I have a '96 850 Turbo Wagon. Recently I had the a/c evaporator replaced at the dealer.

Now that the weather is a little warmer up in Canada (23 to 27 degrees C) I have had problems with the system freezing up. It seems that during highway driving and low fan speed, the evaporator seems to ice up after about 30 minutes. I believe it is icing up as the air flow becomes significantly reduced (even if the fan is then set manually to full speed) and the air is cool rather than cold. If I turn off the air conditioning, in a few minutes the air flow returns. I have also noticed that I often have a thin layer of ice forming on the line at the firewall between the evaporator and the accumulator. Icing also sometimes occurs at the firewall on the line from the condensor to the evaporator. The a/c clutch on the compressor does cycle on and off when the evaporator is not iced up. The last time the evaporator iced up and air flow was reduced, I believe the compressor was staying on full time (I didn't think to check the compressor the other times the air flow reduced).

Icing should not be a normal situation. Does anyone have suggestions on what might be the root cause (e.g., over or under charging of the system, a faulty low pressure switch,...) ?

Thanks in advance,

Garth Gullekson

1996 Volvo 850 Turbo Wagon
2001 Subaru Outback
1978 Porsche 911 (no A/C !)

Check for a dirty filter if you have one or your system might be overcharge!

As part of the evaporator replacement, the dealer puts in a new pollen filter, so I don't think filtering is the issue.

- Garth -

Just had a similar evaporator freezing condition on my vehicle, and it was supposedly resolved by Volvo under warrnaty with a SW - ECC Upgrade with Vadis 6.0 whereby the software upgrade modifies the control of the evaporator temperature to prevent if from freezing due to reduced airflow and cooling under high temperatures and humidity conditions. Tech No. 87-31

Jone,

I assume the fix you refer to was for the S40/V40, and not directly applicable to my old 850?

- Garth -