Yes that is a "viable" solution.

First - those water valves can cause the problem you mention if they are not closing properly.
When the AC is on then all the incoming air is chilled to the max (compressor runs most of the time and automatically adjusts is internal displacement to work with different heat loads)

Then the system reheats the air to the required amount to get the cabin to the temperature settings that you have selected. It pulses the water valves to keep the heater at the proper temperature to achieve this.

BUT - the system is also influenced by the outside temperature - as measured by, and displayed in the instrument cluster.
That temperature is digitally sent to the climate control panel and used by various programs to do the following
- adjust the heating and cooling programs to deal with extremes of outdoor temperatures.
- turns on the outside mirror heating (in 4 stages)
- turns on the washer nozzle heaters
- adjusts the timing for the rear window defroster when you turn it on.

If your outdoor temp sensor was missing, and the reading was always -40 then the car was doing everything it could to address sever cold weather - including upping the factors that control the heating. Actually it would not even operate the AC compressor under those conditions.

You also would not have access to the park vent function and the freezing road alarm would not be working.

Hope that helps - it is important to keep all the systems functioning on these cars - they are interelated.

Cheers
Jim Cash

• A/C question 99' 540i - ryan32591 2008-08-19 20:27:24 (132 views)
  • Re: A/C question 99' 540i - cal45fan 2008-09-24 00:54:31 (32 views)
  • Re: A/C question 99' 540i - ryan32591 2008-09-15 21:05:33 (60 views)
    • Re: A/C question 99' 540i - jimcash 2008-09-16 10:19:24 (63 views)
  • It sounds like the compressor has enough refrigerant to - JoeC 98 740il & 750il 2008-08-28 20:02:54 (65 views)
  • Re: A/C question 99' 540i - ryan32591 2008-08-28 19:27:06 (68 views)
  • Re: A/C question 99' 540i - jimcash 2008-08-20 14:50:26 (95 views)
  • Re: A/C question 99' 540i - rick540 2008-08-20 12:06:41 (70 views)