1969 F100 Instrument Cluster Lights not working, getting half power to the fuse box

[Cmd314]

Hey guys I'm working on a friends 69 f100 and the instrument cluster lights don't work. I took the old cluster and gauges out and installed an aftermarket setup. I tested a few days ago and it worked great. I attached the terminal from the alternator to the postive terminal of the starter relay and it seemed like some wires were crossed or something. But the issue is I'm getting power to one side of the 2amp fuse that controls the instrument cluster/ lighter/heater light etc.i looked from the cluster to the fuse box, the wire is intact and fine. the side from the headlight switch has power. So what do I do? Kinda lost. I have the wiring diagram right here it looks like the power comes from the headlight switch and isn't it supposed to put power to both sides of the fuse? Any help will be appreciated thanks.

[Ranchero50]

What does the alternator wiring have to do with the lamp problem?

Cluster lamp power goes through the dimmer coil on the back of the light switch. Check voltages from the battery ground through the switch to source your problems. Don't overlook any chassis grounds.

[Cmd314]

I'm getting power to the switch and I mentioned the alternator wiring because I hooked it up the postive side of the starter relay and when I put the battery terminals back on a bigger than normal spark occurred making me think maybe something shorted.

[Ranchero50]

Are you getting a full 12 vdc to the switch and reduced voltage out of it or?

Big spark usually fries the diode pack in the alternator. Is it charging correctly?

[Cmd314]

I'm getting a full voltage to headlight switch and the same reading when I measure the left side of the fuse . No reading on the right side of the fuse. Brand new fuse. And the alternator doesn't matter right now, we're installing a new one, we just got the truck back from paint and we're putting it back together. If it worked a week ago why isn't it working now?

[Ranchero50]

Which diagram are you using?

http://fordification.com/tech/schematics_h.htm

[Cmd314]

http://fordification.com/tech/wiring/69 ... s81-85.jpg

[Cmd314]

So in the wiring diagram the 19 wire is the one with the issue. I checked for power at the 25 wire and I get it at the headlight switch and the cluster fuse on the left side of the fuse. But the 19 going from the fuse box to the cluster has no power which means no lights.

[Cmd314]

And another thing I saw was referring to the wiring diagram is if you look at the headlight switch the A terminal has no wire going to it in this truck, is this normal or does there need to be one?

[Ranchero50]

#19 12vdc is good from the switch but the other 19's are dead? Only thing left is the fuse or it's terminals.

[Cmd314]

I just bought more fuses to see -and no luck same problem. I tried different amp fuses, nothing. The power is transferred through the fuse to the other side correct? This literally worked a week ago and nothing was messed with. How can I check if it's the bulbs in the gauges? But that wouldn't explain the no power issue. I'm lost and frustrated.

[Cmd314]

I cleaned up the terminals the best I could. It's original wiring and fuse box. But no luck, and I did that hours ago. I don't know where to go from here. As soon as I connect the fuse It should transfer power to the other terminal right? Which would give me lights to the instrument cluster correct?

[Ranchero50]

Yep. Turn the lamps on and with the fuse pulled check the voltage across the terminals. That will prove out the circuit. No voltage, you have a break in the current path other than the missing fuse. Voltage means the supply and ground paths are good and the problem is in the fuse connection.

Trust nothing, verify everything.

[Cmd314]

Do you mean putting the multimeter pos on one terminal and neg on the other terminal? or putting the pos to one terminal and the neg to sheet metal? and check both terminals like that? I did both of these and i got the same results 12.5v.

[Ranchero50]

Yep, that proves your circuit is good other than the fuse. If you find the voltage to ground drops with the fuse in, the fault will be between where you have voltage and where it is gone. In this case it still sounds like you have a fuse holder / fuse connectivity problem. Use a paper clip or something similar to jump them out and see if the lamps light.