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Old 01-31-2011, 08:45 PM   #1
Farm Bus
 
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Default Heater fan high speed not working

Position 4 (fastest) quit working on the heater blower. I have located the resistor block, and have read that position 4 is "no resistance". I can check other positions by checking resistance across the different positions on the block. But if 4 is "open" with no resistance, how do I test what's bad?

What would cause the fastest speed to cut out? By the way, when the fan is in position 4, it is running at speed 3. I can click between 3 and 4 with no change in speed. I know it's not 4 because 4 is really LOUD.

Really what I'm asking is how to I keep from being sold a repair that I don't need? "Oh ya, you need a new blower and resistor block and tranny"

Brian
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Old 01-31-2011, 10:05 PM   #2
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Default Re: Heater fan high speed not working

Did you mean "no resistance" or "no continuity"???
"No resistance" would be shorted which is what position 4 is supposed to be. If 3 & 4 are both the same I would suspect a problem with the switch. Here's a wiring diagram from the manual.
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Old 01-31-2011, 11:40 PM   #3
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Default Re: Heater fan high speed not working

Oops, ya, well fortunately I didn't actually DO it . . . This from the 05 manual:

(3) Check for continuity between each of the
blower motor switch input terminals of the resistor
and the resistor output terminal. In each case there
should be continuity. If OK, repair the wire harness
circuits between the blower motor switch and the
blower motor resistor or blower motor as required. If
not OK, replace the faulty blower motor resistor.

So you're right, I would have been checking continuity. Regardless, with 3 and 4 being the same, you'd bet on the switch?

I appreciate the wiring diagram, only it's beyond my abilities to decipher.

What would be a way to confirm that it is the switch? Or is that the only candidate if it is not the resistor block given the symptoms?

Thanks again
Brian
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Old 01-31-2011, 11:46 PM   #4
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Default Re: Heater fan high speed not working

Oh crap oh crap oh crap. Does this mean I have to replace the entire module, not just the fan switch. Seriously?

DIAGNOSIS AND TESTING - BLOWER MOTOR
SWITCH
The blower motor switch can be diagnosed by using
the DRBIIIt scan tool. Refer to Body Diagnostic Procedures.
For circuit descriptions and diagrams, refer
to the appropriate wiring information.

The blower motor switch cannot be adjusted or
repaired, and if faulty or damaged, the heater-A/C
control must be replaced (Refer to 24 - HEATING &
AIR CONDITIONING/CONTROLS/A/C HEATER
CONTROL - REMOVAL).

Tell me please that I can just replace the switch! Anyone done it?

Brian
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Old 02-24-2011, 11:28 AM   #5
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Default Re: Heater fan high speed not working

Hi.
Did you resolve proplem? My sprinter 2004 is same proplem.... heater 1.2.3. speed are ok, but 4. is same as 3.
Where locate this "Auto Temp control(ATC)"?

Many thanks
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