1999 - 2007 chevrolet truck and suv blower motor resistor

So your blower motor only works on high now? any lower speed you feel nothing , youve checked fuses? well then it is a good assumption your blower motor resistor is the culprit. there are a few ways to check and see if this is your issue . so lets talk about it!

first of all the blower motor resistor slows down voltage or current to the 12-14volt blower motor thats why high setting has no resistance so it wants full voltage and amps. to get a lower setting of speed the resistor forces voltage lower by turning  excess of the demand into heat. this is why they dont last forever but are usually cooled down by the air stream in the hvac assembly. So if your blower motor works on high only or you have some lower speeds that dont work its safe to assume that the resistor is the issue.
to test this you can use a DVOM(digital variable ohm multi-meter) to measure the volts DC to see if your getting voltage at all settings from the power connector that connects to the blower directly. one is a positive connection the other the negative connection as long as you dont put your leads for the meter in the same one your good , if the polarity is reversed you will see -12v if you flip it you should see 12 volts or +12v , start with the highest setting to see if power is there. this will confirm you have a direct power source from the switch (with ignition on of course) then go to your lowest setting your values on a good resistor will range from 1v-12v as you go through the settings if you have variable voltage readings on the resistor that slowly rise with the selector its operating properly.
If no its time to replace the resistor because it has failed. on the chevrolet trucks and full size suvs its a very simple process. if you would like a video demonstration on this your in luck Joe The Auto Guy has uploaded on on this issue and its very easy to follow directions so here is the video
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