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Mercury Mariner 2008 --Heater/air conditioner air flow control

Posted by arleneb (My Page) on
Sat, Aug 24, 13 at 17:31

Mercury Mariner 2008 --Heater/air conditioner air flow control switch works only on high speed. Fuses and relays listed in manual l checked are both ok . (I checked blower relay, which is 21 c and the blower motor fuse at location 45.)

Any suggestions?


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RE: Mercury Mariner 2008 --Heater/air conditioner air flow contro

By air flow control swotch, are you perchance refering to the speed control for the blower? If so, you probably have a burned out speed control resistor. The blower speed is controlled by inserting resistance in series with the motor. The speed control shorts out parts of the resistor progressively in steps and at maximum speed, the entire resistor is shorted (bypassed).

By your description, the motor is good, there is electric power avalable to the heater motor circuit, therefore, fuses/breakers in the circuit are good.

You'll need to consult a repair manual to locate the resistor assembly. Often, these are mounted on the air flow duct with the resistors in the air flow. The resistors are cooled by the induced air flow. If you are lucky, it is accessible from under the hood, but if unlucky, it'll be under the dash.


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RE: Mercury Mariner 2008 --Heater/air conditioner air flow contro

Thanks for your reply-- was able to talk to a mechanic this morning and afraid we are one of the unlucky ones--he said it is in the dash.(a little beyond hubby's auto mechanic abilities). We left it at the shop a little while ago. Thanks again for your help.


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