Circuit 19 - Dash Lights

[Nutinbutford]

I have no power to Circuit 19, Dash lights. Fuse is good, there's power through the headlight switch. It was working fine yesterday. All other dash stuff is fine, radio, wipers, lighter etc.

So, what have I done? I replaced the headlight switch, and lighter. I put new bulbs in all of the dash components. I reinstalled the gauge cluster and thought " should check things before going any further." Glad I did.

Any help would be awesome. Been at this all day about had plenty of character building.

Thanks,
Rick

 

[Don C]

Did you check for voltage on both ends of the fuse (fuse #3)?

 

[Nutinbutford]

Found the issue, I pulled the fuse from F5, found it was oxidized on the end furthest from the firewall. Changed it out all is good. Thanks so much Don and Ken, your questions got me to take another look at the fuse.

 

[Don C]

According to the wiring manual the fuse for the instrument/panel lights is #3. Make sure you have voltage on both contacts on that fuse when the headlights are turned on and the knob rotated to full brightness.
Fuse 5 should be for the heater/a.c.

 

[Nutinbutford]

Appears the panel for our '73 is different than the '71. Shows the F5 circuit is the instrument panel fuse.

 

[Hemikiller]

Appears the panel for our '73 is different than the '71. Shows the F5 circuit is the instrument panel fuse.

It's the same box and fuse location, they're just labelled differently in the drawings.

 

[GERMYS_72]

According to the wiring manual the fuse for the instrument/panel lights is #3. Make sure you have voltage on both contacts on that fuse when the headlights are turned on and the knob rotated to full brightness.
Fuse 5 should be for the heater/a.c.
View attachment 89509

Don,

I'm having same issue. Headlights are working, and headlight is turned all the way to the right.

I'm getting No lights to the Cluster (except turn signals and the red mustang light)


I am definitely not getting 12v to either side of Fuse 3 at the panel. I am getting 12v to both sides of the Horn fuse.

Does this sound like the headlight switch is the issue ?

 

[Don C]

Yes, or a bad connection

 

[Nutinbutford]

Could be the headlight switch. My issue was some oxidation on one end of the fuse. Took it out, cleaned it and all was good. Ended up putting a new one in just to be sure.

On a 73 there is a purple/white wire that provides 12 volt to the cluster. Also, there’s a ground lead from the lighter circuit…maybe check that.

 

[midlife]

Could be the headlight switch. My issue was some oxidation on one end of the fuse. Took it out, cleaned it and all was good. Ended up putting a new one in just to be sure.

On a 73 there is a purple/white wire that provides 12 volt to the cluster. Also, there’s a ground lead from the lighter circuit…maybe check that.

That purple-white wire is part of the brake proportioning valve system and has nothing to do with the dash lamps.

 

[Nutinbutford]

Hmmm…. Better check my schematic again, may have mis spoke…thanks Midlife.

 

[GERMYS_72]

thanks @Don C @Nutinbutford and @midlife

I'm going to change out the headlight switch today and see how that goes.

 

[GERMYS_72]

check out my old headlight switch I pulled today View attachment HL.jpg

I got the new headlight switch same day from Oreilly's.

Installed the new headlight switch.

I am definitely now getting 12v on both sides of the #3 fuse, but still no cluster lights
(except the turn signals and red mustang horse light)

Cluster circuit board is brand new from JEGS, cluster Voltage regulator is brand new, all sockets were cleaned with wire brush and contact cleaner, and every 194 bulb was tested for continuity and resistance.

Any other ideas on what else it could be ?

 

[GERMYS_72]

check out my old headlight switch I pulled today View attachment 90800

I got the new headlight switch same day from Oreilly's.

Installed the new headlight switch.

I am definitely now getting 12v on both sides of the #3 fuse, but still no cluster lights
(except the turn signals and red mustang horse light)

Cluster circuit board is brand new from JEGS, cluster Voltage regulator is brand new, all sockets were cleaned with wire brush and contact cleaner, and every 194 bulb was tested for continuity and resistance.

Any other ideas on what else it could be ?View attachment HL.jpg

 

[midlife]

Stupid possibility: you are pulling out the headlight knob to engage the cluster lamps, and then rotating the knob? Best to check for lamp illumination in a dark garage...

 

[GERMYS_72]

Stupid possibility: you are pulling out the headlight knob to engage the cluster lamps, and then rotating the knob? Best to check for lamp illumination in a dark garage...

yea Midlife, case closed. Thanks

In a pitch black garage I do see the cluster lights now. Very dim, but I'll maybe get some LED's later

Thanks again for everyone's help, the headlight switch replacement was the fix.