I am new to forum. I have read previous posts about AC problems on here. So here is my situation and done things and then the questions. The AC in my 2001 F250 just stopped. All fuses etc are checked and good, What I found by shorting the low side pressure switch is that the clutch engages, When I put an A/C recharge can and gauge on is that without the ac running The dummy indicator is in the yellow zone. As soon as I cross the low pressure switch the dummy gauge goes to zero. I put some freon in while the A/C was on high and blower on high and the needle didn't really move out of that area but when I turned the A/C off the low pressure gauge reading was approaching the red zone, actually in it. Now after hooking the actual pin switch on the low side back up it is actually cycling back and forth pretty rapidly. Question should I continue to put freon in with A/C on high and blower on high until the gauge reads good???? I know I am concerned on the actual low side reading but where should the dummy gauge read when everything is off or should I not be concerned with that reading. I don't want to implode the system. The pipes leading to the ac in the cab are not cold at all Insight please FL is hot all yaer LOL Thanks Skip

 

Short answer: Yes, keep putting refrigerant in until the dummy gauge is in the green zone while the clutch stays engaged. Add a little at a time and avoid overfilling.

Long answer:
Understanding how the refrigeration cycle works is essential to knowing why the system behaves the way it does when you do certain things to it. The Tech Folder sticky at the top of this forum has an entire HVAC section dedicated to this. I suggest you start with this document which can be found in the Tech Folder.

Basically, the reason your clutch only engages when the low-pressure switch is shorted is because that switch is there to prevent your compressor from spinning and burning up when the system is low on refrigerant. When you shorted the sensor's wires, you tricked the system into engaging the clutch. Then you added some refrigerant into the system which gave the low pressure sensor some refrigerant pressure to sense, those closing the circuit and engaging the clutch. Once the clutch was engaged, the compressor ran and the suction side sucked whatever refrigerant there was into the compressor until the pressure dropped so low the low pressure sensor opened the circuit again. This disengaged the clutch which stopped spinning the compressor. Refrigerant then flowed out of the compressor, through the condenser coil, through the orifice tube, through the evaporator coil an then finally back to the low pressure sensor. Once enough pressure built up at the low pressure sensor, it closed the circuit and reengaged the clutch. Rinse and repeat.

I think it is important for you to find out why your system is low on refrigerant instead of just pumping more in. Simply adding more refrigerant is not a long-term solution. Also an AC system that blows warm is not necessarily low on refrigerant. The symptoms you describe are consistent with low refrigerant levels however.

 

what he said!!!! Find the leak!!

 

nope he has a clog in the line. mind you this is only my thoughts.. but his screen name is sperm1952...which indicates he is no longer viable. just laughing my *** off...

ken

PS Dude I honestly hope you are not pissed by this reply.. but everyone needs a nickname.

 

Somebody's been day drinkin again, or is it night there. Either way hide the credit cards. Don't want to wake up w/ a new mortgage.

 

or strippers i don't know!

but honestly a clog in one of the lines would cover 90% of what he is experiencing a solid no BS flush with a new dryer and expansion chamber would do wonders.

 

Oh come on now. You know you had a fun night when you wake up and find glitter in all the right places.

 

hey stop that...my wife will get the wrong idea!