Destroking wiring question... 12V in an F350

O

OnVacation

New member
Joined
Apr 26, 2011
Messages
381
Well, the PO had a cool engine built, sorta. wiring was a bit, well... unique.

so, I'm going through removing the old wiring for the V10 and for the tranny, cleaning up the wiring for the grid heaters, integrating things to work off the switch instead of buttons, etc.

Realized, a lot of the useless wires head back to the PCM.

I know some of the sensors run back through the PCM. Can I direct wire these to the wires heading up to the gauge cluster and totally remove the PCM and finish cleaning up my engine compartment? I've already had one electrical engine fire from wires shorting out, I don't want to do it again...

Would I lose anything by totally removing the ECM?
 
roachie said:
It has to have the PCM. You cannot bypass it.
Click to expand...

Well, I know the truck will drive down the road with no electronics at all just fine, so it can be bypassed (its a 12 V and stick shift, it only NEEDS the shutoff solenoid wired open). What does the PCM control? does it simply modify the signal from the gauge senders to something the cluster can understand? does it link in with the cruise module? I know it doesn't have anything to do with the lights, radio, etc. I'm not doubting you, I just want to know the costs so I can make educated decisions.
 
Gauges, alternator, on board diagnostics, A/C, cruise........all these need the PCM. The GEM module under the dash controls the lights, windows, and restraints. If you delete the PCM, you will need to completely rewire the truck to keep all that functioning. At that point you will be 100x more likely to have a fire from wiring.
 
so when you did your swap, did you just splice in to what was there, or remove the unused wires?

Most of the truck has stand alone sections. the alternator is wired into the voltage regulator (there is a thread on the process somewhere), its got some other kind of cruise control module wired in (not sure if its a cummins piece, or off of some other superduty, but its not in a standard mounting location), the OBD is already killed (light was removed) and the AC is currently disconnected (another project for another day) I don't want to create work for myself, but I've had one engine fire, twice unable to diagnose a circuit due to strange wiring, and once stranded without headlights (relay was loose, and relocated underneath the battery tray...).

I'm comfortable with my soldering iron and shrink tube. I just want the engine compartment clean, to have the cummins look like it belongs there, instead of like an afterthought.

I want an engine bay I don't have to make excuses for any more
 
I'm really not trying to be combative. Army mentality has me to the point where I like to fully understand the costs and benefits of all my different options and assess the problems before I make a decision and start moving forward. I can see from your sig you know what I'm going through, figured I'd get all the information from you I possibly could...
 
Both of mine are spliced into the OE wire looms. The 04 has a 24v so I laid the ford sensor wires in the cummins harness. I only have 2 wires that do not use OEM connections, they are both run directly to the ignition switch. The 99 is a 12v and I made an engine harness, it splices into the body harness that runs to the PCM using a 5pin connector. On both I deleted any wire I didnt need.


If I was in your shoes, I would take the truck apart on the front rip out ever single bit of wiring that isnt factory. Go back and redo it properly. The cruise may be a ford unit, they have to be relocated to reach the throttle.


This is my complete engine harness on the 12v

222620_10150250655455850_777585849_8857079_2701940_n.jpg

230349_10150250657575850_777585849_8857116_7671302_n.jpg
 
I'm slowly pulling the wires, and splicing them in correctly where needed. I think I'm gonna have to follow in your shoes to have it done right.
 
question straight back at you, on the '99, how did you wire the starter? I know the '99 actually grounded a circuit for the relay to start, but I can't seem to figure out which wire it is. PO had it wired up to a push button, and I want a more benign turn-key ignition...

And, similarly, I've got the diagrams for the AC, but I'm really kind of lost on that, as far as the wiring goes, is there a trick to it?
 
Last edited:
Depends on what engine/trans your truck had to start with. I have a wire running from the oe solenoid on the right firewall, through the engine harness and back down to the starter and fuel shut down.

If you done it like that you will have to trick the PCM into thinking it is in neutral. That was simple as hell for me.
 
The white wire is the neutral wire, I just looped it back to the connector. If you want too, you can follow the harness under the fuse box and rig in a clutch safety switch. The other is the reverse lamp switch on the trans.

227879_10150250656130850_777585849_8857091_6194584_n.jpg


227295_10150250656085850_777585849_8857090_3710455_n.jpg
 
Okay, between your posts and a new subscription to alldatadiy I've gotten most of the critical wiring fixed (Why the hell did they cut the ABS sensor wires?!?!)...

regardless, I ran the stub wire for the AC back over to the passenger side. I know factory had a pressure sensor on the expansion tank, then a switch on the compressor. my compressor for the cummins has three wires on it. Whats the deal here? I'd like to eventually have AC also (still need to plumb the hoses, but thats another project...)...

You've been a huge asset. Seriously. If there is anything I can ever do to help you, let me know. (I throw some mean drywall setting compound and totally rock at rubbing dogs' ears and drinking beer...)
 
LOL Its no problem.

You may need to look more at that compressor, all the dodge units have two wires. From what you're saying it may be easier to buy another under hood harness.
 
Okay, compressor definately has two wires. I'll try to find a pull-apart and get the connections for the ford to and from the pressure sensor, and the one from the dodge to the compressor. I'll see if I can decipher the compressor wiring while I'm in there.

Different topic: How do you have your grid heater hooked up? Mine was originally set up with a grounding push button, but I'd rather hook it up similar to OE, with the heater coming on when the ignition is turned to run from off for a set amount of time. Even better would be based off the intake temp, but I don't wanna get greedy. I'd like the truck to look like it was meant to be this way, not like the whole thing was a hobbled together afterthought
 
Actually, neither of mine have the grids hooked up. My 04 does not have the heater unit at all. I intend to use the intake temp sensor to wire up my 99 though. Its simple to do, but I lost the diagram for it. LOL
 
I kinda figured thats what most people did. I can always just rig them back up the same way, but I'd really rather have them right. Maybe I can just pull them and then justify one of those really slick dual inlet intakes from Jamie.
 
I didnt have any in mine with 240's and a HRVP. If plugged in it would start, b!tch for a little while and even out. Unplugged it would take a few min to start and it would b!tch intensely. Cold here is between 8* and 20* at the worst of winter.
 
cold here will be 25 below when it gets bad, and zero probably every morning. I plug it in, but when its double digit below, I want those grids. And regularly working 10 and 12 hour days, i'd probably be out starting the truck four times a day.

On the other hand, I'd enjoy my days a lot more
 
I could go old school and plumb in an ether bottle into the intake manifold...

I think I'll find a way to use the grids.
 
You must log in or register to reply here.
Back
Top