C100 wiring

DaveP

DaveP

Active member
Re: C100 wiring

canadian said:
Now, does anybody (*cough*DaveP*cough*) have a [] way to split the firewall grommet in order to be able to remove wires without having to clip them?
Click to expand...

I've worked with the P101 grommet this way on numerous harnesses.
  • Remove the tape from the wires on both sides of the grommet. Measure the location of the grommet from the end of the harness. (I got DesertSy's grommet about 8" too close to the ECM end, and the wires aren't long enough now to easily put the ECM back up. Learn from my mistake.)
  • Lube the wire bundle with WD40. Grab the bundle in one hand, and with the other, slide the grommet a few inches one way or the other. It will slide on the wires.
  • Remove the remaining tape that is now uncovered.

If you wish to remove wires, remove the pin from the ECM connector. Gently fold the retaining latches flush with the body of the pin. Lube the bundle again, and pull the wire out of the grommet. The more wires you remove, the looser it becomes. If the grommet is cold, place an incandescent bulb near it for a while to warm it up, and make it more supple.

Don't forget to reposition the grommet the correct distance from the ECM connectors. Retape the harness, and call it done.

No need to cut the grommet. The wires slide out. One could probably get wires back in too, if some are already removed. I doubt wires could be added to a stock-count bundle. It's tight.

Nice thread, Warren.
 
canadian

canadian

sy in progress
Re: C100 wiring

DaveP said:
Connects to a matching connector in the front lamp harness. Contains circuits for the ABS.

blk/wht 450 = ecm ground at rear of LH head.
Purple 420 = brake switch. 12V with brake pedal released, 0V with brakes applied.
White 852. = ANTILOCK light in cluster
Click to expand...

Ok, great. I've removed the ABS so I'll take this out too. Since the truck has run without issue with it removed for years, I won't sweat the missing ecm ground. Should I?
 
canadian

canadian

sy in progress
Re: C100 wiring

DaveP said:
If you wish to remove wires, remove the pin from the ECM connector. Gently fold the retaining latches flush with the body of the pin. Lube the bundle again, and pull the wire out of the grommet. The more wires you remove, the looser it becomes. If the grommet is cold, place an incandescent bulb near it for a while to warm it up, and make it more supple.
Click to expand...

Nice. I go back and forth between removing the wires and just removing the plug and hiding the wires in the loom. I'll give this a try and if I can easily do it, I'll remove them. I always worry I'm going to remove the wrong thing and need to put it back!
 
DaveP

DaveP

Active member
Re: C100 wiring

canadian said:
Since the truck has run without issue with it removed for years, I won't sweat the missing ecm ground. Should I?
Click to expand...

Circuit 450 is blk/wht stripe ground. It goes to most ECM controlled sensors and relays. It is a #12 blk/wht wire at the rear of the LH head. Most grounds on 450 are at logic-level, not battery level voltages.

Circuit 150 is solid black. It is a #10 wire at the thermostat housing. Cir 150 is most 12V level grounds from inside the truck. Lighter, Inst cluster, Radio, Dash lights, Horn, etc.

The two ground circuits are separated to prevent "ground loops" that can cause weird voltage and RFI interference issues in sensitive electronic equipment. Like ECM's and Stereos. They both need to be hooked up to the engine block.
 
canadian

canadian

sy in progress
Re: C100 wiring

Does anybody have a manual handy that shows the GM Delphi part numbers for both the bulkhead connectors? (C100 and the headlight harness)
 
DaveP

DaveP

Active member
Re: C100 wiring

Here, Warren:

12020184 = Bulkhead. On the firewall. C100.
12020100 = Fwd Lamp connector. Plugs into above for Lamp Harness the goes forward along Left fender.
12020183 = Engine Harness. Plugs into C100. Engine harness.

I got these out of my 1993 S/T Helms Manual. I did not attempt to verify these numbers. HTH.
 
gstacky

gstacky

Member
Re: C100 wiring

Hey Dave or Warren, have either of you guys attempted to remove the pins on the engine side C100 connector? I'm building a harness and would like to remove some wires that have been cut and replace them with complete wires rather than splice them.
 
DaveP

DaveP

Active member
Re: C100 wiring

They come out, I've done it many times. Pry out the white 'comb' retainer. Use a flattened big paperclip and go in from the connector side to release the retainer tab on the pin. Pull it out from the wire side.

The tar-goo sealant in C100 is a messy distraction to working with this connector. You have to figure out which side the tab is on, you can't see it because of the goo. Look for the 'recess' in the plastic. This is the release side. Once you figure this out, and a bit of practice, they'll come right out with little fuss.
 
gstacky

gstacky

Member
Re: C100 wiring

Is the white "comb" retainer on the wire side? I think that may be what I'm missing, I'll look for that, thanks Dave
 
DaveP

DaveP

Active member
Re: C100 wiring

Here's a couple of pics that show the retainer "comb". The wire hood covers it when everything is assembeled. The second pic shows the comb partially extracted.

If you overlook removing the comb, you'll NEVER extract the wires / pins.

In this pic, the comb is the vertical white line about an inch right of the wires and goo.



 
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