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Saturday, November 3, 2012

No High Blower Speed 2002 Chevrolet Silverado

2002 Chevy 2500HD with manual air.  I lost only speed 5 on the blower and ordered a relay & harness from The Electric Connection and replaced this last weekend with no change.  The fuse was good under the hood but I changed it just for grins and it too had no effect.  Also, I cannot find a fuse labeled exactly "BLWR" but all fuses are good.  I have 12 volts going into the blower motor inself on all 5 speeds but it just quits working when the switch is changed to speed 5.  Could this be the switch?
Thanks for any help in advance!

Hi GH,
You have to have three things in order for blower speed number 5 to work. Ground on terminal "E" black wire, Power on terminal "F" orange wire and Power on terminal "G" red wire. Wire colors are for original wiring.  Terminal "E" ground id constant and terminal "G" power is constant. Terminal "F" power is only there when the ignition is on and the blower switch is set to position 5.


Ok Sparky,

Power to terminal F is good when the switch is on 5. Terminal E ground seems good. Power on terminal G is good through all 5 speeds and when the switch is off. However, this is when it is checked with the harness disconnected. When reconnected, power to terminal G is lost when the switch is on speed 5. Using a test light and the harness plugged in, terminal G will go out when switched from 4 to 5 and not necessarily come back on when switched back to 4 even though the blower starts again. If someone simply pushes down hard on the underhood fuse and holds it down, the light will come back on as long as the switch is anywhere but 5. If you leave it alone and check a little later, it usually will light up again (terminal G) but immediately go out again when switched to speed 5. Any thoughts?

Hi GH,
It would seem that you have either a faulty fuse box,  fuse or a loose harness connection on the underside of the fuse box. Some fuse boxes have securing bolts that are tightened on the upper side of the fuse box and some have the securing bolts underneath. Either way they will have to be removed and inspected for damaged terminals.


I've found the source of the problem.  I've attached a photo in case you run across this situation again.  Everything I found on the internet about speed 5 not working was either a fuse in the underhood fuse box or the blower resistor and mine was neither.  I was reading on the net that other people were having the same problem and nobody ever answered them concerning what I found.  Now my problem is how to fix the situation correctly.  Does have a replacement 68-pin fuse box connector like the one in the photo?  If not, would this even be available at the dealer?  If not, would you get one from a junk yard or simply bypass the damaged terminal with an inline fuse?  The fuse box itself appears fine and if a replacement connector is advised by you, I know I would have to replace the one burned wire and its terminal and I am able to do so.  Thanks again for your help.  I will use for all my electrical parts needs in the future due to the fabulous experience I've had!

Hi Glenn,
I think that rewiring the damaged circuit to an external fuse holder will be the best option.



Anonymous said...

I had the same problem. The hardest part about diagnosing was that if you unplugged the blower fan and tested the two wires coming from the resistor there was power on speed 5. So it seemed to pass every test, But what you do not realize is that if the fan is plugged in then it draws enough power to lose its connection at underhood fuse and fail to run on speed 5.

lms659 said...

I have a 2002 chevy blazer and through reading here I went to check the fuse box under the hood and found that it was melted and one the "prongs" that would hold the fuse in place was gone ..can this be replaced? or how hard is it to replace the whole box? I have no heat on the floor all the rest is fine..I have replaced resistor already. Just not sure if this is something I should take to a mechanic.

Sparky said...

The fuse box itself is not cost effective to repair. The box should be fairly easy to replace. I believe that all of the connectors are either clipped in or held in place by screws. I would recommend checking with your local dealership to see if it is still available and if not how many options were used fro your vehicle. That way you will have an idea of what to look for in a used one.