporator is just above the frosting point.
Short cycling like that indicates that there is not enough refrigerant in the system, as the low side pressure gets pulled down very quickly
Short cycling like that indicates that there is not enough refrigerant in the system, as the low side pressure gets pulled down very quickly
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Fleet Owner
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Yes, your thinking is correct.
Fleet Mechanic
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From: Lorain County, Ohio
The low side port should be on the accumulator itself or somewhere on the large hose returning to the compressor.
If you have "gauges" the red high side hose will connect to the port that you found.
If you have "gauges" the red high side hose will connect to the port that you found.
Fleet Mechanic
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From: Lorain County, Ohio
For my own knowledge, is it on the accumulator or on the suction hose? I don't remember on those trucks.
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From: Oswego
found it
Put the gauges on, and the pressure was going down to about 20, then would build to about 40, clutch would engage, go back down quickly and clutch would disengage. Put in a can of coolant with stop leak and dye, we'll see how long it takes and if I can find the leak. Thanks for all your help! Could it still be the switch not being able to hold? With thte charge in it, the air is blowing cold now, but the clutch still seems to be cycling as opposed to staying on.