Blower Motor Switch

[Mike Wenrich]

After completing the blend door epic job I noticed the blower switch which has four positions is not working on position three, the next to highest fan speed. Actually I noticed it before the rebuild but chocked it up to blend doors. Question is what might be the problem? Just the switch or maybe the motor module next to the blower. The motor works fine in all other positions.

 

[BigPapa]

Either the resistor or the switch, probably the resistor, most common.

 

[Yo Hoot]

I have that issue. Changed the resistor.. didn't fix it. Switch is next

 

[BigPapa]

 

[Ozymandias]

I got a resistor from the big A last year as I was in need, I have chosen the one with the metal case around the brick. Works flawless for just a couple dollars.

 

[Mike Wenrich]

I hope the switch is still available if that's it but really not having the one position of the fan is not a huge problem. If I'm thinking correctly it's likely the switch as the resister would probably not work on all positions rather than just one of the four.

Got into the next blend door job yesterday on a 2003 1/2 ton Laramie. Plastic dash is in pieces and was already falling apart so it's not just me. Need to look on line today for options on that besides OEM. But she tells me the truck was not getting heat or cooling and the first set of doors I see are not broken. Will be splitting the plenum today to see if the others are bad but now I'm suspecting either actuator motor problems or maybe some other blockage. Further to follow.

 

[Mike Wenrich]

Found at least part of the problem. The A/C condenser was almost entirely blocked. Tried blowing it out but was having a difficult time with that. Looked like maybe a small amount of oil seepage so purchased a new one. One blend door broken but I believe the lack of air and heat was from the condenser being blocked. Got the plenum back together but now I'm trying to figure out how I can make the actuators work before putting it back in the truck. Just in case one is bad or I did anything incorrectly. The new condenser was a tight squeeze with different insulation than factory.

 

[brucejohnson]

Mike,
I found a 2005 diagram which should be the same as your 2004.5.
Maybe you could use this to do a continuity check of the resistor and or the switch.

 

[petersonj]

The A/C condenser was almost entirely blocked.

One blend door broken but I believe the lack of air and heat was from the condenser being blocked.

The new condenser was a tight squeeze

I was having a hard time following this post..., then I realized I think you mean "evaporator" not "condenser"?

- John

 

[Mike Wenrich]

Yup. I'm old, forgetful and now tired from working on this. Thanks for the reminder. It's not the first time I have struggled with the two in that plenum. Like heater radi...no evap...no core. The condenser is on the motor side I believe. Need to put labels on them if I'm going to tell anyone else what I am dealing with. As for the road map...er diagram, thanks for that. At least now I know it's fairly easy to get to the back of the switch by removing the face panel.

 

[CharlesinGA]

I thought I posted in this, but do not see it. Anyhow, it cannot be the resistor. If the coil that is in use during the med2 setting (next to high blower) were burned out, then NONE of the lower speeds would work. Low speed is all three resistors, Med1 (next to low) is the middle resistor in the drawing PLUS the one on the left and Med2 (next to high) which you say is the one that is inop) is the left most resistor only.

Charles

 

[Mike Wenrich]

So...I gather you believe it's the switch?

 

[brucejohnson]

I thought I posted in this, but do not see it. Anyhow, it cannot be the resistor. If the coil that is in use during the med2 setting (next to high blower) were burned out, then NONE of the lower speeds would work. Low speed is all three resistors, Med1 (next to low) is the middle resistor in the drawing PLUS the one on the left and Med2 (next to high) which you say is the one that is inop) is the left most resistor only.

Charles

Unless the union from M2 switch plug to the resistor pack union is open...That's where a continuity check of the wiring from the switch to the resistor pack comes into play.

Power OFF.

Remove the plug from the resistor pack.
On the resistor pack measure continuity from Pin 2 to Pin 4.
Should be a resistance value.
Then between Pin 2 and Pin 1.
Should be a greater resistance value.
Then between Pin 2 and Pin 3.
Should be the greatest resistance value.

You could do the individual Resistor values by measuring Pins 2 and 4; Pins 4 and 1; and Pins 1 and 3 of the resistor pack.​

On the wiring harness plug measure continuity of Pin 4 to any good ground while switching the fan switch through each position.
All but position 2 should read an open.
Position 2 "should" read less than 1 ohm (continuity). I believe the FSM says up to 3 ohms in general is considered adequate.

This should pinpoint where the problem exists - Resistor pack - Switch - Specific associated wiring route.

 

[Mike Wenrich]

Got it. Will try this this week.

 

[sag2]

You can drive the actuator in both directions using a 9 volt battery. Just reverse the leads to change direction.

 

[Mike Wenrich]

Now that is interesting. When I was doing the second blend door job I was not familiar with the pre-work operation of the doors. So I hooked up a 12V battery to test the five actuators before placing the plenum back in the truck. I was only able to get the doors to move one direction but at least it told me they were working. Could not understand why they would not move the other direction. I would have been afraid to try putting the ground wire on the + side of the wiring and had no idea a 9V battery would be sufficient to move the doors. Appreciate the tip and your comment should probably be in the TDR for other do-it-yourselfers. Electricity moves in strange ways. Like Zap, Pop! Damnit!

 

[Ozymandias]

You are a challenger then, not all systems in the truck run with 12V, there are many 5V circuits as well and like here 9V. Be careful.

 

[Mike Wenrich]

Not a challenger. I just learn things the hard way. Or sometimes on TDR.

 

[brucejohnson]

Now that is interesting. When I was doing the second blend door job I was not familiar with the pre-work operation of the doors. So I hooked up a 12V battery to test the five actuators before placing the plenum back in the truck. I was only able to get the doors to move one direction but at least it told me they were working. Could not understand why they would not move the other direction. I would have been afraid to try putting the ground wire on the + side of the wiring and had no idea a 9V battery would be sufficient to move the doors. Appreciate the tip and your comment should probably be in the TDR for other do-it-yourselfers. Electricity moves in strange ways. Like Zap, Pop! Damnit!

It is a DC (direct current) thing... and learning experience. Current flows one way...reverse polarity, and current flows the other way. Motor reacts accordingly.