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devildog

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Hello all. Need some advise on rally dash electrical problem. Bought a '67 Formula S fastback a couple months ago and, of course, it had some issues. Some of the gauges and dash lights didn't work so I looked at the wiring under the dash only to discover it had really been butchered badly. Bought a new M&H dash harness and replaced everything from the firewall with the new harness. Bought 2 circuit boards and replaced them too. As I suspected the voltage limiter in the fuel gauge I also, following instructions, put in an IVR3. Still no dash lights/gauges. Everything else works perfectly! Put a multi meter to the leads on the circuit boards and have zero volts. Looking at the wiring diagram didn't seem all that helpful either. Other than the basic black/red wire codes for DC the traces don't mean much. I am out of ideas and could really use your experience and expertise. Thanks to the group for any and all suggestions.

Devildog

IMG_0298.jpg
 
Great looking car, thanks for signing up. We'll get you purring down the street!
 
Service Manuals – MyMopar
It sounds like you can use a VOM, attached is a link to a free downloadable service manual with schematic. It seems you are not getting power to your dash area. Perhaps tracing the wiring will help. All the best!
 
Welcome aboard, did you get new leads from the fuseblock? Also chk where they connect at firewall/bulkhead connector. I made my dash harness for our 67 and surprisingly there were very few issues.
Beauty car! More pics please
 
Also for schematics there was a supplement for 67 that wasnt included in the factory service manual that Mattax sent me. Pm me and I can email you.
 
devildog said:
Other than the basic black/red wire codes for DC the traces don't mean much.
Click to expand...
Both colors are used to denote hot wires.
devildog said:
Looking at the wiring diagram didn't seem all that helpful either.
Click to expand...
Not sure what diagrams you are looking. The factory diagram identifies all of the circuits, colors, and wire gage. The '67 diagrams are not quite as good as 68 but still pretty good. For '67 the Barracuda diagrams are in the '67 Service supplement 67-25-6.
This should be a direct link to the 67 Barracuda Supplement which has the fastback and rally dash wiring diagram.
http://www.mymopar.com/downloads/servicemanuals/1967_Plymouth_Service_Manual_Supplement.zip
if not, its on this page Service Manuals – MyMopar

There's also pdf of the shop manual diagram by @1969383S in this post.
Make sure you get the '67. There are changes each year.

Diagram wire codes covered here

Off the top of my head, gages are powered directly from I terminal on the key switch.
The instrument lights are powered through the headlight switch, then to the 2 amp fuse in the box, and finally up to the connector on the instrument board.

Two corrections to the factory diagram noted here. The difference mostly being that the wire for the instrument lights goes to the steering column connector first after the fuse box.

One thing in common is the grounding. There was an additional ground for the instrument panel to help insure good grounding.
upload_2020-2-26_17-58-17-png.1715477509

Loose end shown above connected to the bottom of the dash panel under the screw for the radio support bracket.


and
:welcome:
 
69conv said:
Service Manuals – MyMopar
It sounds like you can use a VOM, attached is a link to a free downloadable service manual with schematic. It seems you are not getting power to your dash area. Perhaps tracing the wiring will help. All the best!
Click to expand...
I have the '67 Plymouth manual and the Barracuda supplement. Have wired electronic circuits and done alot of house wiring. Even wired AC and DC circuits on a sailboat but auto wiring seems to be a different animal. Using a VOM is how I knew there was no power going to the circuit boards. The wiring diagram shows 5 orange wires spliced that may go to the gauge/dash light function that were not there in the old wiring and not included in the new harness. Wondering if I need to make one???
 
That is one of the corrections which effects routing but not the function. The instrument lamp feed goes from the headlight switch to 2 amp fuse, then to the steering column connector, and only then to the welded splice.

Look at the link below for my mark up.
Mattax said:
Two corrections to the factory diagram noted here. The difference mostly being that the wire for the instrument lights goes to the steering column connector first after the fuse box.
Click to expand...

So go to the steering connector and back probe that with the parking lights on and the instrument lamp switch turn up to max.
If nothing there, then fuse box.

devildog said:
but auto wiring seems to be a different animal.
Click to expand...

The biggest differences that I think throws people are:
a. that it has two power supplies.
b. the fuse box is not a unified power distribution center.
 
Mattax said:
Both colors are used to denote hot wires.

Not sure what diagrams you are looking. The factory diagram identifies all of the circuits, colors, and wire gage. The '67 diagrams are not quite as good as 68 but still pretty good. For '67 the Barracuda diagrams are in the '67 Service supplement 67-25-6.
This should be a direct link to the 67 Barracuda Supplement which has the fastback and rally dash wiring diagram.
http://www.mymopar.com/downloads/servicemanuals/1967_Plymouth_Service_Manual_Supplement.zip
if not, its on this page Service Manuals – MyMopar

There's also pdf of the shop manual diagram by @1969383S in this post.
Make sure you get the '67. There are changes each year.

Diagram wire codes covered here

Off the top of my head, gages are powered directly from I terminal on the key switch.
The instrument lights are powered through the headlight switch, then to the 2 amp fuse in the box, and finally up to the connector on the instrument board.

Two corrections to the factory diagram noted here. The difference mostly being that the wire for the instrument lights goes to the steering column connector first after the fuse box.

One thing in common is the grounding. There was an additional ground for the instrument panel to help insure good grounding.
upload_2020-2-26_17-58-17-png.1715477509

Loose end shown above connected to the bottom of the dash panel under the screw for the radio support bracket.


and
:welcome:
Click to expand...
Appreciate the help. Won't be able to get back on it until the weekend. The M&H Electric harness came pre-built with all the connectors, including the OEM style fuse box, attached. It's my understanding they bought all the design prints and maybe the jigs for all the Plymouth models. They state it is the "base" harness and does not include wiring for some of the add ons that you could get. So far everything is there except the orange wires that are spliced at a 5 way joint. Think that is what I will have to figure out. Plymouth (and Chrysler in general) kept making wiring changes, even in the same model year. Head scratcher for sure. I thought the IVR3 would solve the problem but no such luck so.... back to tracing.
Thanks again, I will eventually conquer this (no matter how many times I have to remove the dash).
 
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