Project 97: Re-Charging the A/C System - possible to over-charge?

[Matt at Dunlop]

After fixing the aux-fan in my E36, the A/C still wasn't quite as cold as I thought it could be. I bought a $39 kit from the parts store that comes with a gauge to measure pressure on the low side port, and 2 cans of R134a to add to the system.

I measured 25psi on the low side port (~75deg ambient temp) The pelican parts 101 projects book and the gauge that came with the kit both recommended ~45psi for the system to run optimally. Well, it took both cans of refrigerant in order to get to 45psi on the low pressure side.

Now...my compressor makes some not so normal noises, switches on & off constantly, and doesn't really blow cold at all.This leads me to the following questions....

* Is it possible that I OVERcharged the A/C system with 45psi in it??
* What are the potential dangers of an over-charged system??
* How do I relieve pressure from the system?? Can I drain it somehow and start over??

I've searched & found a few posts about "pulling a vacuum on the system and then recharging it", but all of those posts seem to use that phrase as an expression...no one really explained what that meant or how it was done.

Any help would be appreciated!!!

Thanks in advance,
Matt
Edit/Delete Message

[dboyles]

That definitely sounds like the system is overcharged (compressor kicking off and on, not blowing cold). You can verify this with a gauge (you'll see the pressure building, then the compressor will cut out and the pressure will drop). Although not legal, you technically could lower the pressure using a screwdriver to open the valve on the low side. The better option would be to take it to a pro. I am a DIY person all the way when it comes to my car with the exception of A/C work. For that, I pay somebody to do it right.

There shouldn't be any permanent damage to the system, but you should avoid running it if possible.

[Bear]

Think freezing (+32 F) and keep the low side around 32 to 34 psi (HFC 134a).