Warm A/C, Charge is Fine....Any Ideas?

[insite]

my AC recently has become totally ineffective. it seems to have occured gradually. i checked the refrigerant pressures and they are fine. likewise, the condensers appear fairly clean (i blew them out, bumper off, about a year ago). i checked the valve behind the center console that controls the heater core to make sure it wasn't allowing simultaneous heat / air; it wasn't.

the low pressure side of the system (at the cowl panel) seems very cold to the touch. if i put my hand on the fan housing in the passenger footwell, it also seems cool. the air from the vents, though, is just barely cool. it isn't hot, it's just not cold. i'm thinking i may have a blockage in the evaporator coil or something. where is it located? my factory service manual shows everything but the evaporator.

anyone have any other ideas on a potential cause here? it's been pretty hot lately and this is driving me nuts. i'm a penguin....

[wvicary]

You mentioned a valve behind the center console that you checked, what is this valve? I thought they used a blend door and not a water control valve. I've seen the foam backing on the blend door fail and cause heating/cooling issues in the climate control. A sign of this failing is little chunks of foam coming from the dash vents.

I assume that the compressor and both cooling fans are cutting in. What was the low and high side pressures when you checked?

[insite]

You mentioned a valve behind the center console that you checked, what is this valve? I thought they used a blend door and not a water control valve. I've seen the foam backing on the blend door fail and cause heating/cooling issues in the climate control. A sign of this failing is little chunks of foam coming from the dash vents.

I assume that the compressor and both cooling fans are cutting in. What was the low and high side pressures when you checked?

it may be a flap that i checked. when i changed the climatronic from Lo to 85F, there is a control cable that moves a valve / flap. if i look from the passenger's footwell up into the center of the dash behind the radio, etc, this is where the mix valve / flap i mentioned is located. as for the foam from the dash vents, i DEFINITELY have this issue. so you think maybe the blend door is not sealing and i'm mixing air from the heater core with air from the evaporator?

as for pressures, i used crappy guages, but they should do; low was just shy of 45psi and high was around 215psi when it was 93F outside. the compressor and both condenser fans are definitely cutting in. thanks.

[wvicary]

The pressures seem okay so I would think you have unwanted heater core air mixing with the evaporator air. Some folks have repaired these blend doors but I've only replaced them once.

[insite]

The pressures seem okay so I would think you have unwanted heater core air mixing with the evaporator air. Some folks have repaired these blend doors but I've only replaced them once.

are there two? one behind the radio and one above the passenger footwell?

[insite]

i found a schematic of the system, but there don't seem to be any part numbers for the mixing doors. are they shown on here?

[seafeye]

i found a schematic of the system, but there don't seem to be any part numbers for the mixing doors. are they shown on here?

A while back i found the following...Hope this can help in your problem... ;)

The AC Climatronic unit is actually manufactured by Audi. There is some sort of serial data stream (not CAN) that allows the AC unit to display engine parameters. This works on 1997-2000 boxsters.

To switch from F to C:

Hold down the recirculating button then push both the temperature + - buttons.

To access diagnostics:

Hold down the Recirculating & Air up buttons for 5 seconds. The + - buttons go up and down through the list of "c" codes. The center vent button switches the left display between the "c" code and its actual value. Press the Auto button to exit.

Here is a list of what can be seen:

0c - ERL

1c - Oil Temp?

2c - Inside temp. Sensor mounted in the aspirator assembly at the side of the dash.

3c - Outside temp. Sensor located inside the air inlet of the A/C unit.

4c - Outside temp. Sensor located in front grill of the radiator. The data is fed to the Climatronic from the instrument cluster. When not moving, the instrument cluster OBC temp display retains it's last setting until moving. This is to prevent heat emanating from the radiator affecting the temperature sensor. The A/C unit uses the lower of the two outside air temp values in determining fresh-air temp.

5c - Outside temp. (matches with OBC outside temp display)

6c - Coolant temp.

7c - Footwell discharge temp.

8c - Sun sensor (dash top)

9c - Sun sensor.

10c - Passenger compartment fan speed.

11c - Passenger compartment fan voltage.

12c - Temperature mix Flap command 1=COLD, 100=HOT

13c - Temperature mix Flap position

14c - Central Flap command

15c - Central Flap position

16c - Footwell/Defrost Flap command

17c - Footwell/Defrost Flap position

18c - Recirculation Valve command 1=OFF, 100=RECIRC

19c - Recirculation Valve position (feedback)

20c - Vehicle speed in kph, updating only once per second. (real speed, not speed+safety margin as in the speedometer)

21c - Engine RPM in hundreds. This too only updates once per second.

22c - ?

23c - ?

24c - Sun sensor, exterior lights switch & panel lights control (term. 58 & 58d voltage) - used for A/C panel display illum.

25c - ?

26c - ?

27c - ?

28c - Fan speed?

29c - ?

30c - Engine run time in seconds (255 max.)(=0xff)

31c - Timing counter

32c - Displays test

33c - Software version? Mine states 3.4

34c - ?

35c - Outside temp. from inlet sensor (filtered?)

36c - temp?

[insite]

i found a schematic of the system, but there don't seem to be any part numbers for the mixing doors. are they shown on here?

A while back i found the following...Hope this can help in your problem... ;)

The AC Climatronic unit is actually manufactured by Audi. There is some sort of serial data stream (not CAN) that allows the AC unit to display engine parameters. This works on 1997-2000 boxsters.

To switch from F to C:

Hold down the recirculating button then push both the temperature + - buttons.

To access diagnostics:

Hold down the Recirculating & Air up buttons for 5 seconds. The + - buttons go up and down through the list of "c" codes. The center vent button switches the left display between the "c" code and its actual value. Press the Auto button to exit.

Here is a list of what can be seen:

0c - ERL

1c - Oil Temp?

2c - Inside temp. Sensor mounted in the aspirator assembly at the side of the dash.

3c - Outside temp. Sensor located inside the air inlet of the A/C unit.

4c - Outside temp. Sensor located in front grill of the radiator. The data is fed to the Climatronic from the instrument cluster. When not moving, the instrument cluster OBC temp display retains it's last setting until moving. This is to prevent heat emanating from the radiator affecting the temperature sensor. The A/C unit uses the lower of the two outside air temp values in determining fresh-air temp.

5c - Outside temp. (matches with OBC outside temp display)

6c - Coolant temp.

7c - Footwell discharge temp.

8c - Sun sensor (dash top)

9c - Sun sensor.

10c - Passenger compartment fan speed.

11c - Passenger compartment fan voltage.

12c - Temperature mix Flap command 1=COLD, 100=HOT

13c - Temperature mix Flap position

14c - Central Flap command

15c - Central Flap position

16c - Footwell/Defrost Flap command

17c - Footwell/Defrost Flap position

18c - Recirculation Valve command 1=OFF, 100=RECIRC

19c - Recirculation Valve position (feedback)

20c - Vehicle speed in kph, updating only once per second. (real speed, not speed+safety margin as in the speedometer)

21c - Engine RPM in hundreds. This too only updates once per second.

22c - ?

23c - ?

24c - Sun sensor, exterior lights switch & panel lights control (term. 58 & 58d voltage) - used for A/C panel display illum.

25c - ?

26c - ?

27c - ?

28c - Fan speed?

29c - ?

30c - Engine run time in seconds (255 max.)(=0xff)

31c - Timing counter

32c - Displays test

33c - Software version? Mine states 3.4

34c - ?

35c - Outside temp. from inlet sensor (filtered?)

36c - temp?

helpful! i'll give it a run; thanks.