A/C blower weakens ---?
Thread Starter
Junior Member
Joined: Dec 2005
Posts: 54
Likes: 1
A/C blower weakens ---?
quick question.. maybe someone went through this experience before..
my w124 (92) a/c works really good. original. i noticed after driving 20 mins or more, the blower starts slowing down. no problem about the coldness. its the blower that wears down after a while. i can always switch to "auto" or high and it will blow stronger thus making it really cold.
is it the blower??
what do u think?
my w124 (92) a/c works really good. original. i noticed after driving 20 mins or more, the blower starts slowing down. no problem about the coldness. its the blower that wears down after a while. i can always switch to "auto" or high and it will blow stronger thus making it really cold.
is it the blower??
what do u think?
Super Member
Joined: Jul 2005
Posts: 717
Likes: 1
From: Manassas, VA, USA
2011 VW cc, 2004 ML350
quick question.. maybe someone went through this experience before..
my w124 (92) a/c works really good. original. i noticed after driving 20 mins or more, the blower starts slowing down. no problem about the coldness. its the blower that wears down after a while. i can always switch to "auto" or high and it will blow stronger thus making it really cold.
is it the blower??
what do u think?
my w124 (92) a/c works really good. original. i noticed after driving 20 mins or more, the blower starts slowing down. no problem about the coldness. its the blower that wears down after a while. i can always switch to "auto" or high and it will blow stronger thus making it really cold.
is it the blower??
what do u think?
MBWorld Fanatic!
Joined: Dec 2006
Posts: 1,042
Likes: 1
From: Bellevue, NE
1995 E320 SE, 162,000 Miles (Sold) 2007 CLK350 Cabriolet 2014 ML550
Paul is probably correct and you are just experiencing the normal modulation of the blower.
Also, be aware that the HVAC computer controls the blower speed by its current draw rather than voltage. The HVAC computer calculates the current draw setpoint based on temperature requirements and then gives more or less voltage to the motor until it sees the desired current draw. Kind of a strange way of controlling it, but it makes sense. It's possible that something causes the motor to increase friction as it warms up and then it draws the same current while turning more slowly. I would think this would be accompanied by a squeeking noise.
This info came from my interpretation the service manual, and the fact that I do HVAC controls for a living.
Also, be aware that the HVAC computer controls the blower speed by its current draw rather than voltage. The HVAC computer calculates the current draw setpoint based on temperature requirements and then gives more or less voltage to the motor until it sees the desired current draw. Kind of a strange way of controlling it, but it makes sense. It's possible that something causes the motor to increase friction as it warms up and then it draws the same current while turning more slowly. I would think this would be accompanied by a squeeking noise.
This info came from my interpretation the service manual, and the fact that I do HVAC controls for a living.
Senior Member
Joined: Apr 2007
Posts: 352
Likes: 91
Paul is probably correct and you are just experiencing the normal modulation of the blower.
Also, be aware that the HVAC computer controls the blower speed by its current draw rather than voltage. The HVAC computer calculates the current draw setpoint based on temperature requirements and then gives more or less voltage to the motor until it sees the desired current draw. Kind of a strange way of controlling it, but it makes sense. It's possible that something causes the motor to increase friction as it warms up and then it draws the same current while turning more slowly. I would think this would be accompanied by a squeeking noise.
This info came from my interpretation the service manual, and the fact that I do HVAC controls for a living.
Also, be aware that the HVAC computer controls the blower speed by its current draw rather than voltage. The HVAC computer calculates the current draw setpoint based on temperature requirements and then gives more or less voltage to the motor until it sees the desired current draw. Kind of a strange way of controlling it, but it makes sense. It's possible that something causes the motor to increase friction as it warms up and then it draws the same current while turning more slowly. I would think this would be accompanied by a squeeking noise.
This info came from my interpretation the service manual, and the fact that I do HVAC controls for a living.
Thread Starter
Junior Member
Joined: Dec 2005
Posts: 54
Likes: 1
thanks for the input guys.....
i set it on "auto" although the air stays on high blower i manually depress it since it gets really cold. i'll try setting the temp to 75 as advised... i'll let you know.. thks!
i set it on "auto" although the air stays on high blower i manually depress it since it gets really cold. i'll try setting the temp to 75 as advised... i'll let you know.. thks!
MBWorld Fanatic!
Joined: Dec 2003
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this is exactly what i do as well. auto, 75 all year. cool enough in heat and warm enough in cold. less wear on switches and so on. i generally keep it on the econ position and only use the AC when necessary.
