View single post by Mark Rosenbaum
 Posted: 09-08-2006 11:44 pm
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Mark Rosenbaum



Joined: 03-12-2005
Location: Kingman, Arizona USA
Posts: 532
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 Due to the federally mandated Infamous Seat Belt Warning Module (ISBWM), a JH may fail to crank for any number of reasons.  The ignition switch, when activated, applies power to the ISBWM.  If, and only if, (a) the parking brake is activated, and (b) the seat belt for each occupied seat has been buckled, will the ISBWM allow the start relay to be energized.  This relay, in turn, applies power to the starter solenoid.  The starter solenoid applies power to the starter motor, which cranks the engine.  A failure anywhere in the chain will prevent the engine from cranking unless manual intervention of the sort you describe, takes place. 

The (inexpensive, available) relay is present so that the electrical load on the (expensive, rare) starter switch is reduced to a sensible level.  Consequently, it is rare for a JH ignition switch to fail if the car's electrical system is stock or nearly so.  The relay and ISBWM may fail more often.

Often, an owner will defeat the ISBWM, or avoid the need for replacing a defective one, by jumpering pins 11 and 12 on the round wiring connector that plugs into it.  This permits the ignition switch to energize the start relay directly.  This also allows the Fasten Belts and Key In Ignition And Driver's Door Open warning functions to operate normally (assuming they still work, of course).  More extensive alterations, such removing the entire ISBWM system and associated switches and wiring entirely, would disable the two warning functions.

The relay, ISBWM, and turn and hazard flashers, are all located on the driver's side kickpanel forward of the dash.

Last edited on 09-08-2006 11:45 pm by Mark Rosenbaum