Electrical, Need Help! Please!

[toolboxchev]

Looking for input.

1. I have 3 under dash wiring harness that do not match the colored wiring diagrams in the Colored Wiring Diagrams(courtesy of another member) and PDF copies of 67-72 GM truck Service Manuals. (are these correct?)

2. One of the above listed has come from my personal truck. It has burned up at both the ignition switch and the heater switch wiring connector. Both switches burned on my vehicle. My application is a early production 1970 (Sept. 1969 C-20 Camper Special with Camper wiring.(all Camper wiring is removed from my vehicle) I have a 7 gauge dash. The fuel gauge is always going cuckoo bouncing around. Not a tach dash, nor vac, nor air pressure.

3. I have a harness I am rebuilding and it does not match all the other 3 harnesses at the Gauge Cluster connector. It is wired different at this location and matches the above listed reference material.

It does not match the one (I assume is stock, Original wire tape) I had pulled from my vehicle in the gauge cluster location.

I AM STUMPED ON WHAT TO TRUST. Can anybody shed some light on this issue????

I would greatly appreciate it. Thank you in advance.

The reference material from this site and original chassis service manuals do not show that it is tach dash wiring. Pics coming if needed.

[ray_mcavoy]

Yes, some pics would probably be helpful.

Exactly what type(s) of differences are you seeing in the wire color coding vs. the diagrams? Are there wire colors present in the harnesses that aren't even shown on the diagrams? Or is it a matter of the wire colors not matching up with the gauge cluster connector pin-out?

And for reference, a tach, vacuum, or air pressure gauge shouldn't make any difference in the dash wiring harness. The tach (when present) is hooked up with it's own harness that is separate from the rest of the dash harness and the vac / pressure gauges are mechanical.

[toolboxchev]

Originally Posted by ray_mcavoy

Yes, some pics would probably be helpful.

Exactly what type(s) of differences are you seeing in the wire color coding vs. the diagrams? Are there wire colors present in the harnesses that aren't even shown on the diagrams? Or is it a matter of the wire colors not matching up with the gauge cluster connector pin-out?

And for reference, a tach, vacuum, or air pressure gauge shouldn't make any difference in the dash wiring harness. The tach (when present) is hooked up with it's own harness that is separate from the rest of the dash harness and the vac / pressure gauges are mechanical.

1. I am seeing different colored wires in locations that do not match the diagrams. ( My old harness + 2 extras I have)

The harness I decided to use(4th one) matches the diagrams on this site.

2. Yes, there are colors not listed in my old harness that are not in the correct location according to the diagrams on this site. There are in #4 which I am rebuilding in the correct location.

3. Yes the wire colors are not matching in locations ( my old harness + 2 others) Again #4 harness they are matching both in location and color correct to the diagrams.

Pics are coming, have to charge phone.

[toolboxchev]

Here are the pics from my New Rebuilt Harness. It matches the diagrams on this site.

1. Positions 1-6

2. Positions 7-12

[toolboxchev]

Here is the old harness and pics. It does not match the diagrams, yet everything on the gauge worked before burning the brown and purple wire at the ignition switch.

1. Positions 1-6

2. Positions 7-12

[ray_mcavoy]

Okay, those pics definitely help explain what's going on!

What you're seeing there is the difference between the warning light cluster vs. the gauge cluster connector pin-outs.

Your new rebuilt harness has the cluster plug configured for a warning light cluster. While your old harness has the plug configured for the gauge cluster.

Evidently, the diagrams you have been looking at have been for trucks with the base warning light cluster since you're seeing a match up there with your new rebuilt harness.

Edit: I should also add that your new rebuilt harness can be re-pinned to work with the gauge cluster. You'll have a couple of left over wires ... the dark blue "oil" light wire isn't used with the mechanical oil gauge and the brown "gen" light wire isn't used with the ammeter (battery gauge). But you will have to transfer over a couple wires (the black ones going to pins #1 & #12) from the old harness to keep the ammeter functional. The warning light style harness also has a "bulb check" feature for the "temp" light that isn't needed with the temperature gauge so you can also disconnect the dark green wire from the ignition switch connector (and insulate the end so it doesn't short out on anything).

[toolboxchev]

Well, just got that info, thank you Ray. You have been a blessing! I suspected something was very different on this harness.

[franken]

The color diagrams aren't correct for all years and options as you've found. Early 67 had no side markers, 68 I think only had reflectors and the last two or so years the side markers flashed when the front signals were off. That's just one example.
Still the color diagrams are handy.

[toolboxchev]

Hey Franklin, thanks for the information on the side markers. I forgot about that. Got my new rebuilt harness in last night and checked a few things. Would you have access to those wiring diagrams for the side markers?

I have seen others do the modification under the hood and wondering if there is a difference for stock application?

I am thinking we need some new info on this site posted for all of us to utilize.

[toolboxchev]

Got my rebuilt harness in and working. Was having starter switch issues and start issues until I figured it out.

Turns out the Switches we are getting these days actually ignite the solenoid without going all the way to the right. Something I am not too happy about.

Seen this before. Napa

Shout out to those whom have pointed the way. Would not have gotten there as quickly without the correct advise.

UPDATE: So I had a chance last night to get a good idea of how well my electrical system was working. In the past I had added some grounds to the vehicle and I could tell the entire system was functioning better. My lighting system is now much brighter, esp. could tell with the side markers. I have the Clear Lenses from Cooper Restorations and the little 194 bulbs are much whiter and brighter, instead of yellowish looking.

It was tedious, Stainless brushing all the Packard connectors made a huge difference, plus cleaning all the grit and goo out of the plastic connectors. If you look closely at the brass and copper ends you can tell which one got cleaned.

[studeclunker]

Good advice is indeed priceless!