AC Question (on converted system)

[ebod]

I have an 89 325i Convertible on which the AC was converted from R-12 to R-134 (I think that's the newer stuff). They did not change the condensers as part of the conversion. I recently re-charged the system. It now blow really, really cold for about 10-15 minutes. Then, it merely blows cool for a while. Does this sound like something is freezing up or something? Any thoughts about what this might be and/or how to fix it would be greatly appreciated.

[somecarguy]

Is the coldness dependent on speed? Does the front condenser fan come on when the ac button is pressed?


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[ebod]

Coldness is not dependent on speed--just amount of time that the AC has been on.

When I push the button, my car idles higher and you can feel a difference. I don't know if that's the condenser fan. I always thought it was because the engine was working harder to poser the compressor.

Thanks.

[somecarguy]

I think you should familiarize yourself visually with the condenser and the compressor fan. I’m sure you know that the pulley on the condenser spins constantly and the clutch is the outermost (aka forwardmost) part which will be stationary with the AC off but rotate with the pulley when the AC is on. verify that the compressor is running when the button is on - both when you first start the car and after it has stopped cooling satisfactorily.

With the car off look at the very front through the area below the license plate and feel for the large plastic fan. An easy way to tell if it is working is to turn the ignition to on but do not start the car and then press the AC button on - you should both hear the compressor clutch click and clearly hear/see the fan running.

[aaverhulst]

It may be that the refrigerant charge is slightly low and the evaporator is icing up. Might want to recheck your charge. What is your vent temperature when it's cold?

[Jeffnhiscars]

The ecu kicks up the idle speed when the AC is on and a faster moving vehicles will have better heat disappation via the condenser not to mention a compressor turning faster and more efficiently. This is also why jumping the resistor helps low speed AC performance...ie more air flow.