Need Guru: Gauges and Light Switch Issues

[norcal_mike]

I have a 68 Charger and read every ralley gauge cluster thread here and across the web- and I still cannot solve this issue.

My dead gauges came back functioning after I replaced the IVR with the RTE solid state limiter but something along thr way happened and now when I turn my lights on, my gauges drop.

Here is what I did:

1. Gauges were dead: Removed gauge cluster and replaced ivr with rte solid state limiter and installed new rebuilt Dimmer switch from Devinism.

Result: gauges working. Dimmer working . Only clock light works, other instrument lighting not working.


2. Removed cluster and replaced dead bulbs with leds.

Broke a pin on the circuit board. Soldered all pins and tested continuity. Check.

Cleaned circuit board.
Cleaned bulkhead connectors with crc electronic cleaner ; wait for dry then reconnected woth dielectric grease. Dielectric grease used on all connectors.
Replaced fuses and cleaned connectors.
Replaced with led bulbs.

Result:
Gauges working only with lights off.
Turn lights on and all gauges drop.
Clock bulb , turn signal, and Brake Dash Light working.
Speedo, water, oil, amm, gauge lighting not working.

All headlights, blinkers, brake lights, dome, console lights working.

3. Checked and cleaned all grounds ; added new star washers and ensured they are seated in metal with dielectric grease.

New: added a new ground strap from back of speedo gauge to steering column mount.

Result:
Same result, gauges only work with light switch off. Except this time the oil pressure gauge is pegged.

Turn headlights on and all gauges drop(ammeter works fine).

No instrument lights except clock and brake dash light, turn signals.

I also noticed console lights getting very hot to touch.

What am I missing or what did I do wrong?

 

[davek]

could be a bad headlight or dimmer switch and yes I read it was new. Dimmer switch has everything to do with dash lights. How is your ground on the gauge cluster? How is the dash harness?

 

[norcal_mike]

Car is all original and the dash harness is in really good original condition, no splicing or anything. As mentioned, the dimmer switch was bought from a mopar guy who rebuilds them and it sat in my drawer for over a year while I worked on the metal. It’s dimming the dome and only dash light that is working.

The dash frame has never been painted and neither has the gauge housing, I added an additional ground strap this morning and it pegged the oil pressure gauge.

I just pulled out the cluster again and checked to see if the circuit board pins were grounding out to the housing because I back soldered a 14g wire to the pin- negative not grounded.

I discover that the IVR connector to the oil pressure gauge has continuity to both sides of the oil gauge. Is this normal?

I did notice that one of the bulb socket housing was deformed from heat- I cant confirm if this is recent but I think it might be. I am pretty sure when i removed the cluster all of the bulb housings looked fine.

Should I throw a new headlight switch st it?

 

[Dodge33]

Contact member " devinism " here on this site. He does beautiful work on rebuilding dash switches, any one of them, for
68-70 B body cars. They will function better than new!

 

[norcal_mike]

Contact member " devinism " here onthis site. He does beautiful work on rebuilding dash switches, any one of them, for
68-70 B body cars. They will function better than new!

The new dimmer switch IS from Devinism.

 

[davek]

The new dimmer switch IS from Devinism.

Ask Devinism how to bench test the dimmer switch. Might off got damaged in transit.

 

[pnora]

You are losing the ground. Install an auxiliary ground to the circuit board.

 

[devinism]

It almost sounds as if wires in the gauge c-board plug have somehow gotten switched?
And just for grins... have you tried swapping in a different, or old ivr? I know this one is new, but you never know.

 

[norcal_mike]

You are losing the ground. Install an auxiliary ground to the circuit board.

I will try this.

 

[norcal_mike]

It almost sounds as if wires in the gauge c-board plug have somehow gotten switched?
And just for grins... have you tried swapping in a different, or old ivr? I know this one is new, but you never know.

Are you referring to this? Looks correct according to the wiring diagram. Confirmed the colors all the way to the sending units. I don’t have another IVR, pretty sure the one I pulled was toast.

 

[pnora]

If you have your cluster out post some pics of the back side.

 

[norcal_mike]

If you have your cluster out post some pics of the back side.

 

[pnora]

Looks ok at a quick glance. Install a ground here. You could bench test everything before putting it back in. Were the screws holding the board down in place when you were seeing what works?

 

[norcal_mike]

Looks ok at a quick glance. Install a ground here. You could bench test everything before putting it back in. Were the screws holding the board down in place when you were seeing what works?

View attachment 1880978

Yes the screws were all in place.

 

[pnora]

Yes the screws were all in place.

I would get some test leads made up, get it all together, and bench test it.

 

[norcal_mike]

I haven’t had the time to bench test yet.

I did check continuity from the fuse box to the instrument bulbs, headlight switch, dimmer switch, circuit board pin, and emergency flasher.

There is continuity to all the plugs EXCEPT for the red wire on the Flasher; is this normal? My flashers do not work.

Looking at the wiring diagram in the FSM, I think this wire goes to the turn signal switch, both signals work btw.

Inspected the dash harness and it looks really good condition. I did not cut away at the loom, only inspected visible wires.

 

[pnora]

I haven’t had the time to bench test yet.

I did check continuity from the fuse box to the instrument bulbs, headlight switch, dimmer switch, circuit board pin, and emergency flasher.

There is continuity to all the plugs EXCEPT for the red wire on the Flasher; is this normal? My flashers do not work.

Looking at the wiring diagram in the FSM, I think this wire goes to the turn signal switch, both signals work btw.

Inspected the dash harness and it looks really good condition. I did not cut away at the loom, only inspected visible wires.

I would fix one thing at a time. Flashers are a separate issue and I would start a new thread when you get into fixing them.

 

[norcal_mike]

I would fix one thing at a time. Flashers are a separate issue and I would start a new thread when you get into fixing them.

Ok noted, thanks.

 

[norcal_mike]

Woooohoooo! Success! After bench testing the gauges, I removed the extra ground from back of speedo to column support and added a ground strap from back of circuit board to dash frame ; credit to @pnora , and now I have cluster lights and the gauges stopped dropping when I turn the headlights on.

(I sshould add that I had to r&r thr cluster 3x to fiddle with the bulbs, rotating the leds on the board tonget all 4 to illuminate)

I am not sure the gas gauge is working, I have about 5 gallons in there; I will check the ground at the tank tomorrow.

Also, not sure if the speedo bulb is working; seems slightly dim on the right side of the gauge. This could be an illusion as the speedo gauge is really oxidized compared to the clock face.

The other weird thing thay happened when I reinstalled thr cluster- I forgot to pull my battery terminals. Car started up , idled for a few seconds then died. Couldnt get it to fire up— eventually discovered my fairly new MSD coil didnt have spark. Pulled an old Pertronix coil from another car and it fired up right away. Coincidence or related? Done for tonight.

Thanks to everyone for their input.