Swapping a Cluster

[CanuckTruck]

I have an 85 Sierra that currently has the dummy warning lights that I plan to swap out with a full cluster. I have read about needing the schematics in order to know which wire to move but how do I know what schematic I need?

Any advice appreciated

 

[Matthew C]

Here is some information I found useful while doing a cluster swap on my 87. I was able to combine these to figure out what everything did, as some stuff differs with the years.
I hope this helps.
-Matt

 

[CanuckTruck]

Wow! This is very helpful Matt! I’m going to use all of this. I’m curious if you know if the same wire that controlled the dummy light for temp as an example will now control the temp gauge. Or if I need to do something to change it from a dummy light to an actual gauge.

Thank you again! I appreciate this!

 

[Matthew C]

Wow! This is very helpful Matt! I’m going to use all of this. I’m curious if you know if the same wire that controlled the dummy light for temp as an example will now control the temp gauge. Or if I need to do something to change it from a dummy light to an actual gauge.

Thank you again! I appreciate this!

I would think it would work because the old sender on my full cluster had a single wire, which is a signal wire. If it's the same wire that runs from your coolant temp sender, I believe it would work.

 

[CanuckTruck]

Thank you for your insights! I greatly appreciate it!

 

[Matthew C]

Thank you for your insights! I greatly appreciate it!

No problem. Good luck with your cluster

 

[CanuckTruck]

So I am struggling to figure this out. My problem is that I don't know with 100% certainty what year the new replacement cluster came from and therefore don't know what changes I need to make to the wiring harness. Attached is a picture of both clusters. The top cluster is the new one and the bottom cluster in the photo is the old one with the dummy gauges. I assume it is wishful thinking to think that I can plug the harness in and that it would work but I don't know how to find out what I need to change. I don't even know if the cluster that was in there is the original either so I guess I am asking how to find out what schematic is the right one for each of these clusters? Anyone have any advice?

And is there risk of frying it if i try to plug it in to see if by chance it works? Bad idea?

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[Snoots]

Yes. There is a risk of frying it.

 

[CanuckTruck]

Okay good to know.

 

[Big Ray]

Are the sensors in the truck?
I'll find a schematic for ya.

 

[Big Ray]

Here you go...this is suppose to be for 81-87. I recently added a tach to my 79, so I've been in wiring mode lately.

Instrument wiring 1

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Instrument wiring 2

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[Big Ray]

In case you need more info...

Complete 73-87 Wiring Diagrams

Complete 73-87 Wiring Diagrams

forum.73-87chevytrucks.com

 

[Turbo4whl]

With both clusters, you can just trace the printed circuit board and see which wire goes where. Using the wire diagrams that both @Matthew C and @Big Ray posted plus your printed circuits you can see where each wire needs to be.

You will need to replace the temperature light switch (sensor) and the oil pressure switch with gauge sensors.
Remember your truck has two oil pressure switches, one for the pressure light or gauge, the other one for the electric choke. The choke has two wires.

 

[CanuckTruck]

Thank you for the input! I think this is a bit over my head but I am going to try to figure it out.

 

[Big Ray]

Post if you have questions. You can do this.