68 Barracuda Instrument lights not working

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richangelo

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Just purchased a 68 Barracuda Convertible. Headlights work but no dash lights. Getting power on both sides of the fuse. Tried the dimmer on headlight switch but no lights. Car was restored 3 years ago. Guy who restored it said dash lights worked leaving his shop. Plug behind cluster appears tight. All gauges work. Blinker lights work. Any suggestions?
 
If the car wasn't being daily driven, the headlight switch can become corroded. You can try operating it again and again to try to clean the contacts (push/pull, twist/twist, over and over), or just buy a new switch.

The fact that the gauges work is great, and suggests the cluster plug is OK. Although every function is a separate pin, and any one pin could break loose at the solder connection to the circuit board. Let's hope it's not that.

If you have an inspection mirror on a stick, get a powerful light and see if you can inspect the wires leading into the plug. The individual wires end in copper connectors that just slide into the plastic plug — when reseating the plug, it is possible that one or more connectors doesn't seat — it just gets pushed out the back of the plug by the pin. This is obvious if you look at it.

You don't want to be pulling that whole plug if you don't have to — every time increases the chance of breaking a pin loose.

I would start with the headlight switch. You might also look at the hi-beam floor switch, and try the hazard switch to see if it works. It almost always has the corrosion issue since it is hardly ever used.
 
Check the electromechanical voltage regulator for the instruments, it's probably signed off this mortal coil.

Solid state replacements are available, and work MUCH better.

You know what? Ignore this post. I'm tarded and missed that it was the lights gone dead, not the instruments.

What MVH said.
 
I could be wrong here but are the taillights working? I always thought if your taillight fuse blows you lose the dash lights as well?
 
Is the wiring stock or OEM style replacement ( ie NOT "Painful", or "Should be EZ")

Are the bulbs incondescent?


Quick test...
If you rotate the headlight switch counter clockwise to the extream you should hear a click and the map/courtesy lights should come on, ( be sure the doors are closed) that should indicate the dimmer is in the full on position.
With the headlight switch pulled out at least 1 notch (parking lights) you should have dash lights

If no dash lights then a few things to check.

  1. Does the light in the radio work (assuming stock, indicates there is voltage to the orange feed for dash lights)
  2. Does the light in the gear indicator work (assuming stock, indicates there is voltage to the orange feed for dash lights)
  3. Do your temp and fuel gauges work? (Assuming stock, indicates the dash ground is functional)
  4. If the above work then it points to bulbs in the dash, or the wiring to the circuit board/s or the cir board/s or the bulb holders.
 
Kendog 170 said:
I could be wrong here but are the taillights working? I always thought if your taillight fuse blows you lose the dash lights as well
Click to expand...
Tan wire from light switch runs to fuse, then to orange wire to power the dash indicator and radio light.

Headlight switch gets power from main splice from alternator.

Headlights, brake lights, parking lights Dash lights and map / courtesy all get powered from that always on feed.
 
Dana67Dart said:
Is the wiring stock or OEM style replacement ( ie NOT "Painful", or "Should be EZ")

Are the bulbs incondescent?


Quick test...
If you rotate the headlight switch counter clockwise to the extream you should hear a click and the map/courtesy lights should come on, ( be sure the doors are closed) that should indicate the dimmer is in the full on position.
With the headlight switch pulled out at least 1 notch (parking lights) you should have dash lights

If no dash lights then a few things to check.

  1. Does the light in the radio work (assuming stock, indicates there is voltage to the orange feed for dash lights)
  2. Does the light in the gear indicator work (assuming stock, indicates there is voltage to the orange feed for dash lights)
  3. Do your temp and fuel gauges work? (Assuming stock, indicates the dash ground is functional)
  4. If the above work then it points to bulbs in the dash, or the wiring to the circuit board/s or the cir board/s or the bulb holders.
Click to expand...
Thanks.
Convertible so no interior light.
Radio works but aftermarket.
All gauges work.
I'm guessing stock bulbs.
Stock wiring.
Light in gear indicator not working but who knows if it should. Everything was disassembled with restorer.
 
mvh said:
If the car wasn't being daily driven, the headlight switch can become corroded. You can try operating it again and again to try to clean the contacts (push/pull, twist/twist, over and over), or just buy a new switch.

The fact that the gauges work is great, and suggests the cluster plug is OK. Although every function is a separate pin, and any one pin could break loose at the solder connection to the circuit board. Let's hope it's not that.

If you have an inspection mirror on a stick, get a powerful light and see if you can inspect the wires leading into the plug. The individual wires end in copper connectors that just slide into the plastic plug — when reseating the plug, it is possible that one or more connectors doesn't seat — it just gets pushed out the back of the plug by the pin. This is obvious if you look at it.

You don't want to be pulling that whole plug if you don't have to — every time increases the chance of breaking a pin loose.

I would start with the headlight switch. You might also look at the hi-beam floor switch, and try the hazard switch to see if it works. It almost always has the corrosion issue since it is hardly ever used.
Click to expand...
Thanks.
Headlight switch turns on headlights. High beam and flashers work.
 
The dash, shift indicator and radio light are controlled by a rehostat in the headlight switch. Red line.

Many times the sweep fails or the rehostat wire windings fail. That would be my guess as to the issue based on the info you provided. A bad connector could also be the issue.
Screenshot_20230410-204049.png
 
richangelo said:
Thanks.
Convertible so no interior light.
Radio works but aftermarket.
All gauges work.
I'm guessing stock bulbs.
Stock wiring.
Light in gear indicator not working but who knows if it should. Everything was disassembled with restorer.
Click to expand...
Vert has little round interior light fixtures at lower rear panels. Interior lights are not on the same orange wire/dimmable circuit so not relevant to your problem. Look at the switch in post #13. See the hole in one connector? Any conductor from a nail to a piece of household copper wire down through that hole to the connector directly below it at center of rheostat is a rheostat bypass. If everything else is good, you will have full on dash illumination.
The rally panel has 2 circuit boards, thus 2 connectors. Orange wire in each connector supplies 2 of the 4 illumination bulbs. The more common problem is 2 lights working on right side but 2 lights not working on left side. Reason being, that connector was placed too close to the top of the circuit board. The 3 pins there are easily damaged at panel removal.
 
A lot of excellent information in this thread.

If you have a multi-meter or test light, one approach is to test whether there is power present for the circuit at the fusebox.
The instrumentation, radio and gear selectot lights get power from the end fuse in the box. Its a 2 or 3 amp fuse.
The convertible interior lights always have power. They get power from a fuse shared with other lights such as rear lights.
Blinkers are not fused in '68 - seperate circuit.
Headlights are also seperate circuit - circuit breaker insight the switch.

The headlights switch is really a multifunction switch, with three circuits going through it.
1681221551217.png
 
Side note, Turn Signals are a switched 'Accessory'. They should only work when the key switch is turned to run or accessory positions.
upload_2021-8-3_18-40-48-png-png.png
 
Re. Mattax's excellent diagram, do the parking lights and headlights get power from the black wire? And if so, they are not fused?
And why not supply power to them via the pink, fused line? I can understand the headlights drawing too much power relative to the dash and dome lights, and needing a separate feed, but where's their fuse and parking light fuses? I'm in same dilemma, no dash or dome lights.
 
The headlight switch has two power feeds into it for lighting. One direct; the other through the fuse.
The headlights are protected by an internal 15 amp circuit breaker.
The parking lights are protected by the fuse.

Why are they seperate? Either to insure if the headlights short out, the parking lamps and tail lights still will work; Or because even the original 40 Watt headlamps will draw 8 to 9 amps all by themselves. Splitting the load keeps both wires cooler and less likely to fail.
 
Lets look at the fuse box from a '64 shop manual, removing the accessory that probably didn't come on your car.

1695423308280.png

Accessory feed Q2A is power through the key switch.
1695423385918.png

12 gage wire black.
Feeds three fuse slots.

Q3 come directly from the power circuit (battery and alternator) and is always hot if the battery is connected.
1695423462107.png

12 gage wire Red with stripe
Feeds two fuse slots.

One of these fuses protects the Dome, stop and tail light circuits.
If the diagram is to be beleived, these circuits are all spliced to wire M1.
1695423751215.png


1695423802790.png


1695423853255.png


1695423871911.png


Stop light circuit changes color after the switch on the brake pedal.
1695423899841.png



Dome light circuit wires change color after the dome light.
From M1 pink to yellow for returns M2.
1695424118798.png


Also Unlike 68 Barracuda, note the parking light circuit is connected to the headlight switch P terminal so they turn off when the headlights go on. Tail lights are on the R terminal, so they stay on.


But what you really need to do is look at what the non working circuits have in common.
Fuse is the first item they share. But they also share that with the stop light. If the stop light works, then the problem is after the stop light connection.

Its also possible there are two seperate failures.
 
Mattax said:
If the diagram is to be beleived, these circuits are all spliced to wire M1.
Click to expand...
If true, you'll find one wire (M1) at the fuse of your '64
1695424930935.png


However if you do, check the connection at the headlight switch's B2 terminal. Manufacturing may have found it more practical to join the wires at the terminal than make a welded splice in the middle of the wire.
 
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