DryCreek

Quick question for those of you with an '03 wiring diagram. The blower on my wife's truck seems to only have 2 speeds now - low and high. Over the past few years I have noticed that the #3 position seemed to blow at the same rate as the #2 position, and of course the #1 and #4 positions worked as they always had. This weekend we were headed back from Abilene and it now seems like the #2 position is running at the same speed as the #1 position.

Do these trucks have a separate fan speed controller (i.e. resistor bank) or does the speed selection occur in the blower motor?

Just need to know what to order.

Thanks

Dry creek

Bark

BLOWER MOTOR RESISTOR
BLOCK
DESCRIPTION
The blower motor resistor is mounted to the rear
side of the HVAC housing on the passenger side of
the vehicle.
OPERATION
The resistor is a ceramic resistor that utilizes
resistor circuit tracers to reduce current flow to the
blower. The blower motor switch directs the ground
path through the correct resistor circuit to obtain the
selected speed.
The blower motor resistor cannot be repaired and,
if faulty or damaged, it must be replaced.
DIAGNOSIS AND TESTING - BLOWER MOTOR
RESISTOR
For circuit descriptions and diagrams, (Refer to
Appropriate Wiring Information).
WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS,
DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE
THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM
CAPACITOR TO DISCHARGE BEFORE PERFORMING
FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS
COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect and isolate the battery negative
cable.
(2) Reach under the passenger side bottom of the
HVAC unit and unplug the wire harness connector
from the blower motor resistor.
(3) Check for continuity between each of the
blower motor switch input terminals of the resistor
and the resistor output terminal. In each case there
should be continuity. If OK, repair the wire harness
circuits between the blower motor switch and the
blower motor resistor or blower motor relay as
required. If not OK, replace the faulty blower motor
resistor.
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS,
DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE
THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM
CAPACITOR TO DISCHARGE BEFORE PERFORMING
FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS
COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect and isolate the battery negative
cable.
(2) The blower motor resistor is accessable from
the passenger side of the HVAC unit and is located
on the bottom of the HVAC unit.
(3) Pull out the lock on the blower motor resistor
wire harness connector to unlock the connector latch.
(4) Depress the latch on the blower motor resistor
wire harness connector and unplug the connector
from the resistor.
(5) Remove the two screws that secure the resistor
to the HVAC housing.
(6) Remove the resistor from the HVAC housing.
INSTALLATION
(1) Install the new resistor in the HVAC housing.
(2) Install the two screws that secure the resistor
to the HVAC housing and tighten to 2.2 N·m (20 in.
lbs.).
(3) Plug in the blower motor harness connector.
(4) Push in the lock on the blower motor resistor
harness connector.
(5) Close the glove box door.
(6) Connect the battery negative cable.
BLOWER MOTOR SWITCH
DESCRIPTION
The A/C Heater blower motor is controlled by a
four position rotary-type blower motor switch,
mounted in the A/C Heater control panel. The switch
allows the selection of one of four blower motor
speeds, but can only be turned off by selecting the
Off position on the blower motor switch.
OPERATION
The blower motor switch directs the blower motor
ground path through the mode control switch to the
blower motor resistor, or directly to ground, as
required to achieve the selected blower motor speed.
The blower motor switch cannot be repaired and, if
faulty or damaged, the entire A/C Heater control unit
must be replaced.
DIAGNOSIS AND TESTING - BLOWER MOTOR
SWITCH
For circuit descriptions and diagrams, (Refer to
Appropriate Wiring Information).
WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS,
DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE
THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM
CAPACITOR TO DISCHARGE BEFORE PERFORMING
FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS
COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Check for battery voltage at the fuse in the
Power Distribution Center (PDC). If OK, go to Step
2. If not OK, repair the shorted circuit or component
as required and replace the faulty fuse.
(2) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Remove the A/C Heater control from the instrument
panel. Check for continuity between the ground circuit
cavity of the A/C Heater control wire harness
connector and a good ground. There should be continuity.
If OK, go to Step 3. If not OK, repair the open
circuit to ground as required.
(3) With the A/C Heater control wire harness connector
unplugged, place the A/C Heater mode control
switch **** in any position except the Off position.
Check for continuity between the ground circuit terminal
and each of the blower motor driver circuit terminals
of the A/C Heater control as you move the
blower motor switch **** to each of the four speed
positions. There should be continuity at each driver
circuit terminal in only one blower motor switch
speed position. If OK, test and repair the blower
driver circuits between the A/C Heater control connector
and the blower motor resistor as required. If
not OK, replace the faulty A/C Heater control unit.
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS,
DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE
THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM
CAPACITOR TO DISCHARGE BEFORE PERFORMING
FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS
COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
The blower motor switch cannot be repaired and, if
faulty or damaged, the entire A/C Heater control unit
must be replaced. (Refer to 24 - HEATING & AIR
CONDITIONING/CONTROLS/A/C HEATER CONTROL
- REMOVAL)
INSTALLATION
WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS,
DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE
THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM
CAPACITOR TO DISCHARGE BEFORE PERFORMING
FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS
COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) The blower motor switch cannot be repaired
and, if faulty or damaged the entire A/C heater control
unit must be replaced(Refer to 24 - HEATING &
AIR CONDITIONING/CONTROLS/A/C HEATER
CONTROL - INSTALLATION).

Trying to remember where I saw a wiring diagram. When I find it I will post it.

Bark

Darn! I couldn’t find the wiring diagram in the post that I thought it was in. Oh well. Here are a couple of other posts but they may not apply to your year of truck.


https://www.dieseltruckresource.com/...resistor+block

https://www.dieseltruckresource.com/...resistor+block

https://www.dieseltruckresource.com/...resistor+block

https://www.dieseltruckresource.com/...resistor+block

DryCreek

I will take a look tomorrow morning. My bets are all on one or two of the resistors being open.

Dry Creek

Bark

Keep us posted.

Jeff in TD

In a nutshell, the fan motor gets + from the key switch, and the switch on the dash completes the - cirucit either directly (on high) or through the resister block on other speeds.

The resister block is mounted on the bottom of the HVAC box next to the fan motor above the passenger's foot area.

I'd also bet one of the legs on the resister block is open circuit.

DryCreek

Didn't get to it today - spent 3-1/2 hours trying to knock a hole into rock big enough to concrete a new gate post in. It seems that someone accidentally backed into it while trying to get too close with the shredder.
I learned my lesson!

Bark

LoL. Sounds like that same someone who backed into the lower garage door track at my place.

DryCreek

OK folks, here is what I found out:
The resistors were all good, what had happened was a thin layer of corrosion had built up on the M2 spade of the resistor block. This caused erratic readings whenever I used that point and compared to another point. I "borrowed" one of the wife's emery boards and dressed up the spade. Once reinstalled and tested all was well once again!
Thanks for the help guys.

Dry Creek

Bark

Cool!!

Blake Clark

Same problem, same solution fixed mine, Thank You for the info!

brandon mitchel

I bet the cause of your AC & Heater Control problem is the resistor. Most vehicles have the resistors in the evaporator case, so they are cooled by the A/C.

Jeff in TD

Yeah, it's mounted next to the fan on these trucks. If you have problems with the fan in every speed except high, that would point to the resistor.

akrammit

Bringing this back for a bit. I replaced my blower motor about three years ago. It just quit working. Now the one in it now quit working. I could tap it and it would work. so I took it out cleaned it up with electrical cleaner and oil the bearing and made sure to clean any excess up. It worked fine. Now a week later it quit working all together. I pulled it out used some jumper wires and nothing. Pulled the motor from the case and it worked great. I guess something somehow is a ground when installed int he vehicle. So Could it be the resistor? I thought that on high it bypassed the resistor and would at least work on high even if the resistor failed.A resistor up here isn't cheap and I hate to just throw parts at a problem to try and fix it. Oh and the temps are falling back to subzero soon and wont warm back up. So no heat is not good at all.

Jeff in TD

According to the diagram, when on high the resister block would not be in the circuit.