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2000 Mercury Villager Question: Front AC/Heater Fan speed resistor keeps failing every 8-9 months.

 

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USMA82, 3.3L V6, Hamden, CT, August 04, 2012, 11:29
 Enthusiast

The fan speed resistor for my front A/C - Heater keeps failing. Part only seems to last about 8-9 months before it burns out (then only high speed works). Any ideas why?

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  • Answer #1

    ziptie12 August 04, 2012, 22:34
     Master

    Get specs and test other parts in the circuit for improper resistance. Possibly blower motor pulling to much current.

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    pushrod, August 05, 2012, 01:06
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     Master

    Agree with 1 resistance is also a bad connection anywhere in the circuit.
    Check connector's for signs of high heat ie melted conn.plastic,blackened
    metal terminals. Repair connector kit avail.

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    USMA82, August 05, 2012, 07:57
     Enthusiast

    Thanks all!
    Good advice, although where can I find the specs for the Fan blower motor circuit?
    My repair manual only provides a wiring diagram and fuse rating.

    BTW, I did check wiring for evidence of over heating. All looks OK, but the failed resistor boards do show signs of overheating (excessive current draw?).

    Would a low voltage condition cause the problem?
    My alternator is orignal (156K miles), but I do not have a starting problem or low battery issue.

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    ziptie12, August 05, 2012, 10:00
     Master

    Check all grounds carefully & if in doubt clean/repair as necessary.Are you using an ohmmeter or just visual inspection?

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    USMA82, August 05, 2012, 14:37
     Enthusiast

    I have an ohm meter, but i do not know what resistance is acceptable.

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    USMA82, August 05, 2012, 14:37
     Enthusiast

    I have an ohm meter, but i do not know what resistance is acceptable.

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    ziptie12, August 06, 2012, 20:13
     Master

    For any ground circuit -as close to zero as possible. Also just thought of something else-- is there any damage to the heater box that would restrict or block airflow past the resistor?

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    USMA82, August 07, 2012, 09:38
     Enthusiast

    No damage or blockage that I can see. I'll check the wiring when I replace the resistor board. Thanks for your help!

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