I posted a while ago about how my heater motor won't blow on high. I replaced the relay and I'm having the same problem. The fan has 1-2-3-4 settings and it will blow on 1 and 3 but if it's on 2 or 4 it doesn't blow at all. One of the prongs in the relay was burned up a little so I traced the corresponding wire going back to the fire wall and I don't see any other problems. Any suggestions?

 

Follow the big red wire a little further.

You'll come to a connector of the stupidest design EVER; the plastic of the connector body is all that holds tension on the contact. Stupid. It's about right above the pass side valve cover. Attempt to unplug it, and in case you can even get it apart (the plastic often melts into one charred lump), yyou will find that it's burnt to ashes. Did I mention, it's a STOOPID design?

Replace it with a pair of the BIG HEAVY-DUTY yellow slide terminals. Insulated, if possible. Not the little baby weenie ones that are just like the red ones and the blue ones, except yellow; get the big thick heavy-duty ones.