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A/C Techs Help Needed

854x4 on Wed May 21, 2008 11:17 AM User is offline

Year: 1986
Make: Toyota
Model: Truck
Engine Size: 2.4L
Refrigerant Type: Freeze-12
Ambient Temp: 100+

My a/c quit blowing cold 50 degree vent and now only blows cool 70 degree vent. So I hooked up my gauges and I'm getting 40 on the low and 250 on the high, when I rev it up to 2,000 the low goes to 10-20 and the high goes to 300-330 all the lines are hot except the one from the compressor low side to the expansion valve. Also my expansion valve use to make a hissing noise and now it doesnt. Now heres the part I dont understand when I shut off the a/c the pressures dont equalize the low goes to 90 and the high goes to 250. I think the expansion valve maybe bad or there is a restriction somewhere in the system. Also I converted the system to freeze 12 last year and it worked fine for the whole summer and up untill last week. Yes the system was properly evacuated and recharged to the proper amount and the sight glass shows the freon moving just like it should. Here is the weird thing it did the same thing last year, the expansion valve quit making noise and the a/c quit blowing cold so I replaced the drier pulled vacuum on the system and recharged and the expansion valve started making the hissing sound and the a/c worked great. So I think I may have to replace the expansin valve flush the evaporetor pull vacuum and recharge. Also does anyone elses expansion valve make a hissing sound my 85 also does it with a full charged R12 system and it works great. One last thing if I put the controls on recirculate it starts to cool better but not like it was. Any Thoughts?

Edited: Wed May 21, 2008 at 11:25 AM by 854x4

mk378 on Wed May 21, 2008 1:34 PM User is offline

Make sure the heater core isn't reheating the air. How cold does the suction line get?

You may have high high side because the fan clutch is worn out. Spray water on the condenser and see if it drops a lot. Having poor condenser airflow at idle will raise the pressure and mask the fact that it is also undercharged.

If it is fully charged and has a pressure of 20 on the low side it should be cold inside. If not, the expansion valve could be bad.

Sometimes expansion valves make noise and sometimes they don't, it doesn't mean much. It's also normal for the pressures to stay unequal for a long time after the compressor stops on a TXV system.

Freeze-12 is basically R-134a with a HCFC ingredient to move the oil around. You could get similar performance with pure R-134a, after changing to ester oil of course.

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