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BMW E28 E24 E23 Air Conditioning – Can It Be Improved?

May 20, 2010

This answer is applicable for many BMWs in addition to the one listed below.

Q
car year: 1988
car model: 535is
I live in Houston Texas where the summers are very hot and humid. I would like to significantly improve the cooling capacity of my A/C. While the air is cool at the vents, the blower simply doesn’t blow strong enough to effectively cool the cabin. Is there anything that can be done to increase the blower speed and/or the force of the air from the vents?

A
We’re familiar with the weak A/C capacity on the E28 chassis (5 series 82-88).  This would also apply to other early model BMWs, up through the early 1990s.  Even here in the north, these A/C systems are barely adequate on a sunny, 80 degree, day.  There simply isn’t enough air duct and outlet vent capacity to keep the interior cool overall. When the ambient temperatures are high, and the sun is full, the front seat riders are typically OK if the vents are directed at the body, but the rear seats will never really get cool.

If the system is working at peak efficiency (clean condenser and evaporator, properly functioning expansion valve and proper system pressure and charge volume), there isn’t much else you can do. I don’t know that more blower speed would really help, as the duct-work can only flow so much air. And, the only way to increase the blower speed would be to run it at more than the 12 to 14 volts that the system is normally running or to replace the motor with a custom unit that is built to run at a higher RPM.

It’s interesting to note that the similar vintage E24 chassis (6 series through 89) was available with optional rear seat A/C, which has its own complete evaporator,blower and ducting.

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