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Instrument Panel Lighting

sdcbowler

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Hey there, Members

I am having an issue with my instrument lamps (’70 Challenger, Standard Gauges). The light bar, Console gear selector, and Heater switch lights refuse to come one. As a FYI, Dome, Door, and map lights are working.
When I put direct power to the orange wire at the ignition connector, all the light come on, but I don’t think the current is flowing thru the dimmer switch as turning the dimmer does not affect the brightness. Also:
-If I apply power to the fuse block on either side of the instrument lights circuit Double Orange or Tan side, the lights come on.

What I know/determined:
-Dimmer switch gets power from Head Light switch (BK Wire)
-I get nothing from the Tan wire in the Dimmer switch connector
-With the key on, with the head light switch in any position; I get no power at the fuse block in
The instrument lamps circuit.
-The Dimmer switch appears to be properly grounded. The main switch bracket for all the switches has continuity to ground. I check two locations on the dimmer bracket and it appears to be grounded. I removed the dimmer knob and the shaft had continuity to ground (don’t know if that should or should not be)



***My question is, if not from the fuse block (Instr Lmps Circuit), where does the orange wire get its power from?........or am I way off.
In the attached wiring diagram I can see the orange wire seems to originate from the ignition switch connector of the dash harness but there is no corresponding wire in the mating connector (refer to photo).

Any advice would be greatly appreciated
Thanks

IMG_20230503_163905565.jpg


IMG_20230430_113247426.jpg
 

pschlosser

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Maybe this is obvious, but my instrument panel dimmer knobs on e-bodies gone bye have been noisy and fraught with oxidation. Many had spots where the instrument panel was dimmed completely. I recommend you confirm the output on the instrument panel dimmer is on full.
 

Sinitro

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A simple FIX is to jumper the dash lite dimmer rheostadt, so that the 12V goes direct to the dash lites..
The dimmer rheostadts are 50 years old and typically are dirty with poor winding/contacts..

Just my $0.02...
 

sdcbowler

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Just looking at the switch, and the opoeration of other components on the circuit, I would imagine that:
-Bk/Y* is good since this is the same wire from my previous issue with the side marker lights, which are now operational
-BK wire is power input from the light switch
-The two yellow wires are for the map light/right door light and the dome light and the left door light, all of which are working properly
-This leaves the Tan wire to the fuse block where I get no current at all, which seems to be the culprit

Would you suggest I test the output of that wire? If so, How would you recommend I do it?

Thank you
 

sdcbowler

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A simple FIX is to jumper the dash lite dimmer rheostadt, so that the 12V goes direct to the dash lites..
The dimmer rheostadts are 50 years old and typically are dirty with poor winding/contacts..

Just my $0.02...
I thought about doing that, but wouldn't that mean the lights will be at full brightness everytime I turn the lights on?
 

72RoadRunnerGTX

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The illumination circuit is powered from the headlamp switch “R” terminal, black wire L7A-18BK to the dimmer rheostat, from there to the illumination fuse via tan wire E1-18T. From the fuse to the orange dash illumination bulbs. Verify you are getting power from the headlight switch. Also verify battery voltage is present on “B2” at the headlight switch, if not, check the “Tail Lamps” fuse. A ground at the dimmer switch is not necessary for illumination functions, only to turn on the dome lamps manually.

The orange wire at the ignition switch Molex is to support an auto column gear shift selector lamp if so equipped.
ebody dash lights.jpg
 
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tonysrt

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If your not getting power to the dash lights also check the dimmer switch because it has a brass arm that rides the rheostat that may have fallen off or not touching it. That brass arm is very thin.
 

sdcbowler

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The illumination circuit is powered from the headlamp switch “R” terminal, black wire L7A-18BK to the dimmer rheostat, from there to the illumination fuse via tan wire E1-18T. From the fuse to the orange dash illumination bulbs. Verify you are getting power from the headlight switch. Also verify battery voltage is present on “B2” at the headlight switch, if not, check the “Tail Lamps” fuse. A ground at the dimmer switch is not necessary for illumination functions, only to turn on the dome lamps manually.

The orange wire at the ignition switch Molex is to support an auto column gear shift selector lamp if so equipped.View attachment 106250
Thanx GTX. I will give this a try today. Come to think of it, I have never tried to turn the dome lamp on manually. I have always been standing outside the car reaching in through the window....lol
 

sdcbowler

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If your not getting power to the dash lights also check the dimmer switch because it has a brass arm that rides the rheostat that may have fallen off or not touching it. That brass arm is very thin.
Another good suggestion. This will be my 'If all else fails' test.:thumbsup:
 

sdcbowler

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***NEW UPDATE***

Ran a few tests and below are the results

1. When I attempt to turn on the dome light manually, it does not come on. In the dimmer switch, I cannot even feel the slight transition bump when going from max instrument illumination to turning on the dome light

2. Voltage into Dimmer Switch (BK wire)
Light switch in middle position: 11.8v
Light switch fully on (top position): 11.4v

3. Dimmer Connector attached to Dimmer, Light Switch on
Jumper between middle tab of dimmer (Tan wire)
-and Tan tab at Fuse Block (No fuse), has continuity: 0.0v
-and Tan tab at Fuse Block (Fuse added), has continuity: 0.0v
-and Orange tab at Fuse Block, same circuit (Fuse added), has continuity: 0.0v

4. Dimmer By-pass
Disconnected dimmer switch and added a jumper wire to dimmer connector at harness.
Jumper wire connected between BK (dimmer input) and Tan (dimmer output) wires
Turned light switch on and instrument lights also came on. Of course they don’t dim Since the dimmer is disconnected.

I am concluding the dimmer switch is no good, unless you all tell me there is something else I should look for.

Thanks
 

devinism

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***NEW UPDATE***

Ran a few tests and below are the results

1. When I attempt to turn on the dome light manually, it does not come on. In the dimmer switch, I cannot even feel the slight transition bump when going from max instrument illumination to turning on the dome light

2. Voltage into Dimmer Switch (BK wire)
Light switch in middle position: 11.8v
Light switch fully on (top position): 11.4v

3. Dimmer Connector attached to Dimmer, Light Switch on
Jumper between middle tab of dimmer (Tan wire)
-and Tan tab at Fuse Block (No fuse), has continuity: 0.0v
-and Tan tab at Fuse Block (Fuse added), has continuity: 0.0v
-and Orange tab at Fuse Block, same circuit (Fuse added), has continuity: 0.0v

4. Dimmer By-pass
Disconnected dimmer switch and added a jumper wire to dimmer connector at harness.
Jumper wire connected between BK (dimmer input) and Tan (dimmer output) wires
Turned light switch on and instrument lights also came on. Of course they don’t dim Since the dimmer is disconnected.

I am concluding the dimmer switch is no good, unless you all tell me there is something else I should look for.

Thanks
Dimmer switch is the culprit. Bypassing it verified that it is inop.

I have rebuilt hundreds of them.
 

mint33

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I’m looking for any input on installing a rebuilt dimmer switch into the dash while in the vehicle. Has this step by step process been posted before. Thanks
 

EW1BH27

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Remove the light bar first then the corner switch panel comes off by removing 4 screws.
 
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