getting rid of the pcm ?'s

[therabbittree]

Ok I have two trucks my '89 W350 727 as a parts truck and my "new" '92 W350 5spd. the '89 has a mechanical cable driven speedo, external voltage regulator, and no PCM etc etc. The '92 has a pcm and the volt gauge dips up and down pretty often. . I don't like that. that truck also has had to be put on the battery charger a few times to start it . . argh. . I think the pcm is bugging out. what do I need to do to get rid of the PCM totally and make it like my '89???

Has any one done it here? I have heard of people swapping parts of it out . . etc. . but since I have the '89 right next to it . I am ready to swap over what needs to be swapped ... give me some input and ideas.

Thanks,

Deo

 

[Moab4x4]

PCM controls Alternator field, Air conditioning clutch relay, cruise control (if ya got it), cold start intake grids, check engine light, wait for start light (associated with the heating grids), water in fuel light.

I would replace the whole engine wiring harness with all related modules and relays that are attached to it.

I am curious if the electric speedo will work without the PCM. From my digging deeper into the schematics, I think it will. It looks like the speedo head powers the VSS. If the speedo head is on the way out, you can provide an external power source for a little while and then it will quit again.

Mechanical head and gear is pretty tough and hard to beat IMO.



If the battery charging is your only issue, you can tap into the harness and wire in an old school Mopar voltage regulator. That would be a lot less work. Wire it like the old truck. you can scavenge the plug off any old mopar or get a new one from carquest. I have seen a few trucks with that as the only mod with the PCM still in.

When I did mine, I looked in my 70's motor manual charging schematic and did it that way and it worked.

 

[dpuckett]

My nonIc 91 had the electronic speedo, and voltage regulator on the fenderwell (at least after heat ate 3 in a row- I moved it)



If charging is your only issue, I'd do like Moab4x4- bypass the PCM for the volt regualtor. I had it done on my last 93 in 2002. WOrked real well. Had to take out the bulb on the "check engine" light.



Daniel