Recently topped off my r-134. When you guys service your A/C do you completely drain it then refill or just top her off?

 

If you topped it off yourself with a small can of r134A ,then all you want is to" just top it off".It is a waste to empty your system first.,and it introduces moisture into your system which will prevent it from working as efficiently as possible.Moisture is not good overall,for your HVAC. Topping off your HVAC on your own is fine...but follow the instructions.If you discover you are regularly doing this then you are leaking sufficiently and you should have it checked(if you can't find the leak on your own after a visual inspection).

 

the optimal procedure would be to empty it into a container (need special equipment) then pull a vacuum on it which completely removes the moisture, then recharge with some fresh oil, dye and R134a... wait have I done this before... perhaps passed an ASE test?? [8D][8D]


when you pull the vacuum, it should hold around 27-30 inches of mercury worth of vacuum for at least 15 minutes to 1/2 hour without dropping, and then you know it's leak free

 

When you go to a facility for an inspection and your system shows it needs to be topped off,it usually means there is a leak somewhere.It may then require some repair work.If that is the case the freon is removed from the system.After the repair is made,a vacuum is pulled on the system to dry out any moisture(often the desicant is removed and replaced as well).Sometimes the receiver dryer is replaced as well(the desicant is a part of this unit on some cars).After drying the system(30minutes or more)r134A is reintroduced to the system along with a measured amount of synthetic PAG oil(the tech will replace what has been lost).If the cause of a leak isn't found then some U/V tracer oil is added.If the system fails then when you bring back your vehicle the tech will use a blacklight to highlight the leak.A proper repair can be made.Some repairs are nothing big (a schrader valve) and others may mean the replacement of a component.

 

Thanks for the info. The reason I was asking is because when I bought the car. My DD a 2000 Taurus. The AC wasn't getting as cold as I liked. So I went and got a can and added what I could ..using guages...so that it didn't have too much pressure. It blows COLD but was wondering if I should have just drained it all and put in the oil and r-134, thanks for info again before I screwed it up. Only thing it tends to do now is it seems that the compressor is cycling on and off durring the first 10 15 mins on my way home....not fast but every so often. Not a big deal.

I assume that the quality of the r-134 in the system would not cause the comprssor to cycle on and off. But from lack of pressure, which I donot have. I am thinking this is the same r-134 in it from the factory.

 

The quality of R134A should be the same.There may be some moisture in the system?Theres a whole lot if things that can cause your system to cycle on and off too often.Take the temperature from one of your airvents(do it while reving the engine at 2 grand).It should read about 45to fifty degrees at the coldest setting).If your car has a sight glass look and see if there are bubbles in it.There should not be any(afew tiny ones are okay).Time the cycling on and off ...doors and windows closed...and record it.If you are low on your charge it will cycle more often, and for longer duration.It won't cycle at all if your empty.You also get a tendency of a freeze up on your evaporator if your low...You will then get warm and cold air alternating in the car.You may have a clogged orfice tube(don't laugh , I'm serious).If you are sure you have no leaks and you are just low on your charge try adding a bit more R134A.