Heater Blower not working

cdnron · #1 10-20-2009, 09:31 AM

I don't have a wiring diagram for my '97 B2500...which isn't helping!

The fan itself runs fine if you jump power to it directly.

I've checked all my fuses with my meter...they are all fine.

I have power in and out of my dash fan switch.

There is a relay on the side of the blower box under the hood that sends power to the fan itself. It has power going into it but nothing coming out to the fan. Replaced the relay...no change. I took off the plastic cover and if I operate the relay manually the fan comes on...so it must not be getting any power to the relay coil...although I'm not really sure where that power is coming from.

There is also some device in the front of the heater box with leads that run back to the relay. Not sure what it is...looks like some sort of temperature control...cut off??? There is a clip on plastic piece which looks like it is there to direct air flow across these coils. It has 4 wire coils (2 "heavy" 2 "light" gauge) in it and one leg has no coil, but a resistor in it. One side of that resistor lead runs to (what appears to be) a "floating" connection to one of the larger wire gauge coils. That connection is totally corroded and I don't get any continuity between the two wires that join there. The other end of that resistor lead runs back into the blower relay...could this be my problem?

I'm thinking maybe this (if it is some sort of maximum temperature shut off?) is over-riding the fan controls and not allowing it to run???...or maybe this is where the relay coil power comes from?

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alloro · #2 10-20-2009, 07:22 PM

Quote:

Originally Posted by cdnron

There is also some device in the front of the heater box with leads that run back to the relay. Not sure what it is...looks like some sort of temperature control...cut off???

That's the blower motor speed resistor. It's like $15-$20 at the dealer. Replace it and your problem should be gone. If the plug or wires to it are melted then you can get a repair pigtail from the dealer as well. The part number for the pigtail is 5019941AA just in case you get an idiot that can't find it.

cdnron · #3 10-23-2009, 01:38 PM

Quote:

Originally Posted by alloro

Replace it and your problem should be gone. If the plug or wires to it are melted then you can get a repair pigtail from the dealer as well.

Unfortunately...

Replaced it, pigtail looks good, but still no fan...nada...nothing...not even on high speed.

Anybody got a wiring diagram? Seems like the power going to my blower relay is the problem.