Dodge trucks from this era are notorious for bulk head problems, the B bodies not so much. Like I said a few posts back, whip out the ohm meter and the wiring diagram.

Fun with connectors: the female side is held in the hood by a small tab that's part of the spade head. Connector hood has a small opening where ya can shove a small flat head in and release the connector from the hood. Bend the tab back up before reinserting or ya get what Gene had. The male side can be released by squeezing it together to release the 1/2 of the spade that acts as a retaining clip. Generally pop right back in. OEM style connectors can be a hunt but that's were a spare / scrap harness comes in handy.

Thank you, RWG75, that will be a help since my books only showed as shipped yesterday. Will start testing connections this weekend.

Did wonder...what is the silver relay (?) at the bottom (in photo, right) of the bulkhead? Feels like it's trying to come apart when it's touched.

Off the top of my head I'm thinking headlight circuit breaker. The other (empty) mounting location would be power window.

Possibly a key light or buzzer relay. Headlight circuit breaker is built into the headlight switch.

key / seat belt buzzer is behind the ash tray. the good book says horn relay.

Pulled the bulkhead connector that covers the gauges. Everything feels fantastic, not loose, all wires are pushed in solidly, nothing is wiggling, no corrosion. I see no damage (those dark marks on the female end cleaned off, not scorched). Put everything back together after a quick clean-up with contact cleaner. Nothing.

Still stumped.

As I understand, the gauge cluster grounds to the housing itself. I know I'm getting power to the gauges for sure...when I hooked the battery up and keyed the power on, I saw the oil pressure gauge tick up slightly and stay there, and with the fuel tank and sender out the LED is still flashing away for low fuel. Is this looking like a case of adding in a ground at this point?

I spent ten years wiring helicopters, and Chrysler gauge clusters just kick my .

Would there be a chance the gauges are maybe fried? I can lend you some to test. Who knows.

It's usually easier when ya have the schematic or 1/2 of it memorized.

The ground for the dash is in the 6 pin connector more or less behind the speedo. Solid black wire in the middle. Other end is a ring lug to the dash frame more or less behind the ash tray (CI 34). Ground side of gauges, dash lamps and voltage limiter are tied together in the circuit board. So if the lights light, ya got a ground. An easy sanity check is one lead of the ohm meter to a handy body ground like the A pillar trim screw or visor mounting screw and bounce around the front of the cluster with the other lead.

Not surprised the bulkhead connector was clean - sealed up pretty well from the factory and well hidden from rain water. The connectors at the sender for temp, oil, fuel are more likely culprits. Push on plug for temp sender is often rusty, spade connector for oil is often loose / corroded / hanging on by a thread, ground strap at tank is always rusty and will often just crumble in your hand. At this point, it's divide and conquer - check continuity from bulk head connector to senders and from bulkhead to circuit board.

Just remembered this one: one of mine had a problem where every now and then the dash lights didn't light. Usually in cold weather and eventually came on. When it turned in to a hard fail, reseating that 6 pin connector (CI 5) fixed it - the orange wire across from the ground is the dash lamp hot. If the stray jumpers from way back was an attempt to fix a flaky ground, I bet it's right there.

There ya go and DynoDave called it a few posts earlier. Yanking the entire carrier to get to the back side isn't too ugly.

Sounds like a plan. Will keep y'all updated on the progress. Thanks for the help and the insight!

Ya know, that's just plain wrong. Ignition on, motor off, oil gauge shouldn't move at all. Fuel sender unplugged, low fuel light should be constant on - I've never seen one that intentionally blinks. If's supposed to come on at 1/8 tank which is about 11 ohms at the sender. It will wink on and off when the fuel sloshes around but the gauge is dampened so it doesn't just bounce around constantly. I think I'd be close to yanking the cluster and putting the circuit board on the bench.

This is a pretty comprehensive gauge diag vid for 75-80 dodge trucks and mostly shouldn't be anything new. B body gauges work the same way, just different hardware. One thing I didn't pickup on when I stashed this away - he started with an oil sender for an idiot light then switched to an oil sender for a gauge.

https://www.youtube.com/watch?v=7X8Tiess12k

Now that brings up something! The wire that is shown in the video that goes from the voltage regulator to the condenser...that I haven't seen yet. In my situation, the random black wire that is routed down to the radio bolt was hooked up to that regulator. I'm not calling it a smoking gun, but if that's the way it's supposed to be connected, suddenly I've got a fairly good hunch as to what is not right.

Found some things I'm not liking. First thing's first, a video of what the gauges are doing under power:



And a close-up of the six-pin connector location. The two blue arrows point to elements on the circuit panel that were pulled up from the panel, but those don't bother me as much as the red arrow, where the plastic has melted, moving the circuit panel's connector away from the plug. Additionally, the brown wire (when viewing from the seat, right side center) had a completely flat contact, no bow to it at all. That was fixed before the video was shot, as was the layout of the loose elements.

I'm still working out where the ground wire for the voltage regulator is supposed to be, but with heat and humidity both in the upper 90s here, I'm only working in my shop a few minutes at a time.

Today's work. First up is the rogue black wire that ran from the voltage regulator to the cluster frame underneath the radio. Three strands of copper were trying to do the job.There are three major routes to the voltage regulator: the two connectors within the circuit board and (G1 20DGN), which runs to the radio's (20 R) power wire. The radio's power connector is hooked up, so that leaves me with the question: on top of the voltage reguator, as I'm looking at it mounted in the dash, is that a simple ground? If so, it's too easy to make a new ground wire and run it to a better location. Otherwise, what goes there?

Second up was removing the front seat, because at 6'3 and pushing the far end of the 200-pound range, contortion is not in my repertoire. Removing the seat, I found that the seat belt buzzer link for the seatbelt itself was not connected. Some under-carpet fishing found the connector and I hooked it back up. The buzzer worked regardless, but I have to wonder if there is a grounding effect here. Either way, I hate purposefully disconnected electronics, so that's done.

Next, I popped out the (C1 4) 12-pin connector and immediately noticed the red/white wire's flat and shallow contact bar. This is the ammeter power wire, which connects straight to the bulkhead (CE 1) port just like the ground wire.

Plan of attack: Make a new ground wire for the voltage regulator and route it to a more trustworthy ground point than the cluster cage, reassemble the functional gauges and test functionality. Will return with findings.

Ok, now we're fixing this thing and popping the cluster might be on the horizon. Easier than layin in the car at any age but I hear ya.

The cap across the vr isn't a ground route it's a filter for the vr clicking. Ground to cluster is still through that smoked connector, fix that and bobs yer uncle. Unplug the new fangled seat buzzer was a typical day 2 thing. Ya can melt a little plastic back in there but at least try heating it up and nudging it back. If committed to to adding a dedicated ground, flip ckt board over and solder a wire to that trace.

Dash pad is 5-6 screws (2 ends, 3 bottom) and 3 screws at defrost grille. Carrier is 3 screws across top and two at the bottom. Pull forward, 2 white clips hold harness to carrier.

Will return with fully functional gauges. vid edit: ya said watch temp, ya meant oil.

Was afraid of that. Those defroster plate screws were put in by the Marquis de Sade himself. Ok, will be the next item up on the agenda after I cool off and rehydrate.

Offset Phillips or 1/4 ratchet and tip. Small flat head under grille. Sucks less.

Well...that was "fun". But it's out. No broken connectors, no separated vacuum lines. That's a win.

Detail shots. Will start ringing this out and see if I can locate the issue.