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Steve, Auto Service Technician
Category: Car
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Experience:  25+ yrs experience as a professional working technician; ASE L1 master technician
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FORD EXPLORER: EDDIE BAUER..THE AC FAN ONLY WORKS..CONSOLE..RESISTER

Customer Question

I HAVE A 96 EDDIE BAUER FORD EXPLORER. THE AC FAN ONLY WORKS ON HI. I TOOK THE CONSOLE APART AND FOUND THE RESISTER BANK AND THE ROTARY SWITCH. THE DEALER SAYS THE RESISTER BANK IS $144.08 AND HE DOESN'T SHOW A LISTING ON THE SWITCH. ARE EITHER ONE OF THESE LIKELY TO BE THE PROBLEM AND, IF SO, HOW CAN I FIND OUT WHICH ONE,IF EITHER, BEFORE I BUY THE PART. IF IT IS THE SWITCH, DO YOU HAVE A PART NUMBER AND PRICE?
Submitted: 9 years ago.
Category: Car
Expert:  Steve replied 9 years ago.
  







Blower Motor Resistor

   Blower Motor

      Resistor
4L5Z19A706AA
$16.45
Notes 

   Auxiliary Heater & AC
4L1Z19A706AA
$13.20
Notes 

 





Labor
Skill
Level

Warranty
Standard

Blower Motor Resistor

   Replace

      Blower Motor
B
0.3
0.5
Notes 

My information does not list a separate fan switch for this model; it may be part of a control assembly which would explain the high cost.


Blower Motor Speed Control

The blower motor is controlled by a four-position heater blower motor switch located on the left side of the control assembly. The four positions are LOW, MEDIUM LOW, MEDIUM HIGH and HIGH. The four operating speeds are obtained with a heater blower motor switch resistor connected in series with the heater blower motor switch operating on the ground side of the blower motor.

With the function control knob in the OFF position, the blower motor will not operate.

With the heater blower motor switch at LOW, current flow in the ground circuit is through three resistors to obtain the lowest operating speed.

With the heater blower motor switch at MEDIUM LOW, current flow in the ground circuit is through two resistors to obtain a medium low operating speed.

With the heater blower motor switch at MEDIUM HIGH, current flow in the ground circuit is through one resistor to obtain a medium high operating speed.


   The way it all works is as follows:


Power is supplied to the blower motor from the blower motor relay on the pink/white wire.    This part of teh circuit is OK, if it works on high speed.


   The ground is switched through various resistor combinations to control low speeds.


the black wirte from teh AC control assembly is the ground source for teh circuit.  The AC control connects this ground to teh blower switch through the red/ orange wire to the blower switch.  The blower switch then connects the ground circuit to the lg/w, y/rd wires to pass through one or 2 resistors dependinon speed selected.   The orange/blk wire from the switch to the resistor bypasses the resistors and dirrectly grounds the circuit for high speed operation.  There is a thermal limiter (fuse) built into the resistor block itself.


   On medium speeds with everythign conencted, check for power at teh y/rd or lg/w wires at the resistor; if there is no power present there, then the resistor is probably open and likely the source of teh problem.   Resistors fail much more often thatn control switches due to heat, moisture, and vibration present in the heater case.













Expert:  Steve replied 9 years ago.

 I see the first part of my posting did not display: it was a part # XXXXX price for a resistor for your vehicle.  It read as follows:


4L5Z19A706AA  (front  blower resistor assy)    $16.45


 

Steve, Auto Service Technician
Category: Car
Satisfied Customers: 5494
Experience: 25+ yrs experience as a professional working technician; ASE L1 master technician
Steve and other Car Specialists are ready to help you
Expert:  Steve replied 9 years ago.
   If you are having any difficulty in diagnosing this problem, let me know at waht point in the circuit you are losing power and I can try to help you diagnose it...
Customer: replied 9 years ago.
IN FURTHUR STUDY OF YOUR ANSWER, YOU SAY THE CONTROL IS ON THE LEFT SIDE AND INFER THAT THERE ARE FOUR SPEEDS AND THREE RESISTERS. MY SPEED CONTROL IS ON THE RIGHT SIDE AND I APPEAR TO HAVE 12 OR 13 DETENTS ON MY SWITCH. I ALSO HAVE 4 RESISTERS.
Expert:  Steve replied 9 years ago.

 The information provided for your vehicle does not mention which side of the veihicle any of these componets are located on; when it mentions "ground side" it is referring to the fact that the circuit is swithed on the ground side, that is in between teh load (motor) and battery negative (chassis ground) in the circuit... it doesnt refer to any particular location of components...


   Do the wire colors mentioned in the procedure match the wire colors on the vehicle?

Expert:  Steve replied 9 years ago.

   A fan switch never has 12 or 13 detents, as there are not that many wires to select in the circuit...    are you sure what you are referring to as the switch is the fan switch, or is it a climate control system, where the switch is controlling more than blower speed?

Expert:  Steve replied 9 years ago.

    From your original description of the vehicle, it is inferred that it is a manually controlled AC system;  you mention having found the resistor block.  If it is a climate control (automatic) system, then there is not resistor block in the system; it is microprocessor controlled and the diagnostic procedure is very different...


   On an automatic system, you will need to begin by entering the self diagnostic mode and retrieving any failure codes stored in it's memory.   


this is done as follows:


EATC On Board Diagnostics Test



  1. Record all diagnostic trouble codes (DTCs) displayed during test.



    • The control assembly will detect electrical malfunctions occurring during the on-board diagnostic.
    • Ensure that the engine is warm (at least 49°C [120°F]) coolant temperature). To display the DTCs for the malfunction detected, initiate the on-board diagnostic by pushing OFF and FLOOR simultaneously and then AUTOMATIC within two seconds. The test may run as long as 20 seconds, during which time the display will be blank. If the display is blank for more than 20 seconds, go to General A/C System Diagnosis When On-Board Diagnostic Test Indicates NO ERROR.
    • The On-Board Diagnostic Test can be initiated at any time with the resulting DTCs being displayed. Normal operation of the system stops when on-board diagnostic is activated. To exit the on-board diagnostic and restart the system, push the BLUE button. Pushing the DEF button instead of the blue button will clear all DTCs. The on-board diagnostic should be deactivated before turning the system OFF Refer to the DTC chart for an explanation of DTCs. See: Trouble Code Descriptions


  1. If a malfunction exists but no DTC appears during the test in Step 1, refer to the appropriate symptom(s) in the Symptom Chart. See: Diagnosis By Symptom\Electronic Climate Control

 


Expert:  Steve replied 9 years ago.

 An important diagnositc clue also:


Does the blower operate at high speed in all positions, or is it on high in high position, and off in all other positions?

Customer: replied 9 years ago.
THE RESISTER BANK HAS 4 RESISTERS ON IT.IT LOOKS LIKE ONE END OF EACH RESISTER IS CONNECTED IN SOME HIDDEN CONFIGURATION TO A CLUSTER OF 5 WIRES THAT GO TO THE FAN- YELLOW, BLUE, BLACK, WHITE AND RED. THERE ARE RED AND WHITE WIRES COMING FROM THE OPPOSITE END OF EACH RESISTER THAT GO TO A PLUG WHICH PLUGS INTO THE CONTROL BOARD. THIS PLUG HAS 4 RED AND 4 BLACK WIRES.

THE 11 OR 12 POSITION THUMBWHEEL TYPE FAN SWITCH PLUGS INTO THE CONTROL BOARD WITH A BLACK,A GREY AND A BLUE WIRE. THERE IS ALSO A SMALL INDICATOR LIGHT THAT IS INCORPORATED INTO THE SWITCH ASSEMBLY AND ITS WIRES ARE INCLUDED IN THIS PLUG.
Expert:  Steve replied 9 years ago.

 If it is a thumbwheel controlled fan switch, then you have an automatically controlled system; preforming the diagnostic self test procedure as detailed in the last response should generate service codes to help diagnose the source of the failure.


   What kind of test equipment do you have available to you at teh moment; do you have a DVOM, a 12 volt test light, or some other way of testing for power and ground at various poiints in the circuit?

Customer: replied 9 years ago.
Reply to Steve7654's Post: THE BLOWER ONLY COMES ON WHEN YOU BUMP THE THUMBWHEEL AGAINST THE HIGHEST SETTING END OF TRAVEL OR IF YOU PUSH THE MAX AIR BUTTON. IT IS LIKE IT PULLS IN A RELAY WHICH SEALS ITSELF IN. IF THE TEMPERATURE GOES ABOVE THE SETTING THE UNIT CYCLES OFF. IT THEN WILL COME BACK ON HIGH WHEN THE THERMOSTAT CALLS FOR COOLING.
Customer: replied 9 years ago.
THE CODE WAS 888. I HAVE A DVM BUT I HAVE TO GO AND GET IT IF I NEED IT.
Customer: replied 9 years ago.
I ALSO NOTICED THAT WITH THE FAN ON HI, IF YOU MOVE THE THUMBWHEEL 1 DETENT, THE FAN GOES OFF.
Expert:  Steve replied 9 years ago.
 If you have the resistor bank out in your hand, try turning the blower on to one of the lower speeds and checking for power at the resistors in the bank.   as you cannge blower speed settings, the power feed should move to various resistors in the bank as they are switched into the circuit.   If you are not measuring any power to the resistors, then the control unit is faulty.   If you are measuring power coming from the control unit to teh various resistors, then check the ground circuit to the resistor block for an open.    You can diectly check teh resistor block itself if you ahve a DVOM; set it to ohms, and look for continuity from one end of the block to the other; you should not find an open circuit.
Customer: replied 9 years ago.
I HAVE A 96 FORD EXPLORER EDDIE BAUER WITH AUTOMATIC CLIMATE CONTROL. THE FAN ONLY WORKS ON HI. THE THUMBWHEEL POTENTIOMETER READS 4.5K OHMS ACROSS THE WHOLE RESISTER AND THE TAP VARIES FROM 600 OHMS TO ABOUT 4.5 AND GOES DOWN TO ABOUT 18 OHMS WHEN IT MOMENTARILY TOUCHES THE HIGHEST SPEED SETTING BEFORE DROPPING BACK TO 600. WHEN IT TOUCHES THE HIGHEST SPEED SETTING (18 OHMS) THE FAN COMES ON AND LATCHES ON HIGH. IF YOU MAVE THE THUMBWHEEL A DETENT OR TWO THE FAN GOES OFF. IT WILL COME BACK ON HI IF YOU PUSH MAX AIR OR BUMP AGAINST THE HIGHEST FANS SETTING AGAIN.
I CHECKED THE RESISTER BANK AND THEY ALL READ 58 OHMS. I UNPLUGGED AND REPLUGGED BOTH PLUG ASSEMBLIES AT THE BACK OF THE MAIN CONTROL UNIT.
I PUSHED OFF AND FLOOR AND THEN AUTOMATIC AND AFTER 15 OR 20 SECONDS THE CODE "888" CAME UP. WHAT DO I DO FROM HERE TO FIX THIS THING? I DON'T SEE ANYTHING ELSE TO FIX UNLESS IT IS A REMOTE TEMPERATURE SENSOR OR SOMETHING.
Customer: replied 9 years ago.
THE AUTOMATIC CLIMATE CONTROL FAN ONLY RUNS ON HIGH. IT DOESN'T MATTER WHERE THE THUMBWHEEL IS SET, IF YOU PUSH MAX AIR, IT GOES ON HIGH. IF YOU MOVE THE THUMBWHEEL, THE FAN GOES OFF. IN THE AUTOMATIC MODE, THE FAN WILL ONLY COME ON IF YOU PUT THE THUMBWHEEL TO THE HIGHEST POSITION AND THEN PUSH IT A LITTLE FURTHUR AGAINST THE SPRING WHERE IT LATCHES IN THE FAN CIRCUIT , AGAIN, ONLY ON HIGH. IF YOU TRY TO TURN IT DOWN, AS SOON AS THE THUMBWHEEL MOVES TWO OR THREE DETENTS, THE FAN GOES OFF. I TOOK THE THUMBWHEE OUT AND THE FULL POTENTIOMETER'S FULL RESISTANCE MEASURED ABOUT 4.5 K OHMS. THE TAP VERIED BETWEEN 600 OHM AND 4.5 K OHMS. WHEN BUMPED AGAINST THE SPRING RETURN AT THE HIGHEST POSITION, THE TAP WENT TO 18 OHMS. I CHECKED THE POWER RESISTERS AND EACH ONE MEASURED 58 OHMS. I RESEATED BOTH PLUGS IN THE BACK AND COULDN'T FIND ANYTHING ELSE TO CHECK WITHOUT A WIRING DIAGRAM. I RAN THE ON BOARD DIAGNOSTIC AND THE CODE 888 CAME UP BUT I DON'T KNOW WHAT THAT MEANS. IF YOU KNOW HOW TO FIX THIS PLEASE HELP ME BECAUSE THAT HI FAN IS DRIVING ME CRAZY.

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