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The HVAC air in my civic will randomly stop working. When it stops working I run the self diagnostic and get the code 12. I've replaced the blower relay, but the system is still intermittent. When the system is working, no code is given through the self diagnostic. I've also check the blower resistor, but it is perfectly fine. The OMH's are the same as a brand new one. Any other ideas of what I could check? When the system is working, the blower works at every speed and both AC and heat work. When the system decides to stop working, no heat, no ac, no air and code 12.

 
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Sounds like your control unit might be crapping out. This is the module right below your radio.

 
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When fan is not turning, with key at II and fan switch on high. Apply pressure/twisting to the connector and wiring going to blower fan and see if it tries to work, then try the same thing at the transistors connector.

 
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Then smack the bottom of the fan motor and see if it starts running.

 
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That's what I was afraid of. I'll have to tear into it sometime.

 
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Thanks, I'll give this a try before I look into the control module.