Vehicles

saab - replacing ac blower fan motor controller transistor

From the time I bought the saab the air conditioning fan was only slightly controllable, it was either full blast or very low. Even on low it was never off, actually it was impossible to turn it off. Even with the the entire ACC system turned off the fan was still on low. Anyways about a week ago the fan speed chaning all together, it was stuck on the highest setting. I was still able to adjust the temperature, however nothing I did would change the fan speed. I even tried disconnecting the ACC (automatic climate control) panel and it still stayed on. The saab scene forums indicated that the blower motor control was probably shot. This is a $200 part, ouch. Some members had reported success just replacing the transistor inside the blower motor control. $20, 1 week of shipping, and 2 hours of labor later, the blower is back up and running. I always thought the saab only had 3 blower levels based on the LEDs on the ACC panel. As it turns out, you press teh up button to turn the fan higher and lower to turn the fan lower. There are actually about 10 fan levels. I had always thought it was just high and low. The fan speed is something that had bothered me for the last 1.5 years since I had the car and, now that its fixed, I am glad the saab forced me to do something about it.

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remove the false firewall, shown just behind the engine
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the blower motor control has the yellow label on it
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gigantic heat sink
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replacement transistor from toshiba, 2SD1525
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$10 + shipping
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stick screwdriver through top hole to remove screw holding board (transistor) to heat sink
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board removed
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transistor desoldered
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i used artic silver thermal compound on the new transistor, they used silicon based paste at factory
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ready to reinstall

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