Some good food for thought about blower motors

[Ronnie]

The following is quoted from RockAuto's Newsletter. I thought it was something we should think about since the blower motor module routinely goes out on our Reattas and is expensive to replace new.

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"Good Idea to Replace the Two Parts Simultaneously

 

The heat and air conditioning systems in some late-model vehicles (i.e. Ford trucks) combine the Blower Motor and Blower Motor Control Module/Resistor into one part. Combining the parts probably saves money on the assembly line. Vehicle manufacturers may also have realized it is a good idea to replace the two parts simultaneously; especially if it appears the Blower Motor Control Module/Resistor is what failed.

 

Vehicles built in the 1900s used relatively simple blower motor resistors. Turning down the blower fan speed switch on the dash adjusted the variable resistor so that it converted more current into heat, less current passed on to the blower motor and the motor spun the fan at a slower speed. If a portion of the variable resistor burned out like a light bulb filament, then zero current or a fixed amount of current would reach the blower motor, and the fan speed would no longer be adjustable. The blower motor might always spin the fan at full blast. A failing blower motor resistor would typically not harm the blower motor and vice versa.

 

Modern Blower Motor Control Module/Resistors use electrical current much more efficiently. A smaller amount of current is converted to waste heat, and the Blower Motor Control Module/Resistor feeds the Blower Motor pulses of current that rapidly turn it on and off (duty cycle) to maintain the desired fan speed.

 

As the Blower Motor wears out, it may start to suck up spikes of current that exceed what the Blower Motor Control Module/Resistor was designed to deliver. Imagine a computerized relay designed to rapidly cycle a low-wattage light bulb now having to rapidly power a high-wattage table saw on and off. The Blower Motor Control Module/Resistor cannot handle this high or unpredictable current draw and fails.

 

Connecting a new Blower Motor Control Module/Resistor to a failing Blower Motor can quickly destroy the new Blower Motor Control Module/Resistor. If the Blower Motor Control Module/Resistor needs to be replaced, then the Blower Motor should be replaced too. See the blower/resistor parts for your specific vehicle under "Heat & Air Conditioning" in the RockAuto.com catalog.

 

Tom Taylor,
RockAuto.com"

[2seater]

I know precious little about how our blower speed control actually works. There may be some validity to the caution but I wonder how many follow on failures our group has experienced after just replacing the module? I have only replaced one module, and that was in the car that became the donor, so very little time was accumulated after replacement.

[Padgett]

It is called "upsell". Where the blower is off-low-med-high (standard AC) that is a switched resistance mode. No module. Reatae have ATC which does have a module in the blower duct common to many many GM cars with ATC. This fails often enough I keep a couple around but is an easy R&R particularly if you leave the third (back) screw out and just use the two at the ends that are visible. Blower rarely fails but have seen the fan come loose on the shaft and make a racket when starting.

 

Part of the reason I do not care for RA.

 

Must admit that the infomercials/articles I have been seem lately have seemed shifted both away from us folk and to a room temperature IQ, Think of it as Idiocracy in action.

Edited October 22, 2021 by Padgett