hi all, i have a 2000 quad cab with a 4.7L and 185,000 miles. my AC blew cold for the first couple of years that i had it. then, 2 years ago, i had to put a can of R134a in it because it was never cold. after that, it was cold all summer long. then, last summer, it stopped being cold again, so i put another can of R134a in it. that's when it started acting weird. it would be cold for probably 10-15 minutes, and then just turn off (air temps got warm) and stay off. it sometimes would eventually come back on it's own a while later, but usually i would have to turn off the AC **** and wait 10 minutes or so, turn it back on, and then it would blow cold again...for awhile. i just dealt with it for the remainder of last summer, but now that it's starting to get warm outside again and it is still doing the same thing, i want to fix it properly this year before it really starts to get hot outside

do you think i am underfilled for R134a? overfilled? something else?

(fyi, i used a gauge both times i added refrigerant...but it was the super cheap gauge that comes with the can, so who knows if it is accurate)

 

You need a gauge set, not just one gauge to really get an idea as to how your a/c system is working.

Odds are you are just low but without BOTH the high and low pressures you can't know. There may be another problem with the system. Maybe your local parts store will rent/loan a gauge set.

Dye can be added so that you can find any leaks using UV light.

 

Whats the psi when on? if it has a separate condenser fan make sure its coming on-

 

i'll have to check the psi when i get a chance, but regardless of the electric fan coming on or not, it stops working while driving on the freeway (no fan needed at that speed, plenty of ram air going through the condenser)

 

It sounds like its over charged let some Freon out and see what happens a little at a time and be very careful Freon is dangerous to the Human body and can blind you if sprayed in the eyes.

Use eye protection

By the way its illegal to do this don't let anyone see you do it this way.

I flop a hand towel over the valve hold it down as it can blow up on you then use a screwdriver to depress the valve and let some out.

The towel deflects the Freon down away from your face

With the engine off

 

freon is R12. R12 is the really horrible stuff that will hurt humans and the environment. mine (like everything else over the past 20 years) is R134a. it's not that bad. (not that i'd suggest breathing it) :-)

i did pick up a gauge set today, so i'll try it over the weekend to see what happens. i'm also wondering if my pressure switch went bad...but one step at a time.

 

A little off topic - R134a is worse than R12 in some aspects. It has a high "global warming potential" and has been banned by several countries.

 

well, that won't be a problem much longer anyways. the industry is in the process of switching to R1234YF...which doesn't work as good, but is less potent.

 

i checked my AC. looks like with it off (when the compressor won't cycle), it is 70 psi on the low side and 75 psi on the high side. with it cycling, it is between 17-43 psi on the low side and 90-130 psi on the high side. here's the thing though, the gauge set was leaking when i first plugged it in (one of the hoses was loose). i have no idea how much i lost, but regardless, from the numbers i got AFTER i plugged it in (after fixing the hose leak), i'd say i'm low on refrigerant. agree?

how much refrigerant do you think i'll need (should i buy one can or 2)? is there a rule of thumb for "good" pressure when i'm done? (tomorrow is supposed to be around 65°-70° tomorrow...i know the pressure range changes with temp).

 

At 70, per the factory manual:

Low Side: 25-35 psi
High Side: 160-200 psi