bench testing gauge lights

[ducky]

Hey all. Is there a good way to bench test to make sure all lights in the gauge pod are working? I just replaced all the light holders and lights, including turn signals, and just want to make sure they all have good continuity before putting into the truck. I tried reading the wiring diagram, and while I admittedly suck at that, I cannot tell where ground is. I tried just putting the negative lead on a 12v battery to the body of the cluster, and touching individual pins, but got nothing. No sparks either, so nothing should be cooked.

[datzenmike]

Dash illumination, on the 12 pin connector, connect power and ground to terminals 2 and 4. That's the Green/Black and the Green/Blue wires.

Keep ground in place...

Left turn #5

Right turn #3

 

Apply power to # 8

ground the following..

#7.... Brake

#6.... Charge

#12.. Oil

 

Power and ground to #10 and #11 for high Beam.

[ducky]

Thanks Mike! Another question is where would the blue wire coming from the top of the cluster go? I have a blue with white stripe that reaches, but my diagram says that’s the fuse on the cigarette lighter.

 

[datzenmike]

Blue wire is the tach signal from the coil negative terminal.

 

Blue/White is connected to an inline 15 amp fuse and to power from the main buss between fusible link and the ignition switch. It also powers the cigar lighter the clock and interior lamp. The inline fuse is taped up into the main harness behind the glove box area where it exits the cab for the engine bay

[ducky]

1 hour ago, datzenmike said:

Blue wire is the tach signal from the coil negative terminal.

 

Blue/White is connected to an inline 15 amp fuse and to power from the main buss between fusible link and the ignition switch. It also powers the cigar lighter the clock and interior lamp. The inline fuse is taped up into the main harness behind the glove box area where it exits the cab for the engine bay

so does that make sense for the blue wire from the cluster connecting to the blue and white one? Since I see no wire color labels on the diagram for the cluster itself, I can’t tell. It was actually taped off on the one I pulled from the truck

Edited November 16, 2024 by ducky

[datzenmike]

No sense at all. Already said this.

 

Blue goes straight to coil negative terminal and makes no other connection. It was taped off because you probably don't have the tach option. It's unused.

 

Blue/White has 12v on it to power the clock, interior light and the cigar lighter.

[ducky]

Yeah, unfortunately, if I had understood you the first time, I likely wouldn't have asked in a different way. I won't plug it in, though am still confused why it even exists. The blue wire from the gauges goes to the coil, apparently, even though they have nothing to do with the tach? The service manual for 1974 mentions attaching wires to various spots on the gauge pack that don't exist on any of the three I have.

 

I'll look to try and find threads on a tach install now, as I'm more curious than before. As for the bench testing of the turn signals, that did not work, though I did get them to light by applying negative to the side of the connector and positive to the spade connection, so hopefully they work properly when the harness is plugged in as intended.

[datzenmike]

I haven't seen what you have so by description it sounds like the tach signal wire. The coil sends a signal on that Blue wire to the tach. It's what the tach needs to read the engine RPMs. As I said if it it's not connected probably the truck didn't have that option installed.

 

My wiring diagram is very hard to read.