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Old 08-13-2012, 04:56 PM   #1
Registered User
Join Date: Oct 2002
Location: Seattle
Posts: 321
My Ride: 2001 325i
P0128 Code, AC not working. Need advice!

Hi all,
My 2001 325i (~95,000 miles) is throwing the P0128 code which I understand is typically a bad thermostat. I am initially thinking of replacing the thermostat and expansion tank and water pump as well as doing a full coolant flush. My belts are new and coolant is full. I don't want to have to replace hoses as they sound like the hard part, but maybe someone can convince me I need to.

Here's the problem though: I recently turned my AC on for the first time in probably months and it made a strange noise which has since gone away, but it doesn't blow any cool air whatsoever. Reading other threads, it sounds like the final stage resistor (which I've changed twice) and coolant temp sensor could also be possible culprits to the P0128 and AC issue. I'm wondering if the two issues are related...

Can anyone provide tips to help me root cause this? I have a code reader so can read sensor temps, etc, but don't know where to start. Replacing the thermostat looks easy, but getting my AC to work is very important so need to get this root-caused and resolved ASAP.

Last edited by Dre325; 08-13-2012 at 05:14 PM.
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