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How To: Troubleshoot 1997 V8 Blower motor

Discussion in 'Explorer, Ranger, A/C & Heater systems HVAC' started by OneLever, December 2, 2010.

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    1. OneLever

      OneLever Active Member

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      Part 1


      Hello everyone,

      This thread is intended to help Explorer and Mountaineer owners of only the year 1997 troubleshoot front blower motor failures. It was developed from working on a 1997 5.0L V8 Mountaineer and that is the only vehicle which I have tested it on. I am almost certain it does not apply to the later years of 1998-2001. This walk through focuses on the electrical side of the heating system. Please keep any discussion within this scope and post questions on the vacuum or AC systems in other appropriate threads. Because the 1997 V8 is the only year and engine combination I am familiar with it is the only one which I will answer specific questions on. For information related to the vacuum control side of the heating system see this thread by Turdle: Link.


      DISCLAIMER: All of my posts on the internet, including this walk through, are my opinions and are not intended as professional advice. I do not claim to be a professional in any way shape or form. I am not liable for any actions you take at all. Period. If you do not have basic electrical skills or an understanding of automobiles please do not attempt to replicate what I have done. It is quite easy to cause yourself problems if you do not know what you are doing.


      All of this testing was conducted outside with a temperature of 30 degrees Fahrenheit. After my hands went numb I stopped taking pictures. There are bound to be errors and omissions. Feel free to correct me or help improve the thread. My heating system as of this writing had no issues.


      Tools:
      With the pleasantries taken care of lets move on to what you will need:
      1. A multimeter with DC voltage and continuity test functions.
      2. An 8MM socket and ratchet.
      3. A paper clip or small diameter test leads. Relay blade inserts could also be used.
      4. A flashlight to see clearly.
      5. Some kind of plastic to hold back battery cables.
      6. A basic understanding of electronics.


      Symptoms:
      There are many symptoms of electrical failures. A general lack of the sounds the heating system makes when it usually turns on would be a first sign. If the heating system sounds like it is turning on and running but not directing the air where you expect it then you likely have a vacuum issue. If the heating system turns on but does not put out the right temperature air then you are probably looking at a Blend door issue. The electrical side powers the Blower motor and controls how fast it runs. When working correctly it blows air past the Blend door and across the Heater core. The air is then directed by a series of valves which are controlled by the vacuum system.


      Fuses:
      1. Start by disconnecting the Positive (red) battery cable from the battery and separating them so they do not make accidental contact. The terminal is held on by one 8MM bolt.
      Picture 1
      [​IMG]

      2. Second, check Fuse #6 (7.5 A Mini) in the Interior fuse panel. The fuses are labeled within the panel. If the fuse is blown there is most likely a short in the wires running to the Heater/AC Control switch in the center console or the switch itself may be bad.
      Picture 2: Interior fuse panel.
      [​IMG]

      3. Third, check Fuse #10 (7.5 A Mini) in the Interior fuse panel. The Rear blower motor relay, Blend door actuator, and the Temperature control potentiometer (switch) all run through this fuse. I will not discuss those circuits at this time.

      4. Locate the Power distribution box at the driver's side top rear of the engine bay.
      Picture 4: Power distribution box
      [​IMG]

      5. Open the power distribution box. There are tabs at the front and back.
      Picture 5: Power distribution box opened.
      [​IMG]

      6. Inside the cover of the Power distribution box are listed the numbers for the fuses. Look at this to locate Fuse #9 (50 A Maxi). Remove Fuse #9 and inspect it. If it is blown then you should look at the Blower motor resistor and possibly the Blower motor itself to see if they have gone bad. Also, the wiring to both these devices may have shorted out.
      Picture 6: Fuse #9 removed.
      [​IMG]


      Continuity Testing:
      My multimeter's continuity function checks to see if the resistance of a wire is below about 30 Ohms. So if you do not have a continuity function that may be useful to you. However, I think in reality the wires should measure a much lower resistance for the distances involved.

      Try re-seating the test leads or cleaning off the surface where they contact with a dry paper towel if you get a negative reading. Often times I would not get a correct continuity reading unless I was holding the test leads firmly in place. Please also be careful not to short out other circuits while testing the ones mentioned.

      We will now check the continuity of the circuit which provides power to the Blower motor when the Blower motor switch is placed on HI and the key is in the RUN position. Power flows through Fuse #9, the Blower motor relay, the Blower motor itself, the High speed blower relay, and finally to ground.

      Note: All continuity testing was conducted with the Positive battery cable disconnected and the key out of the ignition.

      7. Check continuity from the Positive battery cable (red) to the inboard blade receptacle of Fuse #9 in the Power distribution box. Note: battery cable not battery terminal.
      Picture 7a: From Positive battery cable.
      [​IMG]
      Picture 7b: To Fuse #9 inboard blade.
      [​IMG]

      8. At this point we will need to access Relay box #2 located at the passenger's side front of the engine bay about midway down.
      Picture 8: Relay box #2 location.
      [​IMG]

      9. Remove the Air cleaner hose. It is held onto the Air cleaner housing and the Throttle body by two 8MM screw type clamps. It has one electrical connection and one vacuum connection. Block off the openings you create to prevent contamination.
      Picture 9: Air cleaner hose removed.
      [​IMG]

      10. Remove the top of the Air cleaner housing. It is held on by two latches on the inboard side. The MAF is connected to this so set it aside in a clean location. There is only one connection for the MAF to it. Remove the Air filter as well so any small items you drop won't be sucked into the intake next time the engine starts.
      Picture 10: Air cleaner housing removed.
      [​IMG]

      11. Now you can easily access Relay box #2.
      Picture 11: Relay box #2.
      [​IMG]

      12. Open Relay box #2. The cover is held by tabs in the front and back. The Unknown relay was not listed in my manual and is possibly a spare. If your relay box does not look like this stop and do not continue using this walk through for wiring information. As your wiring is likely different.
      Picture 12: Relay box #2 layout.
      [​IMG]

      13. Remove the Blower motor relay. On the underside of the relay are printed the numbers for each pin.
      Picture 13: Blower motor relay removed.
      [​IMG]

      14. Check continuity from Fuse #9 outboard blade receptacle (in Power distribution box) to Blower motor relay Pin 87 receptacle (in Relay box #2).
      Picture 14a: From Fuse #9 outboard blade.
      [​IMG]
      Picture 14b: To Blower motor relay Pin 87.
      [​IMG]

      15. Locate the Blower motor electrical connector on the passenger side rear top of engine bay.
      Picture 15: Blower motor connector.
      [​IMG]

      16. Detach the Blower motor connector. It is difficult to access and may require a flat head screwdriver to release.
      Picture 16: Blower motor connector detached.
      [​IMG]

      17. Check continuity from Blower motor relay Pin 30 receptacle to Blower motor connector Pink/White wire (outboard in this photo).
      Picture 17a: From Blower motor relay Pin 30.
      [​IMG]
      Picture 17b: To Blower motor connector Pink/White wire.
      [​IMG]

      18. Remove the High speed blower relay in Relay box #2.
      Picture 18: High speed blower relay removed.
      [​IMG]

      19. Check continuity from Blower motor connector Brown/Orange wire (inboard in this photo) to High speed blower relay Pin 30 receptacle.
      Picture 19a: From Blower motor connector Brown/Orange wire.
      [​IMG]
      Picture 19b: To High speed blower relay Pin 30.
      [​IMG]

      20. Check continuity from High speed blower relay Pin 87 receptacle to the Negative battery cable.
      Picture 20a: From High speed blower relay Pin 87.
      [​IMG]
      Picture 20b: To Negative battery cable.
      [​IMG]

      Were all the continuity checks good? Are all the fuses shown above good? If so and your Blower motor does not come on when the Blower motor switch (in center console) is placed on HI with the ignition in RUN. Then you need to start troubleshooting the Blower motor relay, Blower motor, and High speed blower relay. The Blower motor resistor is not a part of the circuit in that configuration so it can be ruled out. If the Blower motor switch is placed in any position besides HI the Blower motor resistor becomes part of the circuit.

      If a continuity check came back negative repeat it to confirm your results. If it is still negative you are probably looking at a broken wire or loose connection. Where the wires connect to relay box and fuse panel receptacles can be an issue. If the connections at the relay box or fuse panel are just loose you can try re-seating them and securing them in place. If the terminals of the wires are not the issue then the wire itself may be broken. Fixing that will require running a replacement wire of the proper gauge and disconnecting the old faulty wire. I will not go into that because people of proper background should be able to figure it out and each case will be different.


      END OF PART 1
       
      Last edited: December 2, 2010
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    3. OneLever

      OneLever Active Member

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      I will be expanding on the above How To later on. For the next few days I will not have enough time to do so though. So it may be awhile.
       
    4. OneLever

      OneLever Active Member

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      Part 3: This post reserved for future additions.
       
    5. OneLever

      OneLever Active Member

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      Part 4: This post reserved for future additions.
       
    6. Kevin Barry

      Kevin Barry Member

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      Excellent write up.

      May I add that using the multimeter to confirm voltage (when battery is still connected) at the blower plug is also a good idea. Then check continuity at the plug.

      Also as a quick check, you can run power to the blower motor from the battery and ground to the car to see if blower motor itself works.



      My issue was the #30 slot on the blower motor relay. The plug and wire fell out of the slot causing no connection with the relay. I was getting 12.5V at the blower when grounded to the car. Nothing in the plug before fixing.

      This definitely qualifies as a sticky IMO.
       
      Last edited: December 2, 2010
    7. BouExplorerTwice

      BouExplorerTwice New Member

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      On my 1995, I'd lost the function of one of the fan speed settings and assumed it to be a blower resistor. It wasn't.

      After much similar troubleshooting, I finally found the trouble to be a burned out relay module located in a relay block in the front passenger side of the engine compartment, just in front of the air filter area. The dealer parts guy says there are pretty much only two relay modules; one cost about $7 and the other was about $12. I took mine out and swapped a new one in. Voila, instant fan-speed fix. I took the unused relay module back for unused refund.

      Seems like this easy-to-do fix should be looked at early in the troubleshooting before things get more complex; could save a lot of trouble. Now I know....
       
    8. andrusdragon

      andrusdragon New Member

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      many thanks

      This thread was exactly what I was looking for and verified that a relay was at fault. Thanks for saving me money so that I was able to fix this myself.
       
    9. BouExplorerTwice

      BouExplorerTwice New Member

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    10. tsizemore

      tsizemore New Member

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      Thanks for the post I found broken wire at the relay block on the #87 post

       

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