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I have an '03 F250 and the second position of the blower switch doesn't work. The first, third, and fourth are all fine.
I bought a Motorcraft YH-1670 blower switch, but can't figure out where it's located?
I looked behind the glovebox, but didn't see it there. I did not remove the screws to the cover behind the glovebox because I wanted to first confirm where the switch is located.
Uh, the "blower switch" is the one you turn on the dash to control the blower speed. If you don't know where it's located, you probably should take the truck to a shop for repairs.
Uh, the "blower switch" is the one you turn on the dash to control the blower speed. If you don't know where it's located, you probably should take the truck to a shop for repairs.
No need for sarcasm, that's not what I asked for.
I'm here asking where the YH-1670 switch that I bought is located. I don't see where that means that I should take my truck to a shop for repairs.
So back to the original question, where is this switch located so that I can change it.
It's in the engine compartment on the passenger's side.
If you have a diesel look inboard of your vacuum reservoir and along the firewall. It is mounted in there with 2 screws. Disconnect the plug, undo the 2 screws, and viola, it's out. Inspect the connector and replace it if it's corroded so bad you can't clean it (you can buy a pigtail). I replaced mine earlier this year (fan speed #4 retired itself) and all 4 speeds are back.
If you don't have a diesel then start around where the passenger hood strut mounts to the front quarter panel and start looking inboard along the firewall. It's not the easiest to spot at a glance but it's there.
Is there anyway to tell if it's the switch or the resistor?
It could be either. Start with a visual examination of the connector on each. Frequently, the failure will be obvious (melted or severely discolored connector). If this is observed, you will also need to splice in a new connector which, unless you can solder, means you either learn how or you take it to someone who can. Unless you do this visual exam first, you'll probably start out wasting time, money, and energy on guesswork.
What does the switch do,
The switch controls which segment of the resistor assembly is switched in or out of the circuit. Blower speed is proportional to the current flowing through it (or the voltage applied to it, if you prefer) via the resistive divider except in position 4, which bypasses the resistor pack completely.