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Air conditioning weirdness[740-760/1991] posted by Mike on
Saturday, 30 May 1998, at 2:20 p.m.
The air conditioning on my 1991 740 turbo wagon does something unusual. When the AC is operating and the upper panel ducts are selected, cold air blows from the left and right ducts. However, the central duct blows warmer air--a very noticeable (and annoying) temperature difference, though I haven't taken measurements. Is this common? Any advice would be appreciated.
Re: Air conditioning weirdness[740-760/1991] posted by abe crombie on
Saturday, 30 May 1998, at 3:48 p.m.
Your refrigerant level is getting low and the evaporator is not cold all the way across from one side to the other. The way the air blows out of the evaporator case into the air distribution housing does not mix it well and you get this temp differential. Another possibility is a defective evaporator. Some evaporators have parallel flow (your car is one of these) where the refrigerant goes into the evaporator goes across half of the core and then goes through the end tank of evap. and turns 180 degrees and goes back across the other half. If the divider that separates the end tank that has the entry and exit fittings gets broken from the pressure pulsations then the refrigerant doesn't go across and back and only one end of the evap. gets cold.
The only way you will know is to get a competent a/c shop to eavacuate your sytem and see haow much refrigerant is in there. If it is low then fix leak and your a/c is repaired. If it isn't low then replace the evaporator.