Blower motor not working

[01saharatj]

There is a 2001 service manual in the resources section that shows all of this, but it's hard to navigate because it's not hyperlinked. The 2000 manual is mostly if not exactly the same as for the 2001 and it is hyperlinked and much easier to navigate.

plus there are so many adds on here they make it even more difficult to navigate when searching for something … very frustrating while searching for info while in the middle of troubleshooting…

 

[01saharatj]

Never mind I found it

 

[01saharatj]

Never mind I found it

 

[01saharatj]

Update: replaced motor and resistor. At the moment and it’s working (all positions) so ****FYI old blower would still function with full 12 volts directly from battery but hook up to circuit, no good*****. I did add the relay as suggested from another poster and was able to get it to work. Only concern now is the internal divert to vents. Seems vacuumed not functioning but will dig in more tonight.

Thanks to all that helped.

 

[FarFire70]

I totally understand that a motor draws more current when the load increases, that is a given on any inductive load. But we have fixed resistors on 3 of the speeds to control the speed, so on the 3 lower speeds the circuit is resistive-inductive. The resistor drops the voltage which in turn limits the current. This is proportional to the amount of resistance, so the more resistance, the more current gets limited. (We know that current is limited through the resistor because if it wasn't, the motor would simply draw enough current to maintain it's rated speed and the resistor would not slow it down). So I don't see how the lowest setting, with the most resistance, would proportionally draw more current than any other speed that is controlled by a resistor. One could argue that the high speed circuit, being basically all inductive, would be more likely to experience runaway current when overloaded as there is no fixed resistor in place to limit it.

The other issue I have a problem with is why aren't we seeing low speed meltdowns? Granted I have only seen 6 meltdowns but they have all been the high speed. 3 were Ford vans in a fleet where the high speed terminal on all 3 dash switches melted, 1 was on my 1987 Mercedes 300 where the high speed fuse melted repeatedly, 1 was my Jeep where the input terminal to the mode switch (where all the negative current passes) melted when the blower was on high. The 6th one is the one in this thread, which was the high speed terminal on the blower switch.

I'm not discounting your theory and this is an interesting discussion which I plan to research more. Do you have any examples of low speed meltdowns, or any references to your theory?

Personal experience. Replaced blower motor resistor twice over the life of the Jeep (150k miles) - both times were after the lowest setting stopped working. Resistor showed burnt damage.

I'd rather the resistor is the fuse vs the switch. But, when it isn't, the switches melts - and examples have been on lowest setting most typically (but this is more anecdotal vs my own experiences).

Personal experience number two or three...

Just pulled this today from my Jeep.

New motor going in along with a fresh resistor pack.

Share for awareness.

The current to break down those solder joints would have gone through the HVAC switch without the relays I installed.