so if the gas and temp gauges don't work...
Download a free service manual here
http://www.forabodiesonly.com/mopar/showthread.php?t=244981
and here
http://www.mymopar.com/index.php?pid=31
MyMopar has simplified but not really complete wiring diagrams but are sometimes easier to follow. They are sometimes wrong, and don't show all terminals and interconnects
Here:
http://www.mymopar.com/downloads/1972/72ValiantA.JPG
http://www.mymopar.com/downloads/1972/72ValiantB.JPG
Here are a couple of partial screenshots out of the 72 Plymouth manual, pages 8-150, and 8-151
Follow from the VOLTAGE LIMITER (12V) over to the harness connector, and out that pin on G5-20 DBL which means arbitrary circuit number G5, no 20 size wire, and it's DARK BLUE off the left of the page. Now look on the other page it comes on the page from the right, goes to "in harness splice" diamond 3, and splices in and goes down to "N" of the bulkhead connector. THIS IS ignition voltage going out to the engine bay
If you were to go back to the no 3 splice, and pick up J2B-12 DBL, this is your IGNITION RUN feed coming from the ignition switch
Pick it back up coming in from the left of the page on 8-151 and you'll see it goes directly to the ignition switch connector
THERE IS NO FUSE anywhere in this circuit, it's only protection is the main fuse link out in the engine bay, which is nearly no protection at all
Download a free service manual here
http://www.forabodiesonly.com/mopar/showthread.php?t=244981
and here
http://www.mymopar.com/index.php?pid=31
MyMopar has simplified but not really complete wiring diagrams but are sometimes easier to follow. They are sometimes wrong, and don't show all terminals and interconnects
Here:
http://www.mymopar.com/downloads/1972/72ValiantA.JPG
http://www.mymopar.com/downloads/1972/72ValiantB.JPG
Here are a couple of partial screenshots out of the 72 Plymouth manual, pages 8-150, and 8-151
Follow from the VOLTAGE LIMITER (12V) over to the harness connector, and out that pin on G5-20 DBL which means arbitrary circuit number G5, no 20 size wire, and it's DARK BLUE off the left of the page. Now look on the other page it comes on the page from the right, goes to "in harness splice" diamond 3, and splices in and goes down to "N" of the bulkhead connector. THIS IS ignition voltage going out to the engine bay
If you were to go back to the no 3 splice, and pick up J2B-12 DBL, this is your IGNITION RUN feed coming from the ignition switch
Pick it back up coming in from the left of the page on 8-151 and you'll see it goes directly to the ignition switch connector
THERE IS NO FUSE anywhere in this circuit, it's only protection is the main fuse link out in the engine bay, which is nearly no protection at all