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Thread: How-to: Permanently fix the "no A/C on fan speed 2/3" problem

  1. #61
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    Quote Originally Posted by pcb View Post
    OK,.. I read your analysis and it makes complete sense. (I am reasonably proficient with electronics) However my main concern is still the same. If the internal resistance of the switch (which is where I believe most of the resistance is coming from followed by the connector at the back of it) is enough to produce a 1.1 volt drop, that is 1.1 V x 6.35 amps equals 6.985 watts of heat in the switch for fan speed 2. For fan speed three, 1.1 V x 8.8 amps is 9.68 watts of heat and 1.1 V x 11.75 amps is 12.925 watts for fan speed four.
    That is plenty enough heat to start melting things.

    http://www.mazdas247.com/forum/showt...32#post6121332

    If you crank up the cutoff voltage to 3 v then the heat in watts goes to 19.05 W, 26.4 W, and 35.25 W before the light would start to flicker. That's enough to cook a burrito on the fan switch. (consider how hot a 25 watt brake light bulb gets)

    My AC light started to flicker last summer for the first time. I took apart my switch, cleaned and sanded the contacts and all the pins and connectors on the connector plug. That fixed everything and I got to it before the big meltdown. I kinda like the fact that the light flickers at 1.1 volts because it gives me enough warning to clean the switch and contacts again before everything liquefies.
    I also noticed that the connector plate inside the switch is kinda spring loaded so I stretched the springs a bit and bent things a bit to help provide more pressure on the contact. I also put a bit of white grease in it.

    Let me know if my math is right ,... I know that not all the resistance is in the switch, some is at other connections and some in the wire itself.
    I see what you're saying, the flickering A/C light represents a more serious problem. I'd argue that for most people this isn't dangerous, of course if you notice that your switch connector is a bit melty then you should probably address that problem first. We're not trying to bypass an intentional safety system here, we're trying to fix some sloppy engineering.


    I don't believe the internal resistance of the switch has much to do with this problem. The resistance comes from corrosion on the connector contacts. Keep in mind that in order to get a 1.1V @ 8.8 amps, all you need is 0.125 Ohms of resistance. That's pretty easy to achieve if you assume that both ends of the ground wire have some corrosion and that you'll have ~25 mOhms across the switch. Your pictures would suggest the same thing, the inside of the switch still looks pretty good but the connector contacts are completely tarnished. Thus all of the power that is being dissipated will be along the ground wire, with the bulk of it being dissipated at the two ends of the wire. It would be interesting to throw one of those fancy bonding testers on the ground terminal to see just how bad it really is...

  2. #62
    The Diagram Dude pcb's Avatar

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    When I cleaned my switch, the worst of it was inside the switch itself. The connector terminals needed some sanding to make them shiny again but that flimsy ass rotating piece inside the switch was a joke. All those amps are going through a tiny 2 mm (or less) contact point covered in black goop (old dirty grease) and the contact point was all tarnished when I wiped off the old grease. I think all the problems start from there. The fact that it rotates to make the different connections spreads a thin film of grease (resistance) on the contact mixed with rubbing and maybe some arcing starts the whole resistance and heat process which radiates to the connector pins where everything snowballs.

    I don't know if you've had your switch apart at all but I think you should just to have a laugh at what I think is the best example of shitty engineering on this car. Even the headlights have relays because of their current demands (55 watts / 12 volts equals 4.58 amps) almost a third of what is running through that switch at fan speed 4.

    I would suggest if you take apart your switch to open it over or inside a bucket to catch all the flying parts when it opens up. There is a spring and ball bearing on the back-side which allow the selector to "click" into the dedents for the different fan speeds. It helps to put a dab of grease on the ball bearing during re-assembly to keep it from falling out.

    There is a plastic lock-nut on the switch that holds the whole thing in place when everything is installed. The nut is all cheap-ass too and will probably break as mine did. I ended up gluing the switch in with a glue gun so I can remove it again when it comes time to doing another switch cleaning.

    P.S. What's a bonding tester?? I assume it measures small resistances across contacts and wires in high current circuits.

    P.S.S. I'm pretty sure that the semi-transparent plastic of the connector melts at a much lower temperature than the white plastic inside the switch, so that would be the first part to melt. (thermo-plastic vs. thermo-setting plastic maybe?)

    I don't think coating the refurbished connector with glue gun is a good idea (like the guys in the other thread are doing), it melts way too easy and holds the heat in not allowing it to "breathe" and even if any of those wires in the connector "short" to ground (from being bare and open) it doesn't blow any fuse,... it just completes the ground circuit and the fan will turn on. I would leave it open and bare to help cool it down.
    Last edited by pcb; 03-27-2013 at 09:32 AM.

  3. #63
    Registered Member randomations's Avatar


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    Quote Originally Posted by CheeseHelmet View Post
    You're half-way there :P

    It sounds like you didn't connect the input (the white wire in my pictures). Please re-check your connections.
    Thanks. I'll look at it again in a couple days when I have some time. I used wire nuts for the connection, and maybe that blue/yellow wire slipped out. From your pictures I was expecting it to be a higher gauge than it was.

    Thankfully we've got a longer cool season this year in Orlando so I've got some time to get it right.

  4. #64
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    Question- What gauge wire should we be using when hooking up those wires? Would 12 AWG be alright?
    Last edited by kosteniuks17; 03-27-2013 at 02:55 PM.

  5. #65
    Registered Member randomations's Avatar


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    Quote Originally Posted by CheeseHelmet View Post
    You're half-way there :P

    It sounds like you didn't connect the input (the white wire in my pictures). Please re-check your connections.
    It's definitely connected just as your picture shows. Maybe I'll go ahead and put my extra set of materials together and see what's up.

    Just to note. I wrapped both ends of the "pigtail" this creates in electrical tape, then wrapped the wrapped ends together to keep things isolated.

  6. #66
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    Quote Originally Posted by kosteniuks17 View Post
    Question- What gauge wire should we be using when hooking up those wires? Would 12 AWG be alright?
    There's such a small amount of current passing through those wires that you can use almost anything. 12 AWG would be overkill.

    Quote Originally Posted by randomations View Post
    It's definitely connected just as your picture shows. Maybe I'll go ahead and put my extra set of materials together and see what's up.

    Just to note. I wrapped both ends of the "pigtail" this creates in electrical tape, then wrapped the wrapped ends together to keep things isolated.
    That's odd, if you have some pics of your installation please post them.

    If you have a multimeter, measure the voltage at the junction between the two resistors with the fan off. It should be 12V.

  7. #67
    Registered Member rit14623's Avatar

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    Quote Originally Posted by pcb View Post
    ...There is only one true fix for this issue and I love it:
    Now these switches are rated for a good 15 amps:

    Ha ha. That looks ghetto. I mean why stop at the fan switch? Just replace your entire center stack with columns and rows of these wall-mount switches.

  8. #68
    The Diagram Dude pcb's Avatar

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    ^yea I love that ghetto approach,... those switches will last 30 years longer than the car will.

  9. #69
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    Quote Originally Posted by pcb View Post
    ^yea I love that ghetto approach,... those switches will last 30 years longer than the car will.
    I actually saw a cadillac at the junkyard today with one of those switches in place of the ignition switch, classy as fuck :P

  10. #70
    Josh


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    Hey CheeseHelmet you mind to fix the link to your analysis link? I really want to read it lol

  11. #71
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    Quote Originally Posted by maxchao View Post
    Hey CheeseHelmet you mind to fix the link to your analysis link? I really want to read it lol
    Sorry about that, it's back up. I'm in the middle of upgrading the OS on my server so some stuff might be a bit wonky on the site...

  12. #72
    Asian Persuasion <>< Hank3's Avatar
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    Did this mod a couple weekends ago. No more flickering on fan speeds 2/3. The butt connectorsI got from Radio Shack didn't work...didn't make good contact. Winded up splicing the wires and used heat shrink and electrical to secure everything. This will be the first summer without ghetto a/c. Thanks!
    Last edited by Hank3; 05-13-2013 at 11:30 PM.



  13. #73
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    Quote Originally Posted by CheeseHelmet View Post
    Sorry about that, it's back up. I'm in the middle of upgrading the OS on my server so some stuff might be a bit wonky on the site...
    Very impressive...I don't know how you reverse-engineer all those detail but it is nice to see...I finally know how this thing works. (and the fix)

    So the most annoying about the car is fixed....a decade since the car came out.

    Thanks CheeseHelmet

  14. #74
    Josh


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    I just got it done...I am about to burst into tears! Oh fan speed 3 is really the best for the AC...it feels so good...after all these years...

    So I went to radio shack and they only had 220 ohm resistors no 200 ohm resistors. They also sell 5 resistors at minimum, so I picked up only 5 220 ohm resistors and put two in series to replace the 470 ohm resistors. It still works. Saved me $1.50. :P

  15. #75
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    Dude I just installed the circuit into my AC wire bundle, and guess what it FREAKIN WORKS!! after all these years all it took was a half day for supplies and installation. Its really simple, just follow instructions and make sure that you make good contacts. Also the ground snap connects are a pain in the ass to get them to hold the small 18 guage wires. I eventually got mine to hold, you just need to make sure the small wires are shoved all the way in there. If anyone is thinking about doing it, JUST DO IT! It's kind of fun and now it doesnt flicker at all, like speed 2 completely didnt working and 3 was on and off. Also it would flicker when changing the fan speeds. But it solved it completely, no flickering at all. Might be a little hard to install the radio back in cause that wire is right behind it, you just have to force it down and you should be good. Also make sure you use good crimps because those wires are really small. Good Luck!

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