While diagnosing other electrical gremlins I had my door open while testing my blinkers and hazard lights. I noticed that the dome light got dim and bright as the blinkers went through their cycle. It was even more noticeable with the hazards. Anyone ever experience this? Does this sound like a ground or component issue? I see from the service manual that power to the dome light and the stop light switch come from the same place, so there is a relationship there.

I had the same problem, after a lot of components changing, I found a factory splice in the engine harness ( if I remember correctly coil to ballast resistor to fuse panel wire is spliced) re-soldered it, solved

This is a product of too small of a feed wire in gauge. Its called voltage drop. It is why the headlights are dim too at idle. Also all the connectors offer up a resistance too.

With the engine off voltage at the dome light is at 11 volts +/- 1 volt and when you put the 4 ways on you may see the voltage drop to 9 - 10 volts and then when the 4 way bulbs are out it will wink to the 11 volts again. But start the car and now the altanator is pushing 14.5 volts and that extra 2 volts does make a difference.

Just to expand on wire gauge and voltage drop. On my 65 Barracuda the book says my headlight wires are 18 Gauge. This is too small for the wattage draw in amperes. It should be about 14 gauge at 12.5 volts. And the voltage must go from the engine side of the firewall thru a Bulkhead connector inside and then thru the headlight switch, then back thru that bulkhead connector a second time. So I wire in a relay system and feed the headlights directly with a 14 gauge wire right from the lug on the starter relay. Bigger wire gauge and less connectors makes the headlights MUCH brighter.

Same thing on my son's 1974 D200 pickup. The book says the headlight wires are 18 gauge. But I cut them and stripped the plastic insulation off and did a measurement and found that the wire was really 20 gauge. Way too thin of gauge.

Wire is costly for a manufacture. Thicker gauge wire cost more. So they use the thinest to just get the job done. No reserve in power rating. So when I do a rewire job on a daily driver I will replace all 18 gauge wires with a 16 or 14 gauge. Any 14 gauge gets a 10 gauge if I can. All starter cables get upgraded to 2 gauge.
But wire also adds weight to the vehicle so this is why we have common chasses grounding. The better would be a true return ground wire for every item but this extra wire adds cost and weight.

it was somehow "normal" back in the days, now with aged conections and wires, even more. A low charged batt will make that even worst. With engine running the dimming on these is reduced because the increased voltage up to 13-14 rate. In some cars you can even notice the radio volume going up and down while blinking because on these the Radio feed is shared by the tunring flasher

Hazzards are a big suckers.

As I allways say, if you make mantenience on brakes and fuel system, electrical needs that too after 50 years. But, nobody uses to care that and think electricals will survive forever.

Relays are your friend.....

Joe

Flasher is allmost a Relay by itself. However a relay after the flasher won't work because flasher requires the bulbs load to work. A Relay before the flasher makes allmost no sense because there is not a trigger to make it work really. The hazzard one would be allways engaged, while the turning, will be engaged as soon you put the ign switch on.

Now, a trigger for the dome light.... well I would preffer to make the right thing which is a propper electrical system mantenience. Relay for dome light will solve the problem for it but won't fix the real problem.

Wondering when ppl will stop to patch the electrical stuff instead get deep into the deal to fix the worn and damaged parts!

I think the 'Relay' comment is more directed to doing a Headlight rewire. You can get a nice H4 'Chinese' made one for $10 off Ebag but if you use one on a 6024 or 4656 headlight you must move two pins as a H4 and 6024/4656 use the same connector but for some reason they flipped two pins, Low beam and Ground pins.
H4 headlight relay kit:

https://www.ebay.com/itm/Headlight-H4-Headlamp-Light-Bulb-Ceramic-Socket-Plugs-Relay-Wiring-Harness-Kit/273763423866?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

I do repairs as needed and if its not a 'Points Show' car I will cut old wires out and replace with better quality and replace bulkhead connectors as needed. I order 45 sets of the bulkhead connectors at a time to have some on stock. Bulkhead connectors also work on most spade connectors all over the body of a Mopar.
Bulkhead Connectors:

https://www.ebay.com/itm/Mopar-Male-Female-14-16-AWG-Gauge-Wiring-Harness-Terminal-Crimp-Connectors-NOS/192502001151?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

I have two 4X8 foot sheets of 5/8" plywood here. On sheet 1 is the wiring layout where I took a 1964 Studabaker Daytona's wiring harness and used brad nails to make the layout. I then replaced 1 wire at a time, put new connectors on and rewrapped with glue-free vinyl tape. I pulled the brads out but my ink pin marks are still on it. Flip side in my 1965 Barracudas wiring layout. Second sheet is my 1978 Little Red's wiring and flip side is one for 1984 L body Omni/Charger

I installed 6 relays on my car. One for each AC-heater speed ( four ) and the other two for headlights, but all relays are into the cab hidden down the dash without cut a wire ( I didn't want a single relay visible ) All just relocating the stock terminals from switch plugs to relay plug and jumping a wire ( same color ) to continue the original trace. But I made it mostly to save switch points. My headlights are halogen sealed beams with sucks more power than regulars, and the AC blower switch plug allways got melt on my 74 due the poor contact made inside. I, still using original wiring and terminals to handle the power. I did of course the complete wiring and terminal mantenience of course, and replaced terminales where needed.

I think these are likley the issue.

I would start by slowly/carefully removing the Bulkhead connectors on the firewall. Clean all the male spades using some emory cloth. Don't go over board, just knock the darkness off so the brass kind of shows. It does not need to be shiny.
Then use some Di-electric grease on the spades. This is also called 'Bulb Grease' in packets at Autozone. 3 packs should do it.
On the firewall side female spades clean then as best as you can with the emory clothe folded small to insert in the female part using care not to get the emory cloth stuck. Blow out with compressed air or "Keyboard Dust Off'. Put the connectors back together and see if that helped.

Then, the door jamb switches are hard to get too but clean them up and make sure they are solid grounded.

Something as simple as the old fuse in the fuse block. Clean the fuse lugs and put in a new fuse. The old one may be slightly bad but looks OK.

This uses to be my procedure:

Clean the terminals with degreaser, gasoline or diesel and a brush, then brush and soap to remove the oil products... sink the terminals on vinegar and salt solution for 4 or 5 hours ( this will eliminate rust and sulfated areas which previous cleaning process won't eliminate ), then a baking soda solution to remove acids and you will be good to go!.Brass will change a bit the color from yellow/gold to orangish but the metal will be nicelly exposed back to get good contact.

bulhead and insulators needs to be deeply cleaned too. If not, you'll get bad contacts again.

we are talking about 50 years of abuse and forgotten systems.

try to keep original terminals were is posible. The factory crimping will be allways way better than any crimp you will make at home. If some terminal needs a replacement, crimp and sold will make the best job.



I even used small 180 grit sandpaper pieces to insert and clean inside the curvatures ( inside the "claws" ) of the female terminals, one by one

but If I have had one of these on hands, maybe was used that



BTW I also get tight a bit the female outer claws with a plyer to catch tighter the male end once is inserted

Go to AMazon and look up De-Oxit D5. Its the old Caig Laboratories Cramolin. I used to use the Red R100L and Blue B100L which were red and blue cans. It looks like the De-Oxit is the just the red. The red was the cleaner and the blue a protectant. In general, the D5 is good alone.

Old harnesses and dirty bulkhead connections will do that. I replaced all the wiring in my Duster when I built it and I don't have issues like that anymore. It used to do the classic Mopar light flicker when the turn signals were on and the headlights dimmed at idle. The factory wiring setup in these cars combined with the weak sister alternator that the factory put in them left them with zero margin for corrosion.

All good advice, replace as many bulbs as possible with LEDs and it will greatly reduce the current drain and reduce voltage drops.

But that doesn't fix the problem, just makes learn to live with it. Nice to have led bulbs if you want ( I'm not a fan of those, but at each own ), but terminals issues will be still there just masked with the less load devices.

Stop hidding the problem and go for it!

Knock knock. Jeffaary, ya home?

There is a lot of good informational posts above. And as NachoR said, ignoring it may lead to worse outcome down the road. I have replaced many bulkhead connectors due to burning out and almost smoking the whole car/truck.

The Bulkhead spade connectors are so easy to pull out of the plastic housings. Do 1 at a time. Clean it and reinsert it in its home port. See picture 1 below.

If you need to replace a connector I can also show how to get as good or better connection as a factory crimp. You can still get new Bulkhead spades in 12 gauge and 16-14 gauge from Ebay. You get 15 sets of Mail and Femail 16-14 gauge for $12 and free shipping in USA. The 12 gauge you get 15 sets for $16 free shipping.

The 16 to 14 Gauge:
https://www.ebay.com/itm/Mopar-Male-Female-14-16-AWG-Gauge-Wiring-Harness-Terminal-Crimp-Connectors-NOS/192502001151?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

The 12 gauge:
https://www.ebay.com/itm/Mopar-Male-Female-12-AWG-Gauge-Wire-Wiring-Harness-Terminal-Crimp-Connectors-NOS/192502008508?hash=item2cd2038abc:g:whgAAOSwPoZaxOkB

Thanks for all the input.

FYI I’ve already done a lot of fire hazard prevention; headlamp and roadlamp relays, voltmeter conversion, solid state voltage regulator, and LED lights almost everywhere.

Looks like bulkheads and fuse block are next...

It should have been the first LOL.

Voltimeter conversion is not a need, but this will be an endless discusion along the eternity LOL.

Oh well, and of course, the ground checks in all 4 corners! This is about everything.