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are you wanting to know where the grounding is for the battery and electrical path???
the battery cable grounds to the frame, usually frame to motor with another ground cable, black wires on the wiring go to ground in the dash, rear wiring loom has grounds, antenna has a ground to frame, front wiring has a ground up front by headlights, ground usually on tranny mounting bolt for heater motor, some small grounds come off frame to other points. WHAT do you exactly need to know??
The battery cable grounds to the frame via ground cable
The starter grounds to the frame via ground cable
As OP states above, then there are many other grounds whether its the power antenna under the driver's side rear fender or up in the dash. You really need a wiring schematic to trace them all and better to identify the electrical glitches and troubleshoot from there.
4) Front lamp harness: First is at the lower left (driver side) corner of the radiator support facing to the front. This one is a PAIN to access because the vacuum reservoir/frame member is in the way--if my experience is any measure it's also in the worst condition of all the grounding points. Second one is dead center in front of the hood between the headlight vacuum relays--it also has a rubber coated steel wire cable retainer for the harness.
5) Rear lamp harness: Near the radio antenna
6) Cabin harness: Main one is on the driver side "A" pillar behind the dash. There's a secondary one that grounds the power antenna relay on the shifter housing.
7) Power door locks: Passenger side door behind the trim panel near the front.
8) "Bonding" ground: from frame near driver side "A" pillar to the pillar (access from under the car).
9) Alternator: upper rear left of the alternator--bracket that routes hoses is attached at the same point.
Good info. I fear the one on the radiator mount is my issue. Gauges drop to zero when I turn headlights on. Tach/Speedo lights work great but not in gauge cluster. All new parts including bulbs. In consistent ohm reading on cluster ground wire as well. I suspect that is bad connection or broken wire. Multimeter reads zero sometime but only 11-15 ohms resistance at others???
The gauge pack ground comes from the cabin ground on the driver side "A" pillar near the headlight switch. That single ground point is for everything in the cabin except the power door locks and power antenna relay. That ground circuit is FILLED with factory splices.
This is certainly no more fun than it sounds but you need to start tracing the grounds (solid black wiring) in the cabin wiring harness. Presuming yours is '78+ feel fortunate as the dash itself is quite easy to remove. Once the gauge pack, glove box, A/C ducts, instrument cluster and "filler panel" that holds the headlight door override switch are removed you just have to remove a couple screws on each side of the dash and release two clips that you've find up under the dash near the top. One is to the right of the steering wheel, the other to the left of the glove box. If you do have to remove the dash the little "ears" at each front corner between the windshield and "A" pillar are delicate. They originally bent at the crease you see but after decades they're just as likely to break as to bend
The gauge pack ground comes from the cabin ground on the driver side "A" pillar near the headlight switch. That single ground point is for everything in the cabin except the power door locks and power antenna relay. That ground circuit is FILLED with factory splices.
This is certainly no more fun than it sounds but you need to start tracing the grounds (solid black wiring) in the cabin wiring harness. Presuming yours is '78+ feel fortunate as the dash itself is quite easy to remove. Once the gauge pack, glove box, A/C ducts, instrument cluster and "filler panel" that holds the headlight door override switch are removed you just have to remove a couple screws on each side of the dash and release two clips that you've find up under the dash near the top. One is to the right of the steering wheel, the other to the left of the glove box. If you do have to remove the dash the little "ears" at each front corner between the windshield and "A" pillar are delicate. They originally bent at the crease you see but after decades they're just as likely to break as to bend
I have everything you mentioned already out except the dash pad. I expect it’s in a splice somewhere because the tach/speedo lights work fine so if the ground is the one on the a pillar something must be bad between there and the gauge cluster
If everything's out then remove the dash pad. That will make it FAR easier to find the problem in the harness.
With everything out, removing the entire cabin harness isn't particularly difficult. Hint: You free the fuse box by loosening a bolt (5/16" I think) in the center of the connector on the firewall side. If you do this DO NOT clean out the "ugly brown goo". It's dielectric grease. If anything add some more!
With the harness removed you can check everything. I found some of the factory splices (they're plain steel) slightly corroded with signs of overheating as the insulation tape around them was dry and crumbly. I soldered pieces of 12 gauge copper wire across the splices and wrapped them in arc proofing tape. Problem places are around the center console where replacement stereos and other modifications are common and near the horn relay due to it's hideously difficult to access location and extremely stiff securing method both of which make yanking a high possibility.
Hey Karol, you have a spark plug wire missing, might run a little ruff!
