Question On air Conditioner system older truck

you need to find out if you can. you'll probably have to do a google. but all of the components will take much more then 2 oz. of oil.

a good thing like one of the posts mentions is to flush. you fill the compononet up with flusher fluid. shake it around. pour it out. blow compressed air if you can to let it dry. then fill the correct amount of oil. using a measuring cup that bakers use.

green seals are what you want. r12 used black seals. 134 uses green seals.

change the orifice or expansion valve. if it has. it's a little screen inside the line. usually the low pressure line and usually at a connection point somewhere.

make sure to evacuate all the air out. both red and blue valves open on the gauges AND on the quick disconnects. then close the valves and let sit for 30 minutes. make sure the evacuation doesn't drop off.

hook up YOUR BOTTLE. and not a can. the reason being is this. you want to open the valve on the bottle. then at the top of your YELLOW line where it hooks to the gauges. crack it open to let the AIR OUT. then close it tight. open the blue valve and let er rip.

always crack open the yellow line to let air everytime you change cans. eliminates all possiblity of air in the system.


YOU HAVE MUCH LESS CHANCE OF AIR GETTING INTO THE SYSTEM BY USING A 30 LB. BOTTLE. THEN USING THOSE 12 OZ. CANS.
a 30 lb bottle can also be had at costco for $115. much cheaper then the cans. and you can fill up much more systems.

charge the system. the low side lines will FREEZE. not just sweat. if properly and fully filled up. freezing lines are more full then line that just sweat. NOW, if you sweat, then freeze. then it starts to sweat again. your over filled. drain some out.

you want the engine bumped up to 1400 rpms. or around there. WITH THE FAN RUNNING.
youi'll charge the system much faster. then just letting the engine idle. you'll have a better reading over idle. specially considering that your engine spends more time driving down the road then idling. by having the fan running. your highside pressure will also be much much lower.

if you turn on the a/c on your front wheel drive. you notice the electric fan is always running.

except that we drive semis and idle a lot compared to cars. but your pressures will be lower then high rpms so there's nothing to worry about.

the general idea for pressure. is low side 20 - 40 psi. the high side on semi's is about 150 psi. the actual theoretical methods is charge the high side to 100 psi plus outside ambient temperature. i've always gone 125 psi plus outside temp. system always blows colder.

the more dumb dumb method would be use a thermometer. (battery operated digital) in the dash and charge till it gets to it's coldest point. once it starts to rise. it's time to shut her down.

disconnecting the hoses. i disconnect the blue side WHILE IT'S RUNNING. pressure is at it's lowest point. more stays in the system and less in the lines. and if your quick disconnect doesn't work. you won't get that big bang and loss of LOTS OF FREON like you do on the high side.

THEN turn engine off. wait for the pressure to drop as far as it will go. BEFORE disconnection the high side line.

and DON'T FORGET. the quick disconnects themselves have a valve. turned in all the way pushes in on the shrader valve in the a/c line. opening the valve closes the shrader valve. you want to close the valves before disconnecting the lines.


that is how i do my a/c. i've been doing a/c since i had my own car. in 1982. i always get 25 to 30 degrees out the vents.
the best i've seen any shop do is 45 degrees.

i was also an auto mechanic during the 90's. r12 was discontinued in 93. we all had to be EPA certified to buy freon. which meant reading a book and passing a test.

and i ALWAYS run the a/c with fan on. specially above 90 degrees. specially when climbing a hill.
a/c don't work too hot when your going really slow up a hill.

your a/c works better when that condensor in the front of your radiator is dissipating the heat.

i have a 97 chev that kicks butt to my 2012 3 month old chevrolet. i'm guess new cars don't get the evacuation procedure as they roll down the manufacturing line.

 

the condensor takes oil. the reciver dryer takes oil which is the filtration system and the compressor takes oil. the evaporator might also take oil but that's inside your dash. that's the little box that blows the actual cold air. just like a heater core.

 

There is a device called thermostatic switch which has a metal probe that goes into the evaporator it has to wires that contols the cycling. There is also a binary pressure switch witch controls if theres to much pressure or too little the compressor will not get power.

 

I just had an issue with the AC in my Pete. Compressor wasn't getting power. It was the thermostat probe in the evaporator.

 

the first and easiest test would be to find the low pressure switch. in the low pressure line somewhere. which is the fatter lines in the system. if the pressure gets below 20 psi it shuts the compressor off. keeps it from burning up by sucking itself into a vacuum state.

that would be the first likely culprit.

that's also why most compressors will cycle off and on when they aren't fully charged.

if you have a 134 system. there should be two high pressure switches. one kicks the fan on when the pressure gets too high in the condensor. the other shuts the compressor off.

134 compressors also have a vent that will release pressure should the 2 high pressure switches not being doing there job. meaning lost freon in the atmosphere.

the second likely culprit would be the actual off;/on swith. or relay if so equipped. and there usually is.

the thrid likely culprit would be that thermostatic probe on the evaporator. which is inside the dash next to the heater core. they don't normally fail that often. unless it's a manufacture defect that could also end up being a common defect or just a bad part on one system.

you can test the pressure switches with a test light. one terminal should have power. then you can use a safety clip or thin wire or something to touch the two terminals. if the compressor kicks on. that's the bad switch. or wiring.

if you got no power then look further down the line.

 

Im sorry i didnt read the post about the pressures the only time ive seen those pressures is when the compressor was bad your system has expansion valve. It would be the first thing i would change. Recharge with proper wight. Those pressures are not right for under or overcharge. Pm me i can speek on phone

 

bingo gear head. he's bypassed the thermostat the trinary or binary switchs or the 2 seperate low and high cut outs and put 12 volts right to the clutch. either the compressor is shot, or the expansion valve, or the orfice tube screen is plugged. all components take 2 oz. oil ( evaporators plural maybe, condensor, rec/dryer, compressor. if you got at least 2 pounds of r134 in the syst. the comp. should pull down into a vacumm unless its worn out , or the valves are not letting freon thru the evap. or is wide open and dumping freon thru the evap. good luck bro!