Why would this not be a good idea? HVAC plug

[Texas82GP]

Too many amps or a bad connection which adds too much resistance.

 

[Ribbedroof]

Too many amps or a bad connection which adds too much resistance.

My point exactly

It's a 12 ga wire, handles the load fine on cars that don't have that terrible connector in the middle of the circuit. It's the same gauge as the charge wire from the alternator, which seems to be fine...without a poorly designed connector in it.

IMO, adding a relay to a wire going to a relay makes no sense.

 

[fleming442]

Boy, that escalated quickly.

 

[64nailhead]

My point exactly

It's a 12 ga wire, handles the load fine on cars that don't have that terrible connector in the middle of the circuit. It's the same gauge as the charge wire from the alternator, which seems to be fine...without a poorly designed connector in it.

IMO, adding a relay to a wire going to a relay makes no sense.

I respectfully disagree, it makes perfect sense because of what Jared mentioned that you agreed with. The cause of the issue is what Jared identified or both of those. The relay powered on pin 30 from a fused source from the battery with a #10 wire and a #10 wire and female pin from relay pin 87 to replace the current #12 wire should resolve all of the issue along with confirming good grounds from the HVAC area to engine, frame, and battery.

Another solution is to confirm/repair grounds as I suggested previously and running a new #12 wire in the harness. But the new harness wire turns into a genuine PITA.

30+ year old wiring tends to become less effective as time goes by. Along with some corrosion and aftermarket parts that might draw more than the OEM all lead to these type of issues. Give our cars another 20-30 years and we'll be changing our headlight harnesses as well.

 

[Bonnewagon]

Doesn't the fan ground connect to a firewall screw or something? I would look there and maybe fabricate a heavy guage dedicated ground going to the engine block. I've never melted the resistor- they just rust up.

 

[fleming442]

Lest we not forget that the blower motor amperage draw goes up with age as the bushings get crud in them and create resistance.

 

[64nailhead]

Lest we not forget that the blower motor amperage draw goes up with age as the bushings get crud in them and create resistance.

I know my resistance goes up as my bushings get crudded up.

 

[pontiacgp]

I know my resistance goes up as my bushings get crudded up.

I can relate to that....