Overheating Blower Connection at Fuse Panel

[Classics Fan]

I recently posted about a problem I was having with the cigarette lighter in my 1971 Jimmy Custom with AC. Related to that post and subsequent thread I discussed how I found the HVAC blower connection at the fuse panel melted. (I had begun smelling something hot just previous to this when the blower was run on high). I chalked that up to a bad/corroded/oxidized connection and replaced the melted female spade connector and short length of wire that showed signs of melting, and added a 20A inline fuse at the panel connection.

Fast forward to yesterday, the first time I’d driven the vehicle after the work described above. Within 10 minutes or so of the blower being run on high speed I caught a faint whiff of hot electrical but it seemed to go away. However when I returned home and looked I found the new fuse panel connector had a dark spot on it and it cracked when I pulled it off the fuse spade. It only gets hot with full voltage to the blower on high, not on lower resisted voltage at lower speeds. Also, the 20A fuse did not blow. I’m confident the connection to the fuse panel was tight.

So my question to the folks who understand electrical much better than me, what can cause this? I assume high resistance in that circuit? Blower motor? Or something else?

[dagnabbitt]

I am not an expert, but if the failure point is where you describe it might be due to increased resistance: likely by poorly crimped connectors, or a poor connection with the fusebox terminal.

[D.B]

I had a melting connector issue with mine and found out it was a bad ground strap on my blower motor. I made sure it was connected to a good ground spot and it fixed my problem.

[Classics Fan]

Originally Posted by dagnabbitt

I am not an expert, but if the failure point is where you describe it might be due to increased resistance: likely by poorly crimped connectors, or a poor connection with the fusebox terminal.

I’ve double checked the crimp and connection. Both are good and tight.

[Classics Fan]

Originally Posted by D.B

I had a melting connector issue with mine and found out it was a bad ground strap on my blower motor. I made sure it was connected to a good ground spot and it fixed my problem.


Attachment 2413844

I was optimistically hopeful your suggestion would be the solution. I disconnected the blower ground on the firewall/cowl, wire brushed the attachment screw, washer and ground wire eyelet and reattached it. Unfortunately the short length of wire (approximately 2”) between the fuse panel and the inline fuse I installed still gets hot within a few minutes of the blower running on high speed. The wire getting hot is the same gauge as the orange factory wire it’s connected to that runs to the blower.

[dmjlambert]

Check to make sure nothing is dragging on the blower squirrel cage, such as an obstruction or rats nest. That will make the motor draw more current.
Make sure the connector on the fuse panel is good and clean and doesn't have rust buildup, that will cause resistance and heat. There's only 2 screws holding the fuse panel on, remove them and flip the fuse holder over and inspect the back for rusty connections and melted plastic there.
Make sure you have a 16 gauge 6 to 9 inch length of fusible link wire connecting the main 12 gauge red wire at the junction block near the battery. That is what helps protect the unfused 12 gauge wiring in the truck.