Wiring Harness GM Part Number Trace

[spentzos]

Hello,

I have a 1967 K20 with a bad wiring harness. It has been piecemealed over the years. I have found a new NOS part. I was told it was for a 1968 (not sure if 67 and 68 are the same). The box states: Wire Assembly Gr. 2.480 1 #8904672. Can anyone please tell me what year this part is for? Also, is it for a basic or full gauge dash cluster?

I called the local dealership parts department and they stated their parts numbering only went back to 1976.

Any help would be appreciated.

Thanks.
Dino
Newport, RI

[1970cstblazer]

Looking through the part number history, the original part number for that harness was 6295305, which became 3938466 in 12/1968, then it became 8904672 in 2/1972. The listed application is a instrument panel harness for 1967-1970 series 10-30 and Blazer with tach and gauges exc. 4 speed. Suggested retail in 1971 was $35.80.

[spentzos]

Thankyou for taking the time to explain this. Did you go to a certain website for this information?

Since the PN states1967-1970 the dash differences (headlight switch placement etc.) will not matter. I imagine I will have to remove the harness tape and obtain the slack for connections.

Has anyone else encountered this using a harness from a later year on a 67?

Thanks again.

[1970cstblazer]

I primarily use GMpartswiki.com.

[pjmoreland]

I've been using the following parts catalog a lot for looking up part numbers.
http://67-72chevytrucks.com/vboard/s....php?p=8890684

According to this catalog, your harness is for 1968 with full gauges, but NOT (EXC, except) 4 SPD, so it has the connectors for a column-mounted neutral safety switch inside the cab.

You could make this work in your 1970 truck. There will be a couple of minor differences though. One is that the fuse panel was mounted horizontally in 1968, whereas it is mounted vertically in your 1970 to make room for the parking brake pedal. This means the big bundle of wires coming from the fuse panel will exit from a different side. With a little work, you should be able to adjust the wires. Also, the connector for the wiper knob exits the harness on the left side of the dash instead of the right. You would need to extend those wires.

[spentzos]

Thank you for the reply.
I'm not sure I understand: "but NOT (EXC, except) 4 SPD, so it has the connectors for a column-mounted neutral safety switch inside the cab."
I have a 67 k20 4-speed. What is required to use with a 4-speed? Sorry for the confusion.

[pjmoreland]

Since it's a 68 harness going in a 67, then the orientation of the fuse panel and the location of the wiper connector will be correct.

I just went through this exact conversion last week because I replaced my automatic transmission with a manual. You will need to reroute the backup light switch wires to the firewall bulkhead connector. These wires can be found on an angled connector that is bundled along with the brake light switch connector and the Neutral safety switch wire. You will also need to deal with the Neutral safety switch wiring. The easy way would be to install a jumper between the two pins of the NSS connector. This connector has two 12 gauge purple wires going to it. I decided to install a switch on my clutch pedal and routed the purple wires to that switch. I now have to press the clutch pedal before I can start the engine. You can see the details of what I did in this thread, starting on post #40.

https://67-72chevytrucks.com/vboard/...=847466&page=2

One other detail that might be problematic is that if you still have the original 67 Ignition switch, then it doesn't have an Accessory position. Your 68 harness has a 12 gauge brown wire that feeds a portion of the fuse panel from the Accessory terminal on the ignition switch. You might need to get a new Ignition switch to go with your new harness.

['68OrangeSunshine]

Some notes that may or may not be relevant --
The SM465 4-Speed in my '68 C/10 has the Back Up light switch on the Drivers Side of the transmission case, to the right of the shifter. I do not know if the SM420 4-Speed -- common until after the 1967 model year -- was also equipped.
My truck has a Factory 4-Speed and there is NO NSS. It will start in any gear or out of gear -- clutch in or out.
When I put a '68 MY grille on a '67 K/10 Suburban [after a deer strike] the bodywork went well, but I found the connectors to the two front amber light buckets in the Grille were different. The '67 = [ / I] and the '68 = [-- I] where one spade connector was angled, while the later one was horizontal. Rather than splice, I R&R'ed the buckets.
So other connectors may also have these little foibles between model years.

The OE IGN SW on my '67 K/10 has no clickable lefthand positions.

[pjmoreland]

The accessory position on my 68 allows the radio to be turned on and I believe the heater as well

['68OrangeSunshine]

Originally Posted by pjmoreland

The accessory position on my 68 allows the radio to be turned on and I believe the heater as well

I'll have to check that out. Took the radio out years ago -- rather listen to my 292. But I can check the Heater out, and maybe the Wipers.


OK. I lied. Ill have to edit my post above.
Vehicle Check results:
'71 GMC --- ACC on: T/S and Wipers work. [Heater is out of order]
'68 C/10 --- Same as above.
'67 K/10 --- ACC, no click there. Key stops at 12 O'clock.

[pjmoreland]

This post has some good info on the subject.

http://67-72chevytrucks.com/vboard/s...89&postcount=6