Been trying to come up with a simple wiring schymatic for the O/D on my A-518 that bypasses the PCM and is easy to install, and I think I've about got it. After lots of thread chasing and pings to several folks, and after a real good conversation with Alan ("cerberusiam"), I think I've got it - So here's the plan:
Three switches - the O/D 2-prong, a hobbs pressure switch, and a kill switch. 12v power to the O/D, ground coming out going to one side of the hobbs, the other end going to the kill, the other end of which goes to ground. All connected and 'enabled'...at the specified pressure/speed...the circuit will ground/close thus engaging the O/D. But, flip the kill switch (on-off switch in the cab) and that opens the circuit, disabling the O/D. It couldn't be any simpler, and it completely bypasses the TPS, the PCM, the XYZ, the R2D2
and -
and the C3PO....and all the other maddening factory problem areas there are in a 1st gen wiring harness
.
Now, doing it this way
guarantees that the O/D
will engage regardless of load, temperature, throttle, time of day, day of the week, weeks in a year or alignment of the friggin' planets. So, the driver will need to be gentle on the O/D during warm-up and under big loads......and I'm that way anyway so no problem. But it also guarantees that the O/D will not
disengage when it's
not supposed to...ever...and that is
good. If any of you have driven a 1st gen with an auto you know how all-of-a-sudden infurating the O/D can be #@$%! - well this bypass should be the hot ticket, and it'll be easy....and cheap
And hey Chipster - thanks mucho for the hobbs switch tip amigo - that's about as slick as it gets!
Stand by for the full wiring diagram and testing.
- Sam
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ASA Modifieds
www.asamodifieds.com
'93 D250 Club/LE auto/3.54's, PDR HX-35/14(gated), PDR pin, ASA Intake & 4" Downpipe, PODs, ATS manifold, fuel max'd, 366 spring - dyno'd 308/620, DTT converter, MagHytec pan/diff cover, Autometer x6, column o/d...
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