High Idle aborts??
Background on the vehicle: at my volunteer fire house we have a 2013 F450 Chassis cab based ambulance. When the temps drop into the 30s or below (fairly common here in Maryland), and the truck idles for more than 5 minutes (being on scene of a call), the cabin starts losing some heat (the patient compartment keeps pumping heat though). This can be completely remedied by revving the truck up to ~1200rpm, and within seconds heat is strongly flowing back into the cab.
Additional long story short, the spec writers for our build forgot a number of things, one of which was a high-idle switch. Subsequently, I followed the wiring instructions found here (and elsewhere) and wired a resistor inline and wired Upfitter #4 to activate the high idle.
The operation of it is not correct though. Assuming everything is up to temp, if I activate the parking brake (in park), and turn on Upfitter #4, it will raise the idle to ~1300, hold it there for 2-3 seconds, and then drop back down to normal idle. Almost as though something in the "requirements" for high idle dropping out (like hitting the brakes or moving the shifter when it's doing a manual regen).
Any ideas on this? Is there another way I can trouble shoot this?
Thanks!
https://www.fleet.ford.com/truckbbas/non-html/Q-244.pdf
Try emailing the Body Builders at Ford and see if they can give you an answer.
bbasqa@ford.com
I will say if I turn it too far up it kicks off high idle kinda like yours does. Maybe u have the wrong ohm resistor.







