My AC just stopped working. I replaced fuse and Wide Open Throttle relay. Still no go. Checked and added refrigerant, still no go, even though it cycled on and off for about ten times. Connected battery directly to compressor, it engaged and cooled the truck. Someone said the low pressure swith maybe faulty. Any ideas?? Can I bypass the switch and check it. Can I change switch and not evacuate system?? Any ideas would be appreciated.

Liltruck

 

Fixed it!!!!! Went to NAPA bought a low pressre switch,($25) took the old one out by hand twisting and put new one in. Works like a charm.

liltruck

 

I'm having A/C problems too and have gone through fuses, relays and refrigerant as well. I'm still trying to figure it out. What was your HVAC doing when you were having the problem? Thanks.

 

liltruck:

Did they pull a code to know or was it a short in the dark? Is that monitored by the OBD - OnBoard Diagnositcs? If they pulled a code, what was it?

 

No code was pulled. The compressor was simply not engaging so I first checked the plug on the compressor and no voltage was getting to plug. I then checked fuses and relay. All were fine. I checked the refrigerant with an Auto Zone kit and levels were fine. I then went to low pressure switch and did a voltage check. 12 volts was coming in and 2 volts was going out. I was told that if everything was working right 12 volts should be going out which should then turn the compressor on. I replaced the low pressure switch and everything worked!!!!

Liltruck

 

jt-stl,

Don't know what the HVAC is.

Liltruck

 

Sorry, just short for Heating Ventilation and Air Conditioning system. I get nothing but the hot air you would expect when it's dialed to the hottest setting, even when I have it on max a/c and set at the coldest setting. Same with all other combinations and settings. Air's always hotter'n hell. I get no codes, there's no info stored in the computer about, no noticeable vaccuum problems. I was hoping you had similar symptoms so that I could be optimistic about getting off cheap for once

 

The compressor was simply not engaging. When I would turn on the AC, the compressor would not engage and thus no cool air would come out. I first checked the plug on the compressor and no voltage was getting to plug. I then checked fuses and relay. All were fine. I checked the refrigerant with an Auto Zone kit and levels were fine. I then went to low pressure switch and did a voltage check. 12 volts was coming in and 2 volts was going out. I was told that if everything was working right 12 volts should be going out which should then turn the compressor on. I replaced the low pressure switch and everything worked!!!!

Liltruck

 

liltruck:

I am experiencing same problem with my a/c in my ranger. Sorry for the stupid question but can anyone tell me where the low pressure switch is located?
Thanks in advance.

Karslake

 

I have a 4 cylinder. Looking at the engine the switch is on the left side. Start with the compressure and follow the the hose from it that goes to the left. You will see a black and silver thing that kinda looks like a spark plug with wires attached to it. That is it. I unplugged it and twisted it off by hand, twisted the new one on and replugged it. There is a similar item on the right side of the compressor. I think that is the high pressure switch. Good luck.

 

Hi liltruck,

When you replace the pressure switch, did you release any coolant or freeon?

Did you have to recharge freon?

Thanks in advance.

P.S. Mine is a 2000 Mazda with a 2.5 four and the same symptoms. (see my new post)

 

hey lil... tell us a little about ur truck... year, model, motor etc... I'm having roughly the same problems in my '91 Ranger 2.3L. Perhaps this could be a quick fix for me too, but I dont know what kinda truck you have (year).

 

Hi Liltruck:

Well I did what you said and as I was untwisting the low pressure switch a lot of pressure plus a green liquid began to oozze out, so I quickly tightened it back as dreaded it may well be the cooling gas Freon. Maybe it is low on this gas and maybe because of this the AC is not working. As you said your compressor began to work but does it cool?I think I´ll take it to a specialized shop to see if the can help me cheap. Perhap I may get away with a re-fill? after all it has never been recharged in 7 years.
Cheers Karslake

 

After the low pressure switch was replaced the AC cooled like a champ and is still doing fine. In reference to losing refridgerant, when I twisted the valve off, there was an instant pressure release but no significant loss of any refridgerant. The base of the switch has an o ring and the new switch has a new o ring which I believe keeps the freon from escaping. I am not familiar with other switches and don't know if they are different or not. My truck is a 96 with the standard 4 cylinder. I am pretty careful around AC repairs and would recommend bringing your problem to a pro. if you lack familiarity with the needed repair.

 

karslake, I think you may have pulled the temp sensor for the cooling system instead of the low pressure cutoff switch for the HVAC... I don't remember anything in the HVAC system being green... But Antifreeze is!!!