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I recently purchased an NOS factory-duplicate C4 engine wiring harness to replace the original in my '91. Should I break the old and new ones apart at the bulkhead connector and then connect new to old, or should I pull the old harness out completly by unplugging the ends from under the dash? Unfortunately, I'm afraid that unplugging the ends might require removing the upper dash pad, and I really don't want to create more work for myself than necessary. Someone out there has done this and knows all the tips and tricks!
SnorT91Man
Last edited by SnorT91Man; May 30, 2018 at 07:44 PM.
Reason: Forgot to sign
Unless original harness is severely damaged you don't want to cut it up during the r&r. You need factory manuals to aid in routing new harness and disassembly. You also want to verify harnesses are the same. No missing connectors. Taking pictures or video as you take things apart can help put it together. Zip lock bags and a marker can redure lost screws, connector locks, clips....etc
Unless original harness is severely damaged you don't want to cut it up during the r&r. You need factory manuals to aid in routing new harness and disassembly. You also want to verify harnesses are the same. No missing connectors. Taking pictures or video as you take things apart can help put it together. Zip lock bags and a marker can redure lost screws, connector locks, clips....etc
Hey, man, you're talking to the King of plastic bags and empty pill bottles here! Also photograph everything I do and add captioning to better recall what I won't remember tomorrow. The harness is still in its original GM box, which is at my shop unfortunately. I'll get the part number and a photo or two and put them on this thread in the next day or so.
Hey, man, you're talking to the King of plastic bags and empty pill bottles here! Also photograph everything I do and add captioning to better recall what I won't remember tomorrow. The harness is still in its original GM box, which is at my shop unfortunately. I'll get the part number and a photo or two and put them on this thread in the next day or so.
SnorT91Man
You mentioned NOS-duplicate and having a GM part #. That doesn't sound correct. For a '91 there would be a minimum 4 correct harnesses.
C60 with A4 or M6 (that's 2) and C68 with A4 or M6 (2 - more)
I've never seen a '90+ 'pass-through' right side of dash disassembled. It would be interesting to see what you were sold and how it's assembled.
Brand/vendor and part #?
Is it complete with also the ECM connectors? The pass-through must be very similar to the earlier cars. The pass-through is molded.
Is there a wire bundle that's noted as being the bulk-head pass through?
Snapshots!!!!!!!!!!!!!
Check my reply to the other responder. The new harness has a C100 connector on it with matching wiring attached to both sides. As for the old harness, all the wire bundles from the passenger-side computer in the engine bay feed into the C100 along with lots of other wires. Each of them seems to have a corresponding wire on the other side of the connector, and all of those wires feed through the firewall. I have been so involved in replacing my heater core and carpeting that I haven't gotten back to my wiring problems lately, so some of what I'm saying may not be entirely accurate. Will let you all know later this week.
Check my reply to the other responder. The new harness has a C100 connector on it with matching wiring attached to both sides. As for the old harness, all the wire bundles from the passenger-side computer in the engine bay feed into the C100 along with lots of other wires. Each of them seems to have a corresponding wire on the other side of the connector, and all of those wires feed through the firewall. I have been so involved in replacing my heater core and carpeting that I haven't gotten back to my wiring problems lately, so some of what I'm saying may not be entirely accurate. Will let you all know later this week.
SnoeT91Man
C100 doesn't have wires on both sides - the only thing that has wires on 'both-sides' is the pass-through on right side of dash. If you were doing the heater core it would have been the ideal time to have done it.
Okay, maybe I'm confused... not too inconcieveable! I thought the "pass- through" on the passenger side was the C100 connector. It was the only one pictured in the FSM that looked remotely like the bulkhead connector on the firewall. Regardless, I am kind of playing the heater core removal problem against the rewiring problem and not making much progress on either one! I'm simply trying to keep unnecessary work to a minimum, with the thought in mind that at some future date I might actually be able to drive it again!
SnorT91Man
Last edited by SnorT91Man; May 31, 2018 at 12:14 AM.
Reason: Misspelling
Okay, the verdict's it. My harness is an engine wiring harness for a '91 Corvette. The box it came in had the following info on it: Delco part #12080868 and ID M/T C68. I've vrrified both of these numbers on old parts list sites. I took several pictures of the connectiors and added comments/questions to each one. Please let me know if my assumptiobs are correct. Thank you!
First snapshot is the 'pass-through' right side behind valve cover vicinity.
Last snapshot is the engine harness plug for the C100 behind/vicinity of battery tray etc or near booster.
See 8A-202-12 for C100 explanation and pin outs.
Is your car an M6 with C68?
I would have expected a piece of tape wrapped around the harness near the connector to the C100 (3d snapshot) with likely just 0868 or another 4 digit number that could be used to confirm maybe that it's the correct part in the box. Is there a tape wrap anywhere on the harness with a 4 digit identifier?
Unless 'verified' by connector pinout and hopefully an ID tape you've only ID'd the part# and maybe NOT what's in the box. It should be easy enough though if you're familiar with the FSM. The 8A-201-X section and the 8A-202-X section can be your friend. First thing to check would be the correct connector(s) for the blower control module. If they don't match then it ain't a C68 harness.
WVZR-1 has clarified my identification of the connectors on the NOS engine wiring harness I plan to use on my '91. He also provided several ways to ID the harness to assure myself it's the real thing. I'll check them tomorrow. I sincerely appreciate all this info, but do have one question...just how would I know if my car is an M/T C68? I don't even know what it refers to! I've owned numerous Corvettes since the 1960s and this is absuloutely the first time I've ever heard of these designations.
WVZR-1 has clarified my identification of the connectors on the NOS engine wiring harness I plan to use on my '91. He also provided several ways to ID the harness to assure myself it's the real thing. I'll check them tomorrow. I sincerely appreciate all this info, but do have one question...just how would I know if my car is an M/T C68? I don't even know what it refers to! I've owned numerous Corvettes since the 1960s and this is absuloutely the first time I've ever heard of these designations.
Thanks again for the valuable input.
SnorT91Man
Is your car a 6 speed manual with automatic temperature control?
SPID label on console door needs to show C68 and ML9,
If your car is an automatic the harness isn't correct!
It's a 6-speed but I'll have to check on the auto temp control. I honestly don't remember. I've been rebuilding the car for eight years, some of which included a bout with cancer, a broken right leg, and a fractured left ankle. However, at 76 years if age, I intend to persevere and drive the damned thing in next year's "Cruisin' the Coast."
Pass-through is retained like this. #19 is a rivet that likely just secures the #18 plate. I ain't ever been needed to be there. I don't believe I've ever seen it in the FSM. I may look harder. Maybe someone has snapshots. You might post a snapshot of what's inside of the pass-through. I'd expect C237, C238, C239 & C240 as seen 8A-203-0 FSM
NOS Engine Wiring Harness
