Need help with diagnosis

[jshepard]

I bought a 1995 318 about a year ago that I have been rebuilding as I have had $$ to do so. I love the car, although I wish it was a 6 cyl. My latest project, given that it has been so damn hot in southern CA, is the A/C. My A/C has never worked. I don't know if the problem is the compressor, A/C clutch, or maybe somethng else, so any info as to how to diagnose would be great. Here is what i know:

1) The blower works
2) A light comes on within the AC button when I push it in
3) There is no cold air that comes out at all
4) I don't feel the tug on the engine that I do when I turn on the air of other cars where the AC worked.
5) It uses the new freon (r134?)I don't remember the name

Question: How could you tell the difference betweent whether the compressor or the clutch is the problem?

Is there a relay or other switch that could be the cause of the problem?

Thanks for any help,

jeff

 

[wood_e]

Is the system holding any refrigerant? You can usually tell when the compressor engages, however sometimes when compressors and clutches fail the pulley siezes... not good. I would check first if you have any refrigerant in the system at all.

My guess is that it probably needs a recharge of R134

 

[jshepard]

That's a good point. I forgot to add to my initial post that I was told that the problem is not a lack of R134. Thanks thought, that was an excellant point.

Jeff

 

[Kirby]

IFit is not a lack of refrigerant, then it may be the pressure sensor or associated wiring. In most cars, I assume BMW also, there is a pressure sensor that enables the compressor clutch. If the pressure is to low, the clutch will not energize to prevent damage. It seems to me the first check, assuming you do have refrigerant, is to check for voltage at the clutch. If you have voltage but it is not engaged, you have a bad clutch. If there is no voltage check the pressure with a gauge. If you have pressure, then the sensor is suspect. If you replace the sensor, you will lose your charge.

 

[jshepard]

Excellent, excellent suggestions. Thanks. I will check these things out. If you think of any other suggestions let me know. Jeff