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  • Pat in Ma
    replied
    I'll add my .02 to this problem and suggest that since it's hidden on the lower part of the housing you could replace it with a newer
    modern resistor stack from a current Ford product and only connect the wires to the resistor that is close to the value of the original.
    Of course if your looking for originality then this is a bad plan. Again, just my ,02 which is worth exactly that.

    Best of luck.

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  • simplyconnected
    replied
    Ray, there are a few ways to skin this cat. The easiest and quickest way would be to replace the resistor. Of course, that may not be the cheapest solution but check this out:
    https://www.rearcounter.com/C1SZ-185...rts183404.html
    These are the places around the country that say they have your resistor.
    • I called Dennis Carpenter but he can't price his NOS part until Monday or so.
    • Another option is to replace the motor with a 3-wire. I would guess they cost around $30.
    • The third option is to buy and mount your own resistors as I described earlier. eBay sells them.
      This option may not look the best but it's probably the cheapest solution. - Dave

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  • Ratboy
    replied
    I will check the connections when I get home today. I did put dielectric paste on the connections but maybe I didn't get it put back on correctly, it's a blind fit. If it is a bad resistor what do I use to replace it

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  • simplyconnected
    replied
    That's right. With the key on and the heater switch turned to 'low' you should measure voltage on BOTH sides of the resistor (to ground). One side will show +12. The motor side will show zero if the resistor is open or a lower voltage if the resistor is good. Be careful here, I have seen plugs that were bad (but the resistor was good). I pull the plug off and look inside to check for corrosion or melted plastic, etc. Measure the resistor with the plug disconnected using your resistance scale on your meter. - Dave

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  • Ratboy
    replied
    I finally have daylight time to check the resistor, the coils look fine. But there is 12v on one end (testing underneath where the 2 wires connect to the resistor) and nothing testing the other connector on the resistor. So apparently my resistor is bad. Should I put the new resistor in the heater plenum again? Is there a special resistor that I'm looking for? Thought someone mentioned Ebay but it must be on a different posting
    "If the resistor is bad, or open, you should measure +12 volts on the power side, ZERO volts on the load side and the resistor will be cool."

    My bird has a control panel light- illuminates the controls under the radio. Fig 23

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  • simplyconnected
    replied
    Originally posted by Ratboy View Post
    Thanks, I see that now. One of the easier wiring schematics I've found. If the resistor is bad, where is it located? I tested the low speed wire and it showed it was a complete circuit...
    I'm showing both the older three-wire and the two-wire motor circuits:

    1958-1960-blower-motor-circ.gif
    I'm not real happy with their layout, but the major components are there. FIG 12 says the power comes from a 'fuse panel' that doesn't exist. In fact, the fuse is an 'inline fuse holder' right next to the fan selector switch that is fed from the 'A'ccessory post of the key switch.

    In FIG 23, the resistor should show that it is in an enclosure with dotted lines around it, on the engine side of the firewall.
    BTW, what's that 'control panel light' doing there in FIG 23?

    Here's another A/C diagram for a three-wire heater motor (which is why there is no speed resistor):

    A-C_HeaterBlowerMotor-Circ.jpg

    This is interesting because I'm not sure where the '20 amp circuit breaker' is, or why Ford didn't simply use the same fuse. Remember, over-current devices are there to protect the WIRE, not the motor, the resistors or the clutch. - Dave

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  • simplyconnected
    replied
    The resistor is a very simple ni-chrome (resistance) wire, coiled to shrink the length. Yes, it gets hot.
    nukem25rs is right about 'air flow' that cools the resistor, otherwise it would overheat and burn open. (This is very common, even with modern resistors.)
    What happens if you cannot find an OEM resistor? Any resistor may be used if it safely dissipates the WATTS. (Volts times amps = watts.) Normally, we determine the current needed for the desired motor speed, then we multiply that current by 13 volts to give us the watts. For example if the motor draws 3 amps we get 13x3 or ~40 watts. What's the resistance? (volts divided by current = resistance or 13 divided by 3 = ~4 ohms.) So the resistor is about 4 ohms at about 40 watts. To keep the heat down we DOUBLE the watt capacity of the resistor. Another way is to connect two (8 ohm, 50 watt) resistors in parallel. Why? Because eBay sells them cheap and they can mount anywhere.


    fetch?photoid=238336&type=thumb.jpg
    p38fighter shows the resistor after removal.

    fetch?photoid=238339&type=thumb.jpg
    YellowRose shows the resistor 'in place' from inside the blower housing.

    The schematics 'kind of' shows the resistor close to the blower motor as jopizz indicates but it isn't too specific. If you follow the wires from the motor you will find the resistor is very close.
    Two-wire or three-wire motor, does it matter? Not at all since the resistor turns a two-wire motor into a three-wire motor. Both motor speeds work exactly the same. If you have the three-wire motor, good, simply connect the orange and red wires. All of the old Fords had three-wire blower motors including six volt systems.
    As you can see from this example, a two-wire motor may become a two speed by adding a simple resistor. Modern cars take this same principle using a two-wire motor and adding more resistors to make more speeds (5-speeds are common). Modern resistors are normally inside the firewall, screwed into the heater duct (plenum) with a plug. - Dave

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  • nukem25rs
    replied
    well another thing cool with that resistor.... they probably put it inside the blower so the blower would cool the resistor as it worked!

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  • Dan Leavens
    replied
    Gentlemen: I am amazed and blown away at the technical knowledge of our members and the exchange of threads on this issue. That is why I always say, that this is the best TBird site on the planet

    Leave a comment:


  • YellowRose
    replied
    Here is a picture that I took when we were troubleshooting the Blower Motor years ago... Tweety had OEM AC also... You can see that resistor in this picture...

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  • Ratboy
    replied
    that looks like what it should be according to the schematic in the repair manual. is it difficult to remove the housing? I haven't gotten that far yet

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  • p38fighter
    replied
    John, Is this what he's looking for? It was mounted on the bottom of the blower motor chamber.

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  • jopizz
    replied
    Originally posted by Ratboy View Post
    Is this the resistor? It disintegrated on me.
    No. That's the thermostatic switch for the compressor clutch. The resistor is in the wiring harness between the blower switch and the motor.

    John

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  • Ratboy
    replied
    Wow, that's some great ideas. Thank you.Apparantly, I have a 2 wire motor although Bird Nest said AC is 3 wire and mine has factory AC. Is this the resistor? It disintegrated on me.
    IMG_20191107_080529.jpgIMG_20191106_160157.jpg

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  • simplyconnected
    replied
    Whenever I troubleshoot electrical circuits (except shorts), I always start at the END, and work towards the power source. In your case, the end is your motor.

    Is your motor a 2-wire or a 3-wire? The motor in the drawing is a 2-wire (power and ground). The orange wire supplies full +12. The red wire limits the current through a resistor, then they splice it to the orange motor wire. The resistor location should be close to the motor, not the switch because it may become very warm or hot.

    Three-wire motors have separate field windings for different speeds and NO resistor. Older Ford blower motors (and power window motors) use them but troubleshooting is similar. These are not permanent magnet motors. They have an armature and field(s) that are connected inside the motor. Reversing the polarity will not change direction of the motor unless it has magnets inside. If you're game, go ahead and try it.

    Let's begin troubleshooting... Put your meter on VOLTS. Connect one prod to a good ground.
    With the dash switch on LOW speed and the key on, test the orange motor lead. Normally, the motor should be turning with these settings.
    If you have +12, that's great.
    If you have some low voltage, like 5 or 6, find the resistor by following the wire towards the firewall. Check voltage on BOTH sides of the resistor. One end is the power side and the other end is the load side. Is the resistor hot to the touch? If so, the motor may be too hard to turn or the brushes inside are gummy.
    If the resistor is bad, or open, you should measure +12 volts on the power side, ZERO volts on the load side and the resistor will be cool.

    Sometimes I like using a light for testing voltage. It can be made from a dash light (#57) with two long-ish leads. The bulb IS a load that will shine different brightness for different resistances. In other words, you can see a very bright +12 volts and a much dimmer 6 volts. This 'tester' can be made with a simple length of speaker wire soldered to the bulb. The cost is nothing. You can get fancy and include alligator clips but in this case, I would tin both ends and put the ground end under a bolt. I also use this wire for finding wires shorted to ground. How? Pull the blown fuse and replace it with both leads wrapped around a small wooden stick. The final diameter should be 1/4" and the length should match the fuse length. A grounded wire will make your bulb shine. Start pulling bullet connectors in that circuit. When the light goes out, you're on the right path. I've followed wires all the way to a license plate light socket that was corroded. - Dave

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