Maxdaddy1$
New Member
I have no dash lights on my 68 Newport.
Anyone have a good diagnosis plan to id the problem?
Anyone have a good diagnosis plan to id the problem?
No dash lights on 68 Newport
- Thread starter Maxdaddy1$
- Start date
bronze turbine
Active Member
I would check the dimmer switch first.
A plan!! I feel like Sheldon from Big Bang... A plan... I need a white board.
OK, enough of that. Let's do the easy checks that show 99% of the problems first and then go deeper if need be.
First thing to do is turn the headlights on and reach over and run that dash light dimmer switch back and forth. Best to do this in the dark. See if any dash light flickers or flashes. If it does, the switch needs attention and we have an "in house" guy to rebuild them. @Devinism can do a good job with that. Turn that switch all the way until it "clicks" and the dome light should come on. Sometimes the dimmer will clean up a little with use, but they are usually still "fussy".
Next is to check the fuse. IIRC, it's on the end of the fuse block and marked "Inst lps". Pull the fuse and see if it's blown.
Usually it's the dimmer switch that's causing the problem with the fuse being the next culprit. You can see test those without tools or actually crawling under the dash, so they are fortunately the easiest check.
OK, enough of that. Let's do the easy checks that show 99% of the problems first and then go deeper if need be.
First thing to do is turn the headlights on and reach over and run that dash light dimmer switch back and forth. Best to do this in the dark. See if any dash light flickers or flashes. If it does, the switch needs attention and we have an "in house" guy to rebuild them. @Devinism can do a good job with that. Turn that switch all the way until it "clicks" and the dome light should come on. Sometimes the dimmer will clean up a little with use, but they are usually still "fussy".
Next is to check the fuse. IIRC, it's on the end of the fuse block and marked "Inst lps". Pull the fuse and see if it's blown.
Usually it's the dimmer switch that's causing the problem with the fuse being the next culprit. You can see test those without tools or actually crawling under the dash, so they are fortunately the easiest check.
GOLDMYN
Senior Member
first post, we must see a picture of your car and some history, we are a demanding group
Maxdaddy1$
New Member
Okay, where can I provide the history? I did add a photo as a profile pic just now.
GOLDMYN
Senior Member
here is fine, just a thread describing your experience on finding and cars history will be fine
Maxdaddy1$
New Member
Map light comes on when I turn it all the way up.
Gerald Morris
Senior Member
I have a '68, and have worked on the instrument panel lighting a bit myself. If you have the map light when you click the dimmer all the way, then the dimmer is still good.
NOW, you will need to remove the instrument panel for deeper analysis: Download the FSM if you haven't got one. The 1967-68 dash is EASY compared to their lovely but inconvenient forebears of '65-66! You can just unscrew the sundry bezels, faceplate screws and finally the instrument panel screws themselves, and pull them out!
Have at the very least, a test light when you do this.
Your instrument panel has a crude voltage divider to supply much of the instrument lighting. Start by testing current IN to that. The dimmer varies 12V, as can be seen when the map light comes on as you peg it. The wiper and spring on the dimmer accumulate dirt and oxide over the decades, and a bit of good contact cleaner is best used to restore it to functionality. Get some, and some sort of applicator to clean the spring GENTLY. If the map light contactor still closes, as yours does, then the odds are high the dimmer is still GOOD.
SO, you must test the voltage of the power supply! Find it, ground the portions of the dash with alligator clips if they're not in contact with the frame, then test power IN to the voltage divider/power supply, and test what comes OUT of it.
I suspect, given what you described earlier, that THIS may well be the point of failure. If you got this far, replace it with a solid state one! They run around $50. I need to do the same, FWIW....
Lack of proper GROUNDING often causes instrument panel lighting failure. You will have plenty opportunity to correct this now. For the purpose of testing the panel, you can actually remove the whole damn thing to a bench w a power supply, and test it there, but if it isn't grounded well to the frame, it still won't light up. I make bonding jumpers for stuff like this from stranded copper wire and some good lugs. Easy to do, well worth the trouble.
Van carries a solid state power supply for the instrument lights: Fits Dodge Chrysler Plymouth Solid State Voltage Limiter NEW | eBay
Maxdaddy1$
New Member
Wow, great advice. Hope I have the skills to do all that. Many thanks.
If the map light works, but the dome light doesn't, there's wiring issues somewhere. Also, the map light is a simple on/off as the rheostat wheel is turned and not part of the wiper or rheostat coil. The coil or wiper on the rheostat could still be bad (or dirty). It does show that there is power to the switch though.
The voltage limiter is for the gauges. Basically dropping them to 5 volts. It has absolutely nothing to do with the instrument lights. It is a good upgrade, but not part of the OP's problem.
Did you do what I suggested and work the switch back and forth? It's the simplest check that you can do.
Gerald Morris
Senior Member
Yah. There IS power TO that switch. I suggest cleaning it well. Contact cleaner and q-tips if necessary, making sure to remove every cotton fiber after using them. Mine does decent thus. Won't hurt to put LEDs into the instrument panel also. Reduces current demand all around.
The dome light might just have the hot lead dead, given how Mopar switched the door pins to ground. The OP can stick a tester on the dome light, check for a hot voltage, then see of those switched grounds aren't making it to their destination. If the dome light is dead, I suspect the hot TO it is dead, not a door pin. Not having a dome light in my ragtop, I admit being less than 100% sure of how its wired. My '66 was a swtched ground, and I suspect the 68 is too. I know the map light on Gertrude has the switched grounds. I worked in a pair of nice blue LED strips, one on each windshield post on the sides to do for courtesy lighting. Works very well. Ran those into the switchloop and constant hot of the map/rear courtesy lights.
Our OP and others new to working older rides need to know that switched grounds remained normal in Mopars well into the 80s if not until today. I won't comment on how stuff gets wired now.
True. Not directly. But funky old thermo-electric widgets effect funky old circuitboards and such they're connected to. I say ditch the 19th century regulator and put a proper MOSFET voltage reducer/supply in there for that fuel gauge. If any bits of the old board have oxidized, one can use copper foil tape to re-trace them. I did, and it works well.
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Gerald Morris
Senior Member
Here's a quick little test for you: Get a TEST LIGHT, something you can still score for $10 or so. Remove your dome light bulb, then attach the ground of your test light to a SURE ground. Test the light first, to be SURE that when its on a good hot 12V supply, it lights up properly. Now, with your test light grounded, test the dome light clips, looking for the HOT wire. The wire is probably light red or pink. One SHOULD be hot, all the time. so your test light will light up. If it does so, you know the problem with your dome light is the switch loop. These old Mopars use switched grounds! So...
IFF the hot side of the dome light lights up that test light, do this:
Now, using a GOOD 12V source, (maybe even the hot lead to the dome light) attach your test light to the other end of the dome light clips. Open a door. The door pin switch SHOULD close the circuit, causing the test light to light up. If it does, your dome light problem is with just the damned lamp. Inspect the clips, or pins, or whatever they used to make a circuit with some incandescent lamp in the dome light. If the lamp itself was the issue, know that a wide variety of LED lamps abound with which you may replace the old incandescent battery draining one. Use one. I can leave the dome light in my '83 Dodge D150 on for several days with no appreciable loss of cranking power in the cheap AutoZone battery because I use a lamp from SuperbrightLED.com Look this up.
I had the same issue with my '66 Newport, I'm not sure if your '68 is wired the same. I thought I was going to have to take out the steering coumn and dismantle the dash ( because it has air conditioning). My map light and dome light both worked. I changed the headlight switch and Ihave dashlights!
Gerald Morris
Senior Member
Yes, the headlight switch on most C body and other model cars from that era controlled ALL the lighting in the car. I experienced exactly the same symptoms and cure on my '66, and my '83 Dodge D150, which uses a very similar switch. (I could easily adapt it to the same truth be told.)
Some of the C body rides, such as the '67-early 70s stuff, used two switches, one for toggling power, the other for dimming. Our '68 comes thus, and I thank the Lord we got a second instrument panel, complete with switches, and that I scored a couple more switches off eBay, which were actually NEW and another good. One must shop carefully for old parts.....
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