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I just bought a 12oz can of r134 to recharge my a/c i hooked it up and sure enough the compresssor kicked on and it sucked the can dry. but do i need to get another can? logic would say that once the system is full it wont take any more and stop letting the system take any from the recharge bottle. Is my logic correct? :lecture:
hmm i can't remember the ounces...but it was 2.5 - 3 "short" cans to fill the average system. And to answer you logic question, NO, you can definitely over fill the sytem causing the compressor to fail early. Best thing to do is get you the $10 gauge from discount and add until its in the green..I wanna say around 20ish psi...
YES you can overfill the system. The refrigerant will flow into the compressor. Compressors only compress GAS. not liquid. liquid is incompressible.
Second, An A/C system is based on MASS FLOW of refrigerant. So in otherwords basically you can't pump a pressure into the system and expect to know how much refrigerant is in there.
the pressure reading on mine was around 40 psi. and It didn't go up or down based on how much i pumped into the system. I put less than a can because i didn't want to botch the compressor
IF however you get your air working properly, tell me how man cans of the stuff you put in, so I can do the same. haha
pump a pressure? I'm lost.... If you add more cans your pressue will indeed go up, if it doesnt then you have a leak. the A/c System works by the expansion and compression of gas...Your compressor takes gas from the low side and compresses it out the high side. You need enough pressure on the low side for the compressor to even kick on. Get the gauge it will tell you if you need to add more...looks like a garden hose nozzle. And I was off on my number it should be around 30-45ish on the low side... to do it properly you need to have your a/c on full blast. And check the pressure once the compressor kicks on, this will tell you how much pressure you have with the comp. draw.
THANKS! well, like i said, as soon as i started to fill the system the compressor kicked on so the pressure switch read enough pressure to let the comrpessor turn on. i guess i will just run it as it is and see what happens.
yea if it kicks on then you're fine...but the system has a "sweet spot" psi range that is the optimum efficiency for cooling, so if it still isn't cold enough you may need to add a little more.
yea if it kicks on then you're fine...but the system has a "sweet spot" psi range that is the optimum efficiency for cooling, so if it still isn't cold enough you may need to add a little more.
And there's not much "play" in this sweet spot either....too little freon, and it will blow warm....too much freon, and it will also blow warm.
This is why a/c repair/recharges are not as easy as most think....they're very easy to screw up, and it's really best to have a full set of guages that read both high and low pressure when you're adding.
However, since yours kicked back on with one can, I would run it like that and see how it does. If it's still cycling on and off too much (I believe the FSM states anything over 10 cycles in under a minute....but I could be wrong about the number) you might try adding a little more...but for right now, i'd probably leave it.
edit: Also make sure you have it set on MAX (recirculate) and the fan speed set to 4 when you're adding freon.
yes what i was saying about the pressure and mass of refrigerant in the system -- you won't know the mass of refrigerant in the system by putting a certain pressure into the system.
so i am agreeing with you guys - there is a fine line between too little and too much refrigerant and the gauge on these 20 dollar top off kits is not accurate.
that's why the guys at the shop always say dump the system entirely and put all new refrigerant in - because by doing this they are able to measure precisely how much refrigerant they have inserted into your vehicle's AC system.
once again - refrigeration systems are based on mass of refrigerant, not based on pressure of refrigerant in the system.
yea I have no problem building engines and drivelines, but when it comes to a/c I take it to a shop...When I got ase certified for engines I thought about going for a/c too, and then took one look at the book and said "yea I'll just move north when mine breaks".
A/C is more simple than you think, once you know the flow of refrigerant in the system and the evaporation and condensation of the refrigerant it is so easy. I wouldn't recommend anyone try to fill their system with can's of refrigerant, if it's low, it's leaking somewhere. Just take it to a local repair shop to get it fixed right. And hey, they also have a warranty on parts and labor. Just my two cents.
The good shops like to empty the system and change the drier. They should be able to estimate the freon charge pretty well by simply looking at the high and low side pressures. The FSM calls for 32 oz, so 2.5-3 of the 12oz cans is about right. I'd probably dump another can in and call it good. If it was low enough to stop cycling it was probably almost empty.
Personally, I have a slow leak in the ZJ and I dump in a $5 can of R134 at the start of each summer. Much cheaper than finding the leak, which is probaby in the core in the dash.
Hopefully I'm not too late for this thread. I have the opposite issue. My electric fan is not coming on all the time. I allways thought the fan came on whenever the a/c is on. Apparently the newer (2000) XJ have a "dual" mode high presure switch. One of it's functions is to turn on the electric fan at the correct high side presure. I have minor experience with a/c systems and am not sure how to diagnose this. I do know that when the fan is on my presure at 90 F is 300 high, 47 low. These are from the field manual. At this presure the electrical fan will start cycling and then the presures really get high and the system does not cool. I have to get this fixed as it lock up this weekend and burnt the belt and maybe the clutch.
Anyone have this high side switch go bad? I wonder why they just dont have the fan relayed to the a/c symply?
From the 2000 FSM:
===
Electric cooling fan 4.0L:
With or without A/C request the electric fan will come on only when the coolant temperature is at least 106° C (223° F), and will remain on until the coolant temperature drops to 103° C (217° F) or below. Regardless of coolant temperature, When air conditioning system pressures reach 300 +/- 20 psi the electric fan will engage and continue to run until the A/C system pressure drops to 235 psi minimum, then the electric fan will shut off.
===
IF your system is so low on refrigerant that the compressor clutch will not engage or runs briefly until the system pressure is too low or evaporator temperature nears freezing... then you should really have it serviced to locate the leak.... (ie. pump out all refrigerant, pull system into vacuum, add leak detecting dye and search for leak with black light).
Another way to locate leaks would be to look for tell tale dirt build up or oil seaping from O rings, schraeder valves or compressor shaft seal....
IF your compressor cycles continuously.... (more than 10 times in 1 minute) then you in need of refrigerant. You have enough refrigerant to cool the incoming air, but not enough that the air will be cold....
With outside air of 80*; the air coming from the vents should be about 50*. When charging the system without knowing what quantity of refrigerant remains...; you can add small quantities until you see the discharge air drop several degrees while watching the drier and the incoming/outgoing lines....
The lines should be cold to the touch (40*) and maybe some sweating, but not frosted....
General rule of thumb for suction pressure should be 30-35 psi and discharge pressure should be 215-225 psi.... which should give you cold air without being over charged....
I just bought a 12oz can of r134 to recharge my a/c i hooked it up and sure enough the compresssor kicked on and it sucked the can dry. but do i need to get another can? logic would say that once the system is full it wont take any more and stop letting the system take any from the recharge bottle. Is my logic correct? :lecture:
No that is completely wrong, it is very possible and very easy to overfill an ac system.
If yours was factory R134, you need 1.25 pounds (20 ounces) of refrigerant and 6 ounces of PAG 100 oil.
If yous was factory R12, you need about 85% of system capacity in r134. Do not go by the old "clear sight glass" method. You need around 6-8 ounces of Ester oil.
I hope you got the system vacuumed out and possibly flushed before you started. If you did, congrats on getting your AC to work.
If it was not flushed, there may still be a good amount of oil in the system. This could cause problems, as it could be moisture contaminated (pag and ester are hygroscopic, water-attracting) and you will have a hard time figuring out how much is in there. Remember, more oil equals less refrigerant.
To remove the majority of the oil.... you can blow it our with compressed air and the purchase a oil flushing chemical to remove the residuals....
When you purchase the retrofit kit...; they should have the chemical available...
Sorry.... Cant remember the name of the flush....
