4WD Troubles - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 3 (permalink) Old 11-20-2009, 02:33 AM Thread Starter
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4WD Troubles

My auto hubs won't engage unless i lock them manually. Checking for vacuum leaks today and found the hub vacuum switch is not switching. Can anyone tell me which wire is witch and what the voltages should be going to this switch?? I checked them and i got 12 volts going there but nothing seems to change when i switch it to 4x4. Thanks Jerry


2002 Ford F-250 Crew Cab 4x4, 7.3L P stroke, Auto. Superchips programmer.
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post #2 of 3 (permalink) Old 11-21-2009, 02:04 AM
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I assume you have a good vacuum supply to the hub/lockout solenoid. the most common problem is the vacuum pump here. The other 2 wires to that solenoid go to the 4wd for module. the module grounds these 2 circuits to activate the solenoid to provide vacuum to the hubs, keep in mind the vacuum to the hubs are pulsed and once engaged the vac supply is cancled because the hubs will maintain engagement/disengagement on their own.

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post #3 of 3 (permalink) Old 11-21-2009, 08:30 AM Thread Starter
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Thanks 4play,
I do have vacuum to the switch. Pump is good. I checked the switch and it does seem to be grounding the 2 wires when i go to 4x4 but no vacuum is coming out of switch. I am going to get a new switch..


2002 Ford F-250 Crew Cab 4x4, 7.3L P stroke, Auto. Superchips programmer.
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