Plymouth Repair: Air Diverter, plymouth reliant, 2l

Question
1985 Plymouth Reliant 2.2L Carb
The air diverter completely melted down.  When I checked the odor of burning plastic I found that one of the hoses had come off of the diverter and the plastic housing had completely fried.

I'm going to replace the diverter and see what happens.  My question is what causes the diverter to melt?  I don't want to replace it and have it happen again.  Thanks.  

Answer
hello melissa
this is a short . i would replace it but let it run for a good long time and see what happens and also check wires around it to make sure that they are ok. good luck to u hun and if u need more help u let me know u have a pretty name pete