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Dash and Interior Light Hiccups (1970 Javelin)

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FreeMoCo2009 View Drop Down
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    Posted: Oct/10/2020 at 10:56am
Howdy folks!

Pardon this post if it's repetitive, but I couldn't find another thread on this topic. I've been going through the wiring in my 1970 Javelin and getting all of the interior lights sorted slowly but surely. All exterior lights work (turn signals, headlamps, taillamps, reverse lamp, etc), and got both the front and rear courtesy lights working in the interior, but I discovered that the other dash lights are nonexistent. I've tested the bulbs, they're in working order, and everything is in a complete circuit according to my test light, but I'm at a loss. Some specifics below in case that helps solve the mystery...

-Lights that aren't working are the lights behind the Wiper and Headlight switches, all of the gauge cluster lights (standard Jav SST guage cluster, so just the speedometer, temp and fuel gauges), the map light, the shift indicator light and center console courtesy light (center console car with an automatic)
-Lights that are working include the two front courtesy lights, the two rear courtesy lights, and (amazingly) the door buzzer.
-All the fuses and door buzzer activator switches have been replaced.
-Car has it's original wiring harness (I know, cue the internet cringe now...) All new fuses, and a handful of parts that were missing/broken have been replaced (including the brake switch, turn signal solenoid, emergency flasher solenoid, and a handful of others I'm likely forgetting. Gotta go through the receipts).
-Car is a 1970 Javelin, 360, Automatic with AC. Engine and Trans are currently out of the car being rebuilt. Don't know if that might affect anything, but hey, the more info the better.

Electricity is like a foreign language to me, but I've been doing what I can with it from information I can dig up online and through the TSM and an electrical circuit diagram. They've helped a lot with getting most of the issues I had previously fixed, but so far this one has stumped me. Always happy with a little extra education if anyone can provide.

Cheers!
-Brad L.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote george w Quote  Post ReplyReply Direct Link To This Post Posted: Oct/10/2020 at 11:41am
Brad. It sounds like you're missing the return ground path of those non working lights that are part of the instrument cluster and other dash and console related lights. The instrument cluster gets it ground through the round plug in connector on the back. The ground is the solid black wire. It goes back into the wiring harness and connects to other black, ground return wires for the lights you mentioned. You'll want to follow the black wires back as I believe they come together and ground to the body in the A pillar area above the parking brake and just behind the dash.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mramc Quote  Post ReplyReply Direct Link To This Post Posted: Oct/10/2020 at 5:46pm
There should be an orange wire that is the power wire for the dash lights too. That needs to be checked out also. At least the wires orange on my 69 Javelin and 74 Matador coupe. LRDaum
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bigbad69 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/10/2020 at 8:19pm
The brightness of the dash lights, the ones you're missing, is controlled by the headlight switch. There is a rheostat on that switch that does this and it can get dirty after 50 years. Have you tried tried turning it back and forth a few times? It might just be a bad contact.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FreeMoCo2009 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/24/2020 at 9:59am
Update:

Apologies for the delay, folks, been busy with other projects as well as the Javelin, but have finally gotten some garage time in my schedule again! So far, still more head scratching.

George- Tested the ground connections, everything appears to be in working order, according to my test light. Got a new board for the gauge cluster and a new headlight switch to be on the safe side, but so far, they haven't helped either.

MrAMC- The orange "hot" wire coming off of the headlight switch has a good connection, according to the test light. In theory, I should at least have the green lights behind the headlight and wiper switches (would it be possible that they wouldn't work because their grounding points are bad? The clock in the dash is missing because it's not functioning, was going to put a tach there in the future. I'm sure I could rig up a ground wire pretty quick). Still doing yoga trying to get under the rest of the dash to check the other wires further down the system. The orange lead going into the gauge cluster provides power for the setup there, correct? Been trying to decipher the electrical wiring diagram, but still a bit lost.

Bigbad69- Thought of that before, got a new headlight switch from APD just to be on the safe side. Still in the same situation before; headlights work fine, but the gauge cluster still won't illuminate.

Not sure what all to make of it myself. To my (limited) knowledge of electricity, hot wire + ground = shiny lights (assuming, of course, there's enough power). Would it be possible the voltage regulator would be shot, or would that make all of the lights go haywire?

Appreciate all the help, everyone, apologies again for the delay. Fall is always a busy time, even when social distancing is involved. Should hopefully have some more time this week to keep cracking on it, though, fingers crossed!

Cheers!
-Brad L.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote george w Quote  Post ReplyReply Direct Link To This Post Posted: Oct/24/2020 at 6:49pm
Voltage regulator is not the issue. If your headlights and tailights work then you have main 12v power going to the headlight switch's power input terminals marked B1 & B2. B2 is fused power coming from the fuse block. B1 is unfused and feeds just the headlights.
Do you have 12 volts at the orange wire on the headlight switch connector with the orange wire and on the other end that goes to the round female connector that plugs into the back of the instrument cluster. The headlight switch must be on of course and the headlight dimmer rotated fully CCW just before the detent ? If you do then you'll need to check the black ground wire pin connection on the cluster and the harness plug to insure it goes to ground.
The pins on the cluster PC board are numbered like the hours on a clock face. The index notch on the plug is at 12:00 and that's pin # 1. Dash lights, orange wire, is pin # 2. The black, ground return is pin # 5

I'm not sure where the ground return path is for the lights that illuminate the wiper and headlight switch bezels. You'll need to check behind the dash to see how those bulb sockets get grounded. I have a 69 AMX and it does not have lights for those controls. The clock ( or separate tach ) gets grounded through a simple flat copper piece that slips under the upper left mounting ear of the instrument cluster and under the right mounting ear of the tach or clock housing. Note that the back side of that upper left mounting ear of the instrument cluster must be clean and free of paint so the copper strip can make good contact.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mramc Quote  Post ReplyReply Direct Link To This Post Posted: Oct/26/2020 at 3:30pm
Brad I've got similar problem with my 1969 Javelin and I've not got them all figured out either. But I'll pass on a tip I got from a Mopar Magazine recently, as the period Mopar instrument clusters are almost the same as the ones uses on AMCs, check the small nuts on the back of the instrument cluster. According to the Mopars guys if the nuts are loose on the instrument cluster that cause the lights fickler or go out also. LRDaum  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote S Curry Quote  Post ReplyReply Direct Link To This Post Posted: Oct/26/2020 at 5:35pm
On the wiper, light switch dash light not working I believe a ground plate must be in place that the both switches go through and make contact with to complete the circuit. The dash is plastic.I think that a ground wire is connected to this plate. It's been over five years since I had mine apart. That plate some gets "lost". Or it could be the light switch itself. I know I had to replace mine as it was giving me fits...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote troutwilly Quote  Post ReplyReply Direct Link To This Post Posted: Oct/26/2020 at 9:38pm
An orange wire powers the wiper switch light, headlight switch light, a/c-heater control panel light, clock light, radio light, gear indicator light, and gauge cluster lights (all variable intensity).  It is connected to the "I" (Instrument) terminal on the headlight switch.

A red wire powers the map light, courtesy lights, and console (?) light (all non-variable intensity).  It is connected to the "Courtesy" tab on the fuse panel.

The ground plate (S.Curry) for the wiper and headlight switches also mounts the bulbs for those switches, and is grounded through its contact with the headlight switch (there is a tab sticking out the lower back of the headlight switch for a ground wire, make sure its there). This plate also provides the ground for the heater control panel light.

The copper tab at the top left of the gauge cluster provides the ground for the clock and its light.  I believe the ground for the gauge cluster is through the cluster connector black wire.

The map and console lights have their own grounds.  Courtesy lights are grounded through the door switches and/or the headlight switch when the knob is twisted all the way CCW.

Is your gauge cluster removable (woodgrain cover off)?  If so, check the connector for variable power at the orange connector and ground at the ground (black) connector.  Check for continuity between the connector on the cluster for those 2 locations to the bulbs (difficult to do with cluster installed).  And check for power to the other bulbs and continuity in the grounds.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FreeMoCo2009 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/27/2020 at 10:23pm
Update 2:

Hello everyone and thank you for the tips! So far been diagnosing every light using the advise here, one piece at a time. Got everything working with the exception of the gauge cluster. What I've found so far...

-Everyone is correct so far about the grounding locations for the wiper and headlight indicator bulbs: turns out the bulbs themselves were bad, but I had some spares off of a spare dashboard for the car. They're working beautifully now.
-The center console and map lights were removed and checked by themselves. Turns out the problem was just dirt on the contacts preventing a good connection. A simple scrub with a brass wire brush got both of the lights working just fine, and they've since been reinstalled.
-Bulb in the shift light and AC control lights are blown. Going to stop by the local auto parts store tomorrow and see if I can nab some, if not, then it's to the wonderful world of the internet to source some.

According to what I can diagnose, the gauge cluster gets both its own power and ground through the wires in the circular connector in the back. Been checking the circuit with my test light and volt meter, but so far, I'm still a bit stuck. Light says both the ground connection and hot wire are good, but the cluster still refuses to light. Also determined I'm getting voltage there (Gonna have to re-perform this test to make sure my volt meter isn't goofing up. Current meter I'm using works, but isn't the same as my old one, which seems to have grown legs and run away lol).

The confusing part (to me at least) is that the orange "hot" wires under the dash all have power. I now have light in all the accessories they hook up to, which is supposed to include the gauge cluster, as they're all spliced into the same bundle (or at least from what I can determine in the schematic of the car's wiring). Gonna try again tomorrow with the nut trick (Thanks MrAMC!) and report back when I can.

Big thanks again to everyone that's assisted so far, it's been a big help!

Cheers!
-Brad L.
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