The Electronic Climate Control/AC switch has been flashing, indicating a system fault. The blower motor does not operate when this happens. The problem is intermittent, and more common in damp or rainy weather. If I restart the car after a few minutes of running, the fault may clear and the system (both AC and heat) work perfectly.

Going through the diagnostic procedure, I consistently get the fault code 151: Alternator (D+ signal fault), and no other fault codes.

Any suggestions on what to do next? What are the likely causes of the code, given the above symptoms?

 

That is the D+ terminal of the alternator that it references in code 151. My suggestion is to chase some wiring with the battery removed and see if anything is shorted, broken or otherwise.

It seems that you are loosing power to the blower.

 

The fault seems to be in remission now, which prevents diagnosis. If I understand correctly, the fault would have to be occurring before it could be detected by checking the wiring. The blower operates normally when the fault code is not displayed. If it's a "hot" wire that's interrupted, then is it most likely to be between the blower control and the motor? If farther up the source line (closer to the battery), wouldn't other systems also be affected? Would the D+ fault also appear if the ground were interrupted?