AC compressor cycling on and off and recharging

Okay check me here: My compressor is short cycling (probably about every 20 seconds or so) and I'm getting weak cool air. So I thought I'd try to recharge the system. Ran the car with AC on max for a while. Hooked up guage/recharge hose to the low side. Am I correct that this is the smaller fitting on larger pipe that's right smack under the shock tower brace on the driver side on an 95 GT?. and The high side is the larger fitting near the radiator on the passenger side that you can't actually get the recharger to fit on? I couldn't it to take more than 2/3rds of a can of 134a before the cheap valve that comes with the kit sprung a leak at the knob. No noticeable increase in coolness (still weak).

Couple questions before I get another valve and can; The gauge that comes with the kit fluctuated as the compressor cycled on and off... it would build up to I think 55psi (mid yellow) then cut on and drop down to the top of the green (about 10-15 PSI I believe). From this I'm supposed to determine the freon charge? Anyway this appears odd to me, shouldn't the compressor pump the PSI UP? When the balancers on the outside of the compressor spin the PSI drops. Should I take the lowest or the highest reading to determine the coolant charge? At no time (accept when the engine was off) did the needle go into the red. Should

2/3rds (maybe less) of a can make some sort of noticeable difference? Or is it likely that something else is wrong (condenser?). The compressor does make a noticeable noise when it spins up (besides the click when it engages) but isn't a bad sound (not a metal on metal sound or whinny). It might be getting tired, but it functions.
Reply to
Simon Juncal
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The fitting that you are connecting to is the low side (suction side) of the compressor. The low side reading is not a good indicator of state of charge. Even using the high side reading in conjunction with ambient temp is a poor indicator of state of charge.

You need to be aware that overcharging can cause system damage..... the compressor cannot handle liquid on the suction side. Brings us to the point about which way to hold the can....... upright gives vapour to the suction side and inverted gives liquid to the suction side.... one way is quick one way is safe.... As the can empties, you'll notice it gets cool to the touch.... wrapping it in a hot towel or warming it with your hands will raise the temperature (and therefore the pressure) of the can.

The large fitting is the low side, the small fitting is the high side (beware, on hot days there can be in excess of 300 psi at this port with the AC running).

In an ideal world, we would have the system recovered and tested to see if the leak is something new and identifiable or if it is just the nature of the beast and has been losing refrigerant too slowly to find. Testing might be as simple as pulling the system down with a vacuum pump (usually a good idea on older units to be sure there is no air or moisture in the system) and then leaving at rest for 20 minutes or so to see if the vacuum drops..... no drop = system good and we can install the proscribed amount of virgin refrigerant.

Of the two methods, one is evironmentally sound and the other is environmental irresponsible..... that's all I can say on the subject.

AC work is relatively easy if we have a good understanding of the basics and what is generally considered as acceptable practices. There are many websites and manuals that will explain the system clearly giving you a much better chance of repairing the system with little wasted money, time and product.

Good luck.

-- Jim Warman snipped-for-privacy@telusplanet.net

Reply to
Jim Warman

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