HVAC fan Issue

[Bells Yorker]

My 68 New Yorkers fan will blow the fuse when set to the highest speed, it will run all day at low and medium. I am assuming it is the resistor but i have read on here that when the resistor is bad the fan will ONLY run on high, so that is confusing. I have checked the wiring connectors and used contact cleaner on them.

Can I access the resistor through the glovebox or do i have to take out the dash?

Could the fan switch be the problem?

Thank you in advance.

 

[thrashingcows]

I would say it's an old blower motor, and 47 year old wiring, and old switches putting too much draw on things. Converting to a relay system for the "high" setting on the blower motor would solve this issue. You would then have power going directly from the battery, to the blower motor, and the original switch would just be used as a trigger.

I'm into 1st Gen cummins trucks (89-93) and this is a common...and somewhat necessary upgrade for our blower motors, as well as headlights.

 

[commando1]

I am under the assumption when HI is selected, the resistor is bypassed altogether and the blower is getting the full 12V.

 

[Yatzee]

Could be back-feeding through the resistors causing an unusually heavy load. I'd check the draw on the blower motor with direct 12v then with each leg of the resistor wires. If you don't own a clamp style amp gauge, and your wife's having a secret affair with an electrician, borrow his.