Q: How do I know if it's my blower motor resistor or the resistor switch that's not working?

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My A/C and my heat won't turn work and nothing blows out and it doesn't seem to defrost really well when it's cold. I'll turn the switch and the green light says its on but nothing seems to happen. I took it to auto zone they said my blower motor is fine and could be either the resistor or switch, but how do I tell which one I need?

My car has 100100 miles.
My car's transmission is unknown to me.

The referenced parts are tested with an ohmmeter. The resistor block must have a specified resistance across each element on the block. However, if any resistors are open (infinite resistance), the block is just condemned and replaced automatically. Occasionally, you might be able to see that the resistor block is obviously broken (elements are open). Switches are tested using an ohmmeter or continuity tester. There are other electrical components, and wiring, in the system that can cause it not to work. If you desire that this problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a blower motor diagnostic and the responding mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.

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