Dash lights not coming on. Weird issue

[Rindelmach1 14]

At some point the dash lights stopped working on my 69 mustang mach 1.  Temp, Tach, Fuel, idiot lights and turn signals work.  I had a chance to remove my cluster and tested the lights by applying 12v from a batter to contacts on printed circuit board and they illuminate. I checked my fuse and it is not blow.  I can check with voltmeter but question is, what should the voltage reading be for dash lights?   I tested grounds and they work.  The voltage reading on the plug (pin#2 facing driver side) feeds dash lights and i get 6-7 volts. 

[Rindelmach1 14]

BTW - this is more of a sanity check.  I think they should be 12v with light switch dimmer all the way on but i only get 6.5v.  If i dim the light switch it will go down to 0.  

[Midlife 814]

Could  be a bad contact between dash cluster connector and circuit card; break in circuit card.  6V is reasonable voltage, but that depends upon position (rotation) of headlight switch.

Are you using LED lamps by any chance?  Many LEDs require proper polarity for them to work. 

[Mach1 Driver 560]

The path is from the rheostat on the light switch to the 4A fuse in the block, and then to all of these lights: ash tray, heater, radio, two clock lights and 8 dash lights. Put your voltmeter on an easy light to get to like the ash tray- it should be close to 12v with the brightness turned all the way up. If it isn't I would check for corroded terminals on the 4A fuse (Mid can help you with those). If you get 12v at the ashtray, but not on the dash, then like Mid suggests it must be the connector to the circuit board in the dash.

[Rindelmach1 14]

thanks for advise. Will tshoot tomorrow.  I am using LED but I made sure to test for +- and put them on correct position on the circuit board.  I also hit the circuit board with 12v once the lights were in position.  Now that I know the path from light switch, I can test at the fuse for 12v. BTW the ash tray, heater, radio, two clock lights are all out as well.  So now that kind of rules out the plug right?

[Midlife 814]

9 hours ago, Rindelmach1 said:

thanks for advise. Will tshoot tomorrow.  I am using LED but I made sure to test for +- and put them on correct position on the circuit board.  I also hit the circuit board with 12v once the lights were in position.  Now that I know the path from light switch, I can test at the fuse for 12v. BTW the ash tray, heater, radio, two clock lights are all out as well.  So now that kind of rules out the plug right?

Yes it does.  It points to the headlight to fusebox area as the problem.

[rmarks 20]

Could possibly be the headlight switch itself.

[Rindelmach1 14]

Since my radio, heater, ash tray and clock lights didnt work i suspected the fuse box.  turned out to be that.  I just stuck a probe on the fuse clips and got 12v and everything started working.  Pretty strange but i guess bad connection. thanks for all the help.

[Midlife 814]

Ha!  I'm now 2 for 34,654 correct!  Getting better all the time!

[Rindelmach1 14]

I probably should really fix my fuse box.  there is a whire clipped to the front of the 14a (courtesy light, etc) fuse. And a jumper from that contact to the 20a (horn, etc) fuse. Midlife do you know which wire is the main 12v feeding the fuse?

[Midlife 814]

Main (battery power) is the middle two clips on the bottom row.  ACC power are the middle clips on the top row plus the odd clip just below those two.