Totally Baffled - HVAC

Several years ago, the 'spindle' on my blower control switch on my 2001 E150 XLT Club Wagon got so damn hot it nearly melted the knob....and its harness. I replaced the blower control switch last year. Same problem resurfaced. I have now replaced the blower fan, the control switch and its harness....and the damn spindle gets extremely hot after about 15-20 minutes? The only component I have not changed is the blower relay. I have to continually check how hot the spindle is and, if hot, turn off the fan. Other than this, everything works fine - all blower speeds, vents, A/C.


I am at a loss!!! No where on the Internet can I find similar experiences.


Please help!

Getting hot at a switch is a sure sign of a poor connection. Where there is not enough metal to metal contact to transfer the necessary amp load without creating the "fuse effect" . So, after the first bad switch, did you change out the terminal connectors, or the crimped on leads, to be sure they are not burnt, corroded or bad in general? If the lead wires are bad at the connectors, no amount of new components will fix this. When there are bad connections, amp load will tend to heat up at the bad connection and transfer that to the switch itself, and melt anything near it- Just like a fuse blows when it is overloaded. You don't have a short, just a really bad connector, or connection. May be a simple as putting new ends on your wiring harness, or replacing the wiring harness altogether.

I have seen this many times on Astro van fan blower motor connections at the realy module. Napa sold the wiring harnesses separately because of this inherent issue.

As said solid connections are important. When a connection doesn't make proper contact it is trying to jump the gap so to speak and that is where the heat comes from that melts things.

Getting hot at a switch is a sure sign of a poor connection. Where there is not enough metal to metal contact to transfer the necessary amp load without creating the "fuse effect" . So, after the first bad switch, did you change out the terminal connectors, or the crimped on leads, to be sure they are not burnt, corroded or bad in general? If the lead wires are bad at the connectors, no amount of new components will fix this. When there are bad connections, amp load will tend to heat up at the bad connection and transfer that to the switch itself, and melt anything near it- Just like a fuse blows when it is overloaded. You don't have a short, just a really bad connector, or connection. May be a simple as putting new ends on your wiring harness, or replacing the wiring harness altogether.

I have seen this many times on Astro van fan blower motor connections at the realy module. Napa sold the wiring harnesses separately because of this inherent issue.
As I said, the blower, resister, switch were fairly new....and I just today replaced the resistor harness ( i.e. connector ) and the switch harness. The resistor harness connectors looked corroded and the switch harness was somewhat melted. Applied dielectro grease to all connectors. So, now I remain at the beginning! Everything works but the damn control switch spindle heats up slowly until its pretty hot....and I can feel all four of the harness wires behind the switch are 'warm'. The only item that has not been replaced is the blower fan relay.

As said solid connections are important. When a connection doesn't make proper contact it is trying to jump the gap so to speak and that is where the heat comes from that melts things.
As I said, the blower, resister, switch were fairly new....and I just today replaced the resistor harness ( i.e. connector ) and the switch harness. The resistor harness connectors looked corroded and the switch harness was somewhat melted. Applied dielectro grease to all connectors. So, now I remain at the beginning! Everything works but the damn control switch spindle heats up slowly until its pretty hot....and I can feel all four of the harness wires behind the switch are 'warm'. The only item that has not been replaced is the blower fan relay.

Replacing components won't fix it if the problem is in the harness or the connectors....