AC question

[JonE]

My '90 535iA AC doesn't blow cold at the moment. I took it to an indy that found around 50PSI on the system with his guages. One question is whether there is a site glass on this E34 (there is on my '89 325i)? Second question relates to proper AC system psi and whether a low pressure switch is inactive if the system is too low? This indy says I can take a chance and throw a pound of expensive R12 in to see if it works but that it could be something else. The compressor does not come on when the AC button is pushed in.
Anyone know anything about this, please?
Jon

[Bill R.]

car up by the firewall... and 50 psi is not enough pressure in the system to turn on... Its low on freon. I'm assuming that you mean 50psi static with the car off.... and an ambient temp outside of at least 80F...






My '90 535iA AC doesn't blow cold at the moment. I took it to an indy that found around 50PSI on the system with his guages. One question is whether there is a site glass on this E34 (there is on my '89 325i)? Second question relates to proper AC system psi and whether a low pressure switch is inactive if the system is too low? This indy says I can take a chance and throw a pound of expensive R12 in to see if it works but that it could be something else. The compressor does not come on when the AC button is pushed in.
Anyone know anything about this, please?
Jon

[JonE]

Thanks Bill, I'll check the site glass. It wasn't 80 degrees here in Minnesota, but I suppose even if the car was running and the compressor wasn't coming on the indy's guage still would read 50 psi? He also claimed that it is possible to over-fill the system. Does this make sense? How do you know when you're full? By the way, he wants $70/lb of R12. Is this reasonable? I thought it was at about $40/lb. Of course this could be his installed price.

[Bill R.]

the better a/c repair shops just last week picking up a condensor line and saw their prices for freon posted on the wall for customers.... And since pricing usually follows demand I would think Arizona is about as high as they come... And its not quite true that if the car is running the gauge won't read the same.... The freon is affected by the temperature of your condensor which will pick up heat from the radiator even with the fan running the condensor will probably pick up enough heat to raise the system pressure reading some... I would check system pressure cold , engine not running just to get an idea what it actually is... On an 80F day here I will get a static pressure of over 100psi on a charged system...If you have 50 then you typically will have to add one more 12 ounce can to get enough in for the system to run...When its running you slowly charge the system until the sight glass no longer has bubbles in it.... Its better to do this very gradually, add some let it run for awhile ,check sight glass and system pressures, add some more ,wait a few more minutes with it running..etc.. and the A/C blower should alway be on max , with it set to the coldest setting...






Thanks Bill, I'll check the site glass. It wasn't 80 degrees here in Minnesota, but I suppose even if the car was running and the compressor wasn't coming on the indy's guage still would read 50 psi? He also claimed that it is possible to over-fill the system. Does this make sense? How do you know when you're full? By the way, he wants $70/lb of R12. Is this reasonable? I thought it was at about $40/lb. Of course this could be his installed price.

[JonE]

Thanks for the info and the fill procedure, Bill. It sounds like the system is just too low right now to engage the compressor. I'll have to talk with the indy about his freon price. It'll start getting hotter here soon...