where to start on faulty ground

[c300g]

i've been having a hard time with the electricals in my 65 plymouth. ive checked all the bulbs. they all work. the dome light does not work. the fuel, alternator and temperature gauge lights are extremely dim. the high beam light does not work, the speedometer lights are super dim along with the radio light. the radio does not work either. i have a feeling its a ground issue but have no idea where to start. any ideas? there are a lot of wires under the dash.

oh yeah, the fueses are all ok as well.

 

[traintech55]

What I like to do is use a test light with a long wire and hook the end to a good positive connection, and start checking. Look on one side and then the other. You would be surprised how many places corrosion can hide itself.

 

[jollyjoker]

You might want to look for a blown "in-line" fuse. I spent days once trying to track down a bunch of weird symptoms in my 65 Dodge (i.e., push in the console cigar lighter, and the C-pillar lights would come on, etc.). Tracked a bunch of different wires all the way back to the fuse block source (all good) - then finally realized that there was an extra "in-line" fuse in the loop. Sure enough - blown! Replaced it, and ALL of the problems vanished!

Guess my main problem was that I forgot that DC current can flow both forward and backward. So, when that "in-line" fuse blows, the current starts sneaking in backwards from who-knows-where.

Sorry I don't have a Fury FSM diagram, so I can't tell you if you have any "in-line" fuses, or not. But certainly worth looking for. Mine was up under the dash, maybe 8-10 inches from the fuse block.

 

[Big_John]

i've been having a hard time with the electricals in my 65 plymouth. ive checked all the bulbs. they all work. the dome light does not work.

The dome light has power going to it all the time and gets the ground feed from the door switches. First thing is to check power (remember it's there all the time) at the dome light itself. If you have power there, unscrew one of the door switches and ground that wire. Your dome light should light.

the fuel, alternator and temperature gauge lights are extremely dim. the high beam light does not work, the speedometer lights are super dim along with the radio light.

Except for the high beam indicator, the instrument lights are tied together. When you move the dimmer, do they brighten or go out? Twist it back and forth a few times. Usually, if the lights are lit, the issue is the dimmer being worn and oxidized. They can be rebuilt and a old one that's been rebuilt is always better than a new replacement.... and cheaper too.

The high beam indicator is another issue and I suggest checking for power at the socket and then work back to the switch.

i have a feeling its a ground issue but have no idea where to start. any ideas?

Download a FSM here: MyMopar - Mopar Forums & Information - Service Manuals . That will give you a wiring diagram.

A digital volt meter is your friend here and can help you diagnose a lot of this. The key is to work on one bit at a time.

 

[live4theking]

The key is to work on one bit at a time.

All of what Big_John said is spot on, but what I quoted above is most important.

 

[OneEyed]

Another idea is to get a length of wire with alligator clips and make your own temporary ground to chassis from whichever point you're testing...see if things start lighting up for ya.

 

[BillGrissom]

Yes, run a ground from BATT- post. Also measure the voltage drop from body ground points to BATT-, while the light is on. If <1 V, ground isn't the problem. Many A-body guys run a ground wire from the instrument cluster to a solid ground screw under the dash, which often helps. Perhaps your supply feed is the issue. Most lights are on the ACC circuit. Insure your key switch passes 12 VDC thru in ACC position. I think there is an "ACC junction" in the dash wiring harness (black wires). In my A-bodies, that is a mess of copper wires "sort of welded" together and wrapped in friction tape. It was a bit green and corroded. Probably the same in my C-body. At least in 1965, your firewall feed-thru is probably fine since via dedicated bus-bars in the terminal. But, wouldn't hurt to unscrew, sand and coat w/ dielectric grease. Remove BATT- terminal before leaving any hot wires dangling.