GoodMatt

I've searched for an hour or so, but can't seem to find anything that helps greatly. I've got an '00 S4. Last summer the A/C was weak, but acceptable. The few hot days we have had this summer, it's not cutting it.

Today it's upper 70's. Not smoking hot, but warm enough that my black interior needs some help to cool down.

The air coming out is probably warmer than outside temp. I don't believe the compressor is kicking on.

On-board diag numbers:

2) Digital value of int temp sensor (headliner) = 128
3) int temp sensor in instrument panel = 114
4) intake duct temp = 69
5) outside air ambient temp, front = 54
6) outside air temp = 146 (yes, 146)
7) ambient temp at blower = 157
20) a/c clutch volts = 13.7 (recirc on or off)
29) a/c compressor speed = 57 (constant, regardless of rpm)

Any ideas?

Thanks,
Matt

JasonS4+Festicle

only hot air would come out of the vents - even with the temp turned all the way down.

It turns out, I had a bad outside air temp sensor.

What happened in my case was that the car thought it was really cold outside and would not allow the A/C compressor to kick on.

There are 2 ambient air temp sensors. One is just in front of the radiator (attached to a little black plastic thing) - it comes off of the power steering cooler loop.

The other sensor is located under the pollen filter. It's a PITA to get to because it snaps in from the back and cannot be accessed even if you remove the pollen filter. I went from underneath the passenger side kick panel and just reached up and did it that way.

If you scan with VAG-COM under 'climate control', you should find a code which may indicate which sensor (if it's the sensor) is bad.