Originally posted by eric1:
Well .. thanks for the info on the vaccuum amount and source .

You indicate it can't be a hand vac, and that it must be 30 in per # maintained for 30 minutes and that the system must hold this otherwise there is a leak. And if there is a leak, the way to detect it (this info you didn't provide in your latest post) is :

1) air pressure and a sniffer ( Expensive shop equipment)
2) UV dye added to R134A and a UV LED pen light ( DIY cheap
method to get by for most larger leaks )

I understand the hand vac is not a 3/4 horse motor with reciprocating piston and valve so the vacuum amount is less, but none-the-less , it is vaccuum and some must be better than none.



Some is not better than none. 25 inches does not remove any moisture. you must get down below 29 inches(mercury) before any moisture will boil off inside and can be removed. 25 inches also leaves quite a lot of air in the system, which will create high pressure in the condenser and reduce the performance significantly of the evaporator.

Quote:

Well when I did hook up the mity-vac, it did hold the 25psi for like 20 min.. I left it and when I came back it was the same vaccuum, so I imagine it heald on the low side.

But you didn't mention anything about using the low side in favor of the high side schraeder valve .... or what is it exactly that the occasion arrises to use the high side port for ?

You check the pressure differentials between the 2 to see if they are according to spec ?_

I have heard people talking about 'pulling ' the stuff f through with vaccuum.. is this what u do to fill the system with the engine off is apply vaccuum at the high side and open a can of R134A applied to the low side ?





The vacuum can be pulled from high or low side, doesn't matter. Compressor off. vacuum is in inches of mercury. 29.9 will get you a dehydrating (Removes water)vacuum. If there is no leaks, but some liquid water, the pressure will still increase somewhat as the water turns to vapor. That's why at least a half hour is necessary. Gives time for all water to vaporize and be removed. After pulling the vacuum, letting it sit and seeing if the pressure rises is a good leak test. Bear in mind, some joints leak under pressure but not under vacuum and vice a versa too. While under vacuum, you add r-134a (liquid, can upside down) while NOT running to low side. Not sure of exact weight, but cans are 12 oz. and the car should have a label saying how much is needed. Use a scale to weigh cans full, then empty. After putting in as much liquid as the system will take (without going over full charge weight), the compressor should be runnable. Add GAS (Can upright) to low side, weighing amount put in, until you have added the correct amount of r-134a. A/C should work great.

There are other ways to do this, but this is the correct way. Other methods may lead to overcharging and damaged components.

Pulling a vacuum, BTW, just means hooking up the vacuum pump and removing the air and moisture from a system. You are "pulling" them out of the system.




My name is Richard. I was a Contouraholic. NOW: '02 Mazda B3000 Dual Sport, Black BEFORE: '99 Contour SE Sport Duratec ATX Spruce Green PIAA 510's, Foglight MOD, K&N Drop-in