AC only blows hot air, '10 Taco

My 2010 Tacoma reg cab 4WD 4CYL man trans USED to have ice cold AC but suddenly it's nothing but hot air. First I replaced the cabin air filter (very dirty) but nothing has changed. I researched the issue in this forum and have diagnosed it (so far) to my compressor clutch not engaging. The AC light is on constant (not blinking) as is the recirculation light. I have visually examined the compressor clutch and sure enough, it's not spinning regardless of the AC light on or off. The system, when it worked, used to emit a noticeable sound when the AC was engaged but no sound anymore. I'm open to replacing the compressor myself with a new aftermarket one (GPD with condenser) for around $250-$300 and then have the system vacuumed, re-charged and inspected. Does this sound about right? Additional info: 30.5K miles, never had a problem before, very reliable truck. I can turn the compressor easily by hand, seems very solid, no clearly visible problem, no leaking grease, etc. Thanks in advance from all!

 

Well if the compressor is not engaging, the first checks should be electrical not refrigerant. The computer controls compressor clutch engagement. There is a low pressure switch, could have gone bad, or it actually could be low on refrigerant. Since it worked fine before, then it sounds like something electrical went south.

 

Did you happen to disconnect your battery for something prior to this? My AC does this every time after plugging back the main battery after a disconnect. It always cleared itself up after a day or so. I don't know why and don't bother to find out why either

Not a fix, just sharing my experience.

 

Thanks for the replies!
My battery has not been disconnected recently so I don't think that's the issue. I agree that it is likely electrical but WOW what a PITA to track that down. I'm going to try to go through every electrical component to try to find if it is a faulty or failed part; any suggestions on where or how to start are appreciated!

 

#1 check for power at compressor clutch, if none
#2 find and check low pressure switch, if closed
#3 find wiring harness from computer and check if computer is sending power to compressor clutch
These are the obvious steps, then look at ac controls, thermostat etc.

 

Thanks so much for the advice bchannell! I'll get on it tomorrow!

 

OK; I found out that the compressor clutch is OK; I applied 12V power to the wire lead and it closes normally. I visually examined the 'pressure switch' (located on the HP line just before the entryway to the condenser) and it appears almost like new; hard to believe that this solid state 'switch' would go bad (If anyone knows the procedure for checking this switch electrically please let me know). I'm now thinking that the system pressure has dropped (probably due to a leak somewhere) so I'm planning to acquire a set of gauges to check the system pressure. Assuming that the pressure is out of standard I'll apply vacuum pressure for 45 minutes, then see if the system will hold a vacuum for 20-30 minutes or so. If that works, I plan to add 12-22 oz of R-134A refrigerant, along with about 3 oz of PAG oil to the system and see where that gets me. All lines look undamaged and the compressor and clutch appear to be working normally. Knowledgeable opinions about my plans is encouraged, thanks in advance!

 

1. Go easy with the oil. It only rarely leaks out. Too much can cause as many problems as too little, even more.

2. 22 oz is the correct amount. And you can actually get by with using two 12 oz cans, as the hoses will hold some themselves. When I recharge one of these things, 2 cans works well.

 

Thanks for the input Robert, you're the one person I was hoping would check in here! I plan to have two (2) 12-ounce pure R134A cans available when I re-charge the system, and anticipate using at least one can, and possibly most of a second can to achieve a 22-OZ fill. I guess, based on your advice, I'll limit the oil to 1-2 OZ and hope that will do it. Thanks for the advice!