HOW TO: modify your A/C heater control

Discussion in 'How To' started by roadrunner, May 10, 2005.

  1. roadrunner

    roadrunner Full Access Member

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    This mod will let you use the full range of your heater control without having to continuously run the fan motor. This conserves the fan motor bearings and electrical draw, while allowing a temperature controlled, fresh air flow through the cabin. Air flow will naturally depend on vehicle speed, but is noticable at all speeds and equivalent to fan position #1 at about 65MPH.

    In this procedure you will disable one of the fan positions (I chose position #4, high speed, because I used it least) by removing the appropriate connector pin. Here's the procedure:

    1. Remove the heater control, using the procedure in this section http://www.jeepkj.com/forums/viewtopic.php?t=1002&sid=79faa6e854d68b9c138b38948313dbfc

    2. Gently remove the back side of the control unit, lifting it over the snap pins. pull the pin selector knob off. The pin lay-out is as follows:

    [​IMG]
    Connector pin assignments ('04 control shown)

    3. To disengage the #4 fan position, gently pry the #6 pin off.

    [​IMG]
    #6 pin removed ('05 control shown)

    4. replace the pin selector knob and snap the back cover back on. The pins on your control unit will now look something like this:

    [​IMG]

    5. re-install the A/C heater control.

    Everything will now work as before, except the #4 fan position, which no longer exists. This is your new "vent" position.

    I have done this on both the '04 and '05 heater controls. The pin assignments are identical.

    A word of caution: Any A/C and/or defrost (which also employs the A/C) setting should have a continuous air flow across the heat exchanger for efficient use. For that reason, this newly created "vent" position would be appropriately used for heated and ambient air only.
     
  2. valkraider

    valkraider New Member

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    Cool tip!

    As far as your "word of caution": On my 2005, the owners manual states that the AC is on when the selector is in "Floor" mode, and that the AC is on when in "mix defrost" or "defrost" modes and the outside temp is below 30 degrees.

    We are working on a solution to the "force you to have AC on while in floor mode" problem...
     
  3. roadrunner

    roadrunner Full Access Member

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    It's deceptively simple to fix, and I apologize for not posting it earlier (didn't think anyone was interested). Basically, you cover that portion of terminal #2 over the "floor" position so the bezel contact can't make contact in that region. I also did it over the "floor/defrost" position, but you can customize any way you want. Here are the steps (sorry to say I lost my pictures of this procedure):

    1. Remove the back cover of the Heater Control
    2. Trace (what I call) the #2 terminal to the selector control (middle knob) zone. (#2 is the second skinny terminal from the end)
    3. Observe the contact zone as you rotate the selector knob over the "floor" position (or any position you want to block the automatic A/C). Mark this area off with a Sharpie or similar.
    4. Remove all dialectric grease from this area with a Q-tip. Don't discard the Q'tips.
    5. With your designated area thoroughly clean and dry (I used alcohol), attach a small piece of packing tape (I used the heavy duty 3-M tape). Trim it with a razor blade, etc. Better too much than too little -- you can trim a little at a time as you test the knob position with your multimeter (below).
    6. Using a multimeter, verify that there is no continuity between the #2 terminal and the center contact when it is in the "floor" position.
    7. With the smooth tape solidly in position, re-apply the dialectric grease over the tape.
    8. Close up the job and enjoy floor heat without your A/C running!! (whistle)

    Remember, you can still manually select A/C at any time in any position using the A/C button('05 and newer heater control)! \:D/
     
  4. omniphil

    omniphil New Member

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    That is great! I saw your how to the other day and I was thinking the same thing, I could trace #2 back to where it made contact and figure out how to disable from there.

    I was initially thinking tape as well but was wondering if the tape would wear down over time and allow a connection to come thru?

    I love the idea for disabling it in the floor/defrost mode too, thats great, that way you can get some hot air up in the windsheild without the AC. Tho I think I may disable it altogether for all modes and have the AC button turn on the AC manually.

    Do you think you can actually cut the metal strip before it gets up near the heater knob to disable it all together? or is there other things further down the metal strip that would not work if the strip was cut? Basically I was wondering if I could remove the connector for #2 just like you did with the #4 heat postion mod. And would that still allow the AC button to operate manually.

    Thank you for the how-to, As soon as we get our CRD back I am going out and disabling the "Auto AC" feature :)
     
  5. omniphil

    omniphil New Member

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    Ok, I answered my own question. We have a rental Liberty so I went ahead and took it apart for reference.

    If I bypass the #2 metal tab or circuit, the AC will not come on at all, the light on the AC button does but, no AC at all.

    Originally I tried to just remove the #2 wire from the connector harness, but it is needed. so you have 2 options, Do like the original posted stated by using thick tape to mask the areas on the metal contact bar that you dont want it to hit.

    Or, the second option. And what I'll end up doing is unsolder the back side of that #2 bar (where it goes up and into a circuit board) and bend it down out of the way so that that bar becomes inactive. Then I will take the #2 wire out of the connector and run a jumper wire from that to where the bar used to go, completing the circuit for the AC button to operate manually. You could also just cut out a potion of the metal bar and solder a jumper wire across it as well, but that will be hard to put back to stock if need be.

    Clearly the original posters method is far easier. I am just concerned with wear over time on the tape. And then if it does start turning the AC on, i will never know really. By deactivating the bar from the circuit, I can gaurantee it will never come on down the road.

    In either case, we now have a solution! yay!

    Thanks go to the original poster for sparking this idea.

    If theres anyone in the Southern NH area that wants this mod done, I can perform it for you, I know alot of people aren't comfortable around a soldering iron.
     
  6. valkraider

    valkraider New Member

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    If wear is concerned, how about gluing a small piece of plastic instead of using tape? Maybe something from a craft store.....
     
  7. roadrunner

    roadrunner Full Access Member

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    I considered cutting, but didn't want to risk jeapordizing the structural integrety of the copper piece. Also, it would have been irreversable. Finally, I didn't want to interrupt the contact plane on the knob armiture.

    I considered an epoxy layer with plastic over it. But then, after thinking about it, wondered if plactic tape wasn't virtually the same thing.

    In the end, the thicker packaging tape became the choice of the day -- fast, easy to trim, reversable and re-modifyable. I ended up using Scotch Packaging "Super Strength" tape (not 3-M as earlier reported). I use these tapes a lot and find them to be quite tough.

    As an experiment, I passed a high friction pencil erasure across a sample of tape 2000 times and didn't breach the tape. Just wore my arm out. I was impressed. I can't imagine the selector armiture being harsher than that!

    Still, don't know how long the tape will last. If in doubt, you can always go for 2 layers! But it's a work in progress -- we'll see. These other ideas are definitely worth exploring also! :-k
     
  8. Bennett

    Bennett Active Member Administrator

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    [​IMG]

    I was thinking about putting a switch on pin 6 to turn ac on or off...

    Think that would work?

    Bennett
     
  9. roadrunner

    roadrunner Full Access Member

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    Looking for a more realistic test, I passed a smooth stainless knife handle butt over a sample of the tape using about (according to the postal scale) 1 lb. of force, with no dialectric of friction modifier.

    At 6000 passes, the tape definitely looked worn, but was still intact. IF that's a reasonable simulation, then: if you used the switch 4 times daily every day for 6 months out of the year, one layer of tape should last at least 8.22 years. I'm satisfied. Two layers of this particular tape should certainly be considered as a long term fix!.
     
  10. roadrunner

    roadrunner Full Access Member

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    Yes. In that case you would leave the factory A/C switch on all the time and use your auxillary switch as the A/C switch.

    BTW, my numbering system is upside down from the factory version (whoops), but otherwise compatable.

    Hey Bennett, did you get the new style heater control to operate correctly in your '02? I recall that you had some initial concern.
     
  11. omniphil

    omniphil New Member

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    That would definately work. In my testing I removed Pin 6 from the connector and the AC would not turn on at all. Also the AC button would not function. (although the light does light up)

    What I'm going to do is remove that pin 6 from the connector and run a jumper wire to inside the control unit and solder it to where the end of that metal bar is connected. at the same same unsoldering the bar from the end, this was the bar stay intact, but it no longer conductive.

    This way I can have the AC off all the time, but I can simply hit the AC button to turn it on for defrost as needed. The way cars used to work before auto manufactures decided we aren't smart enough :)
     
  12. valkraider

    valkraider New Member

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    Now THIS is dedication. :)

    I think I would get to maybe 100 and say - hmm, looks good enough for me...
     
  13. omniphil

    omniphil New Member

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    Borderline obsessive, lol. Joke...

    Seriously tho, thats way above the call of duty, good job!
     
  14. Bennett

    Bennett Active Member Administrator

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    Now that's what I call engineering!!
     
  15. omniphil

    omniphil New Member

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    Its also probably worth noting for the folks that don't know.

    One of the reasons the AC runs when you dont really want it is because running the AC lubricates the entire AC system (There is oil in the refrigerant), Something that needs to be done on a regular basis to prevent seals from prematurely failing.

    So by have the AC coming on automatically during the winter basically the system stays lubricated all year round and AC failures are less common. This is one of the reasons all modern vehicles use this type of logic. For reliability.

    If you are using one of the modifications in this thread to bypass the AC, make sure you manually turn it on every couple of weeks or so for 5-10 minutes or so to lubricate the system and prevent failures.

    Just an FYI....
     
  16. yoda13

    yoda13 Full Access Member

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    Sounds like good advice to me... =D>
     
  17. valkraider

    valkraider New Member

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    I also wanted to allow for vented airflow, with the fans not running. But I felt that removing the fan speed 4 was not very intuitive to the user. I agree that we rarely if ever use fan speed 4, but it makes no sense to switch the fan to "4" to turn it off.

    Instead of removing fan speed 4 (as this uh, "reused" picture actually shows fan speed 4 removed - see previous posts) , I wanted to keep all my fan speeds but add a fan speed 0.


    [​IMG]

    Positions ABCD and EFGH are ground connections.

    The back "knob" connector is made up of three contacts on a disk. These contacts slide around making contact with the plate locations shown in the picture. At any given time, two contacts are touching ground, and one contact is touching the fan speed. Since this image is the BACK of the knob, when you turn the knob to thr right to increase from fan speed 1 to 4, in this image our contacts will be turning to thr left...

    Fan speed 1 the contacts touch 1, B, H
    Fan speed 2 the contacts touch 2, A, G
    Fan speed 3 the contacts touch D, 3, F
    Fan speed 4 the contacts touch C, 4, E

    What I wanted to do is to create a position 0 by carving out the "stops" in the white plastic peice and the black plastic piece. I wanted the zero position to coincide with the "fan" icon that is to the left of the "1" position.

    But as you can see, if you were to start at fan speed 1 and rotate the switch to the left (which since in the image we are looking at the BACK of the knob, we then look that the contacts rotate to the right) you would have the contacts touching:

    Proposed fan speed 0:
    contacts touch E, C, 4.

    Which means that a position zero would actually run the fan at fan speed 4. This wouldn't work.

    However - since at any point in time, two contacts are touching ground, you can remove one contact and still have functionality. The three probably are only there to balance out the pressure, so that there is equal pressure on all the contacts. So you can't actually remove one of the knob contacts, but you can cover it up with tape - so that it never makes contact.

    The knob contact that is relavant would be the one that would rotate at the bottom of our picture, in the positions H, H, F, and E.

    By covering up that contact with electrical tape, it insulates it while still keeping the balance of the three contacts on the disk... We used 2 layers of the thick 3M stuff with good adhesive, and wrapped it around the contact so it would stay well. If you see the above posts - this should last a while.

    Then, using a dremel tool and exacto knife, we carved out the knob "stops" that are in the black piece of plastic, and carved the stop and some corrosponding new "dimples" in the white plastic. (You will easily see what I mean if you are looking at the pieces). This way the fan speed knob can rotate one "click" to the left of the 1, pointing to the fan icon. That setting is "FAN OFF", or fan speed "ZERO" and will allow vented airflow, while keeping all four of the factory fan speeds.

    And remember, do not use fan speed zero with the A/C or Defrost on. (And this includes the floor position unless you modify that too). With the AC on you need good airflow or you can damage the AC.
     
  18. valkraider

    valkraider New Member

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    We ended up marking where the contact occurs using a dab of wet paint, and then we dremeled out a divet a bit bigger than that spot, and filled the divet with non-conductive modeling type cement, then sanded it down to be smooth and even with the copper. We never cut through the copper so it is all still there and conductive - just not making contact there at the "floor" position. Just the same effect as tape I guess, just more permanant.

    I decided I was not so much concerned about the wearing of the tape, as people's tests showed that would take a while. And the grease keeps it lubricated pretty good too.

    I decided the bigger risk was for the adhesive to fail or the tape to move... Due to heat or anything like that... So we just made it more permanant.

    All in all, the heater control is not too hard to get out and apart. Since it is not extremely easy to know when the AC kicks in I wanted this fix to be permanant. If there are problems with the tape in my other fan speed modification - I will know as my fan speed zero will turn on the fan speed 4. Obvious if it happens.

    :)

    All in all, THANKS for all the help! This is freaking awesome. Just fixed my biggest gripe with my Liberty in a couple hours with a friend and a dremel tool.

    :)
     
  19. omniphil

    omniphil New Member

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    Your dedication to detail is impressive. Nice work.
     
  20. roadrunner

    roadrunner Full Access Member

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    Great solutions to a poor engineering job!=D>