Chrysler Repair: Plymouth Breeze heater fan resistor, resistors in series, amp fuse

Question
Hi,
I've seen your answer about this subject. I'm helping a friend repair this same issue. I've replaced the resistor block twice, the last time it failed within a month. As an electrical engineer, I was irritated by the short life of this resistor block. I have diagnosed the failure to an open diode mounted in series with one of the metal wirewound resistors, same failure in both other units. I plan to replace the diode with one of higher current rating. My question to you is do you have any electrical drawings showing the internal connections of the block as it relates to the fan wiring? I dont have access to the service manual. If this fix works I can post a part number and procedure to help others pay $60 or more to a dealer for replacement. (That is for those who can work a crimp connection or soldering iron!)

Answer
Hi Ron,
I'm glad to have your interest and expertise. The Haynes wiring diagram shows that current from the battery (when the ignition in the "run" position) is fed thru 30 amp fuse #1 in the junction box under the dash and then on a dark green wire to the blower motor. The current is then carried from the blower motor over one of 4 pathways (depending upon the position of the blower switch in the dash) to ground. On high speed the current is shunted on the black/tan wire directly to ground. On each the other three wires the current first passes thru a "black box" called a thermal limiter (what you have identified as a diode) and thence to a 3 resistors in series voltage divider with taps after one resistor (light blue wire (medium high speed)) or 2 resistors (light green wire (medium low speed)) or all three resistors (tan wire (low speed)). I am pleased to learn that you have identified the cause as the failure of the "thermal limiter" but cannot help in identifying exactly what it is or a part number. It must be a current limiting device but what its characteristics are is unknown other than it must cut out at somewhat less than 30 amps.
So please let me know if you come up with an over-the-counter replacement that could be acquired at an electronics supply house and I will be sure to post your answer and bring it to the attention of future questioners.
Roland