Instrument Cluster wiring Diagram

[1969 Project]

I finally pulled the trigger on a classic instrument gauge package. Does anyone have a basic wiring diagram of the instrument cluster? I only have the two gauges (MPH & Fuel).

[franken]

Maybe see the wiring diagram here. http://67-72chevytrucks.com/vboard/f...splay.php?f=64

[VetteVet]

Here is the cluster plug.








Here is the gauge wiring.

[1969 Project]

Just what i needed, thank you sir!

[RichardJ]

If his old dash has the warning lights, the wiring is going to look more like this. The full wiring from the links franken posted will have to be followed to get the full picture.

[VetteVet]

Yes Richard is right, if you had the light cluster you will have to make some wiring changes.
You will also have to get a different sensor for the temperature gauge since it is not a light anymore. You will also have to add the ammeter (battery gauge) wires and fuses.
Post back and let us know and we will guide you through it.

[1969 Project]

I did not originally have a temp, battery or oil pressure sensor in the truck but I installed some aftermarket ones. The gauges I ordered as a kit and comes with all new sensors (electrical). How would I have to wire the new sensors being that i never had them stock? My expertise is definitely not with electrical.

[1969 Project]

Can anyone explain why there are two green wires for the temp gauge lamp in pin 5? I am installing an electronic temp sensor for my new gauges and was wondering if these wires will be needed or if I can just exclude them from my new harness. Also will the two tan wires in pin 2 be needed for my new gauges/harness?

[VetteVet]

Well I think I can. LOL.
When the factory installed the light cluster they needed some way to test the warning light bulbs in the cluster. The wires on 5 and 2 are for the sending units on the temperature lights Pin 5, and the brake warning light, pin 2. The sending units are variable resistors to ground that will ground the warning lights when the sender resistor reaches a low enough resistance for the light to ground and turn on. In the case of the temperature sender, it grounds when the engine overheats.

The brake warning light is grounded by the switch in the brake combining valve by the master cylinder, when the brake pressure becomes unequal between the front and rear brake systems, usually caused by loss of fluid in one of the systems.

The extra wire in 2 and 5 are just bypasses direct to ground to turn on the lights to check them. This is done when the key switch is turned to the start position and the wires are grounded by the key switch through a separate connection in the switch.

Most of the harnesses are wired with the two wires at the key switch instead of the cluster plug but the effect is the same. If you were to turn on the key switch and ground the wires at the sender the lights should come on.

My 'question for you is--- have you checked the new cluster to match the pins where the plug goes with the copper strips to the gauges. I think you are aware that the aftermarket sensors have to match the gauges that they go to. If it's like the normal conversion from stock light clusters to gauge clusters that many of us have done then all you need to do is change the cluster plug wiring around and change the temperature gauge sender, or in your case the aftermarket senders. For instance the oil sender wire on pin 1 may go somewhere else if you have an electrical sender instead of the mechanical tube that the gauge cluster uses.
Another example is what about the battery gauge or are you getting a voltmeter?
This would change the wiring to pins 1 and 12 on the plug.

[1969 Project]

Thanks for the detailed info, much appreciated!
I got all my gauges wired up last night and all seems to work except the gauge lights. I hooked up both of the grey wires and my heater lamp comes on with the lights but no cluster lights, any idea on what could be the cause? I also checked fuses and they are all good.

[davepl]

Why is the warning light dash different than the idiot light dash? Is it something to do with the bulb test circuit? I can't figure out why, instead of sending binary on/off signals on the sensor lines (ground present or not) for the idiot light dash, they don't just send a variable signal (resistance to ground showing temp or pressure).

So the sender and the gauge change, but why did they HAVE to change the wiring between them? GM was not big on wasting money...

[VetteVet]

Originally Posted by davepl

Why is the warning light dash different than the idiot light dash? Is it something to do with the bulb test circuit? I can't figure out why, instead of sending binary on/off signals on the sensor lines (ground present or not) for the idiot light dash, they don't just send a variable signal (resistance to ground showing temp or pressure).

So the sender and the gauge change, but why did they HAVE to change the wiring between them? GM was not big on wasting money...

The warning light dash is the same thing as the idiot light dash, the idiot light dash is just a slang term given to the light dash. Why I don't know.

The normal operation of the temp warning and the charging light is just as you described where the variable resistance to ground makes the light come on dim to bright as the resistance decreases. AKA as the test circuit.

The gauge does not require the extra wire to test it so less wires needed.

the brake warning is just on/off with the switch in the prop valve.

If you saw my post above, the green and brown wires are your binary switching wires from on to off to check the light bulbs. They bypass the sensors directly to ground to turn on the lights when the key is on to the start position.

The gauges were added so that the operator could read the severity of the condition instead of looking at the light bulb and guessing.

HTH VV.

[guitardude127]

Originally Posted by VetteVet

Here is the cluster plug.



Attachment 1805560




Here is the gauge wiring.




Attachment 1805561

69C25 here. I'm needing help with the two fuel pins, the 20T and the 20P. I'm rewiring my truck and have come to this point, and only have 1 fuel wire with my painless kit that is a 20P. What is the purpose of that "feed" wire vs. "fuel guage" wire? Are both needed? Do I need to run a separate wire somewhere?

[dmjlambert]

20P "feed" wire provides 12V to power the fuel gauge, temperature gauge, temperature light, and brake warning light. It's just a power feed wire. 20T is from the sender in the gas tank. It provides a variable amount of resistance to ground, 0 to 90 ohms, and that is what makes the gauge move in response to different amounts of fuel.

[Black Diamond Dave]

Thanks! Still helping people many years later.