How come my A/C won't blow very cold when it is over 90 degrees or in stop and go traffic?

The condensor is clean, the radiator is clean. The evaporator has been replaced, the condensor replaced, it has a variable orifice valve, the receiver drier has been replaced. It has R134 and the compressor does not cycle on and off as if it were low. What is going on?

THanks.

If the air is not blowing cold either at idle or at speed, then it is not likely that the problem is air flow, although it will make a difference in cabin temperature sitting at a stop in hot weather. The compressor won't always cycle if the charge is slightly low. There will be a buildup of ice on the return side, and more water drained after the car is parked for a bit. One of my cars (a 760) had a similar problem, topping off the charge with a can of 134r from Wal-Mart fixed it.

Regards,
--
Will Dallas, www.willdallas.us, www.willdallas.org, www.willdallas.com 86 245 DL 205K miles, 93 940 250K miles, 88 765 GLE 149K miles, 86 244 DL 200K Miles, 88 744T 200K miles

Thanks. I thought the same thing the other day. I added half a can of freon. It seemed to help a little. Then the other day that it was hot out (90 deg.) I was going down the highway and the pop off valve on the compressor blew out a couple of times. The high pressure switch also shut down the compressor a couple of times. (Too much pressure!) So I let some more freon out of the system. I will see if it helped any on the way home today.

One other thing to check..
Feel the hoses going to the heater core.. Are they both hot?

Even if the AC is fine you could be heating the same air you are trying to cool.

I grabbed the two hoses going through the fire wall and they were both hot. I thought that water was supposed to always circulate through the heater core? I did find a hole in the vacuum line going into that valve where one of those hoses plug into. I thought I fixed it with a short piece of straw and electrical tape. Is that valve the heater valve? Does that open and close to let in coolant? Where does the other end of that vacuum line plug into after it goes through the firewall? Do you know if that line can be purchased? Does this have anything to do with my dash vents switching to the defrost and floor vents while under load?

Thanks for your help.

Dear D.J.

Good p.m. and may this find you well. Hot water is only supposed to go through the heater core, when you want heat in the passenger cabin.

The heater valve, actuated by hose-supplier vacuum, opens and closes, in response to settings on the Climate Control Unit (CCU). A number of vacuum lines go to the CCU. Those lines go to vacuum "motors", which are rubber bellows. When the air is sucked out, that opens and closes the plastic "doors" in the air handling system.

Vacuum line can be bought from the dealer, or from an auto supply place. Be sure you get the right diameter.

The vacuum leak, which you likely have only partly patched, indeed could account for air flow changes, that you have not "ordered", by moving the selector knob, in the center of the CCU's front panel.

Hope this helps.

Yours faithfully,

spook