I have been doing a little testing to see why my gauge light bulbs are not working. This is on my 1971 F250 pickup. Want to make sure I am heading in right direction before I move on to phase two testing. As a side note the gas, water. oil pressure gauges all work, Amp gauge does not.

Please look over the drawing and let me know if I am heading right. Any & all information will be of help, I have tuff/old skin. This truck is all new to me as I picked it up a few months ago and I am working on fixing the small things.

The three 2 amp fuses shown are for information only. I know there is only one in the fuse box.

 

Here you go for reference:

1972 Ford Truck Wiring Diagrams - FORDification.com

 

RichS2659 --- Thanks for the 1972 wiring diagrams. In going through the section on plate 5 it shows that all power to the the "Cluster Illumination Bulbs" goes through the 2 amp fuse first. From my drawing and this diagram I feel I am correct that the problem is between the 2 amp fuse output side and the cluster illumination bulb + side. Also from the diagram I need to make sure the cluster is grounded good.

One additional question, What is Model 84 that is called out with the "Cluster Illumination drawing"? It says one drawing is for all cluster illumination except model 84 & the other is for model 84 only?

It looks like I will have to remove the gauge panel so I can try a 12 volt jumper from the 2 amp fuse discharge side to the cluster illumination input to see if the factory 12 volt input wire is bad.

 

Have you already replaced the light switch itself? Have you checked the dimmer on the ****? The cluster grounds through the connector and to a chassis ground, could start by finding that ground and making sure it is connected to something solid. Since you would need to be behind the cluster anyway, you can take it out and check the printed flex board for cracks or breaks. and check all your bulbs again. Maybe they are shorting out/blown.

 

mchandford71360 -- Thanks for the additional information. I have not done any thing with the dash lights yet. I have been installing a better/brighter head light system in the truck.

Maybe after the holidays I will dig into the dash light problem. I will for sure check all the item's you posted. As I have to get into the cluster to test everything I am going to install a new light switch while I'm in there.

 

 

mchandford71360 --- Thanks for the gauge bulb information. I see where you are coming from. When I get into working on the gauge bulb problem I will test all the bulbs first & I will install the new light switch so I know the dimmer for the bulbs is working. I have tested the in / out power flow through the fuse block and it is all good. I am hoping that the problem is the main light switch. That would be an easy fix.

Did you come up with a new style spade fuse box that can replace the original OEM box?

 

 

mchandford --- Be sure to let use know what you come up with for the fuse box. My alternator gauge is the only one that does not work, may be in the wiring, not sure, tested the alternator output and it was fine. I have been told that I can test the gauge with a 9 volt battery just to see if the gauge has any movement when I have the dash cluster out.

 

A quick question on my dash gauge cluster light bulbs. If the system was working correctly will the gauge bulbs be on when you pull the light switch *** out half way (for running lights only) or does the switch have to be pulled full on?

This is on a 1971 F250

 

The dash lights come on with the running lights on my '70 F100. Hope that helps.

 

Ghill70 -- thanks for the reply, I am sure the 71 F250 is the same.

 

I know I may have asked this question before but I want to make sure before I dig into the dash light cluster. Does the 12 volt feed from the light switch go to the 2 amp gauge light fuse, then out of the fuse to the gauge light bulb?

 

 

The light switch has an automatic resetting, circuit breaker inside.