Fuse #2 Frustration (Class III Boomer)

[jinman]

FYI, a DC solenoid does not pull more current if it sticks open and does not "buzz". An AC solenoid does pull more current when open and if mechanically jamed open will burn up or blow a fuse. Some DC solenoids have a switch in them that opens when the solenoid engages and puts a resistor in series with it. These do pull more power when open, but they are very rare. I have never seen one.
Good job of trouble shooting.

Thanks for the info, Bob. I agree with your description of the DC solenoid. In my case, I think the solenoid had partially shorted windings and that was the cause of the increased current. Then the increased current caused a hotspot that lead to the deterioration and final failure of the insulation. At that point, it was a catastrophic internal failure. Had it been open, I'm sure I would have seen some pretty spectacular arcing and sparking.

Also, I did increase the fuse to twice the recommended value, but I would recommend this only with some caution. I would surely never go above that amount, and what really showed me the problem was when I jumpered the solenoid directly to the battery and it smoked. This is a technique I would recommend only to an experienced person who knows to wear goggles or shield himself from the possibility of an exploding solenoid. In retrospect, I should have been a little more safety conscious, but I got lucky.