Dash Printed Circuit Replacement Issue

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BSC73

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May 7, 2022
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My Car
1973 Fastback Mustang Mach 1 351Q 4v
Hello everyone, a little background information I currently own a 1973 Mustang Mach 1 351 Cleveland 4v Q code.

I recently replaced the printed circuit dash gauge on my mustang with a new replacement off of NPD which I will link to at the end. I also took the opportunity to replace my gauge lights since I pulled the dash out and used a led kit from NPD, which I will also link. When I went to check the lights by reconnecting the dash, none worked except for the turn signal lights. Does anyone know what might be the issue? Any suggestions are appreciated greatly, thanks.


Links:
 

DaveMT

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Gibsonia, PA
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1973 Mach-1 Sportsroof (1970, 351C-4V M-Code Motor, 4-Speed Toploader)
You can hook up each one of the LED Bulbs to a 9-Volt battery to test them. The attached diagram shows which side of the bulb needs to be connected to positive 12-Volts.
 

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  • 1973 Mustang Gauge Cluster Circuit Board Diagram.jpg
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DSwan

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You can hook up each one of the LED Bulbs to a 9-Volt battery to test them. The attached diagram shows which side of the bulb needs to be connected to positive 12-Volts.
I tested my cluster lights on the bench using a 9-volt after installing led bulbs as you outline. It worked great and kept me from having to r&r the cluster several times.
 
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My all time favorite vehicle is our 1969 Shelby GT500
I tested my cluster lights on the bench using a 9-volt after installing led bulbs as you outline. It worked great and kept me from having to r&r the cluster several times.
Thank you for sharing the results of the suggestion from DaveMT. It looked like a solid suggestion. Good to know you concur.
 
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1973 Mach 1 FI
Hi
VX7805-1000 ( cui from digikey 102-4253-ND)
inserted inside old metal regulator shell is an upgrade to all of your instruments. You have to ground terminal 2 to case ,Terminal one is input and 3 is output. You will get 5v fixed short circuit proof dead on. The fuel gauge should be recalibrated with an 11 ohm resistor for full tank and 75 for empty. You realy only need to do full if it worked before. Below is older regulator on back of instument panel and a Gauge from rear. The one that goes to fuel gauge is the output. The Gauge is showing high adjust and the one on right is zero.
 

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