Need help with cluster

[ethankane]

I am almost done with my 71 c10 after two years of work (with a lot of help reading this forum) I an getting the electrical back together inside. I installed the cluster and hooked it up.
All seemed good truck fired up headlights and dash lights work.
Only problems were
Fuel gauges pegged past full with only a couple gallons of gas.
Temp gauge pegged.
No temp light when the key is turned on.
So I read the forum grounded the bottom peg on the temp gauge still nothing there.
Ran entire new line to fuel tank because if I ground the line it worked. Still nothing.

Then I was testing the cluster with an electrical tester.
When I check the #2 wire on the plug there is barely any signal through the tester but the temp light comes on with the key on.
When I check #4 same dim light on tester and the fuel gauge works.
Then if I hit the top peg on the temp gauge same dim light and the needle moves on the gauge.

What an I missing. Any help is appreciated.
Thanks

[VetteVet]

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Originally Posted by ethankane

I am almost done with my 71 c10 after two years of work (with a lot of help reading this forum) I an getting the electrical back together inside. I installed the cluster and hooked it up.
All seemed good truck fired up headlights and dash lights work.
Only problems were

First of all let's establish whether you have a gauge dash or an idiot light dash.
Your post suggests that you have a light dash with an aftermarket temperature gauge.

Here is the connections for the gauge dash.






Here is the connections for the light dash at the cluster plug






The no. 2 terminal you're calling a temperature light is for the brake warning light on both types of dashes.
The temperature light is connected to terminal 5 on the light dash, and there is no connection to terminal 5 on the gauge dash. The temperature gauge sending wire is moved to terminal 6 on the gauge dash



Fuel gauges pegged past full with only a couple gallons of gas.


No connection to fuel sender in tank

Temp gauge pegged.

Gauge wire is grounded or wrong sender
No temp light when the key is turned on

You shouldn't have a temp light with a temperature gauge unless the gauge is aftermarket.

So I read the forum grounded the bottom peg on the temp gauge still nothing there.

Ground the wire from the sender to the gauge and the gauge should go to full hot. The bottom peg has to be grounded anyway, but to a good ground.

Ran entire new line to fuel tank because if I ground the line it worked. Still nothing.

Grounding the line puts the gauge to empty, so the gauge is working, you aren't getting signal from the fuel tank sender.

This wire runs from the no. 4 terminal on the gauge cluster plug to the fuse panel FUEL terminal, and then to the sender behind the seat. the terminal on the fuse panel is just a junction so you can run a wire directly to the tank from the no. 4 terminal, but first check to see if the tan wire is there that goes to the fuse panel. Do not put any voltage on this wire ever.

Then I was testing the cluster with an electrical tester.
When I check the #2 wire on the plug there is barely any signal through the tester but the temp light comes on with the key on.
It's the brake warning light and it should come on when the key is turned on, to test the bulb via the key switch.

When I check #4 same dim light on tester and the fuel gauge works.
Then if I hit the top peg on the temp gauge same dim light and the needle moves on the gauge.

You are probably grounding the gauges with the tester, and the readings are not accurate because they are not grounding through the senders.




Here is the diagram of the gauge cluster with the wire connections shown on the cluster plug. Notice the red dashed line on terminal 5 where there is no wire connected.








What an I missing. Any help is appreciated.
Thanks

[ethankane]

Ok I will keep at it. Thanks

[dmjlambert]

The only thing I would add is regarding "Fuel gauge pegged" is make sure your gas tank is grounded, or if plastic tank the sender metal should be grounded. If you recently painted and then put your tank in, you may not have a good bare metal connection where the tank is bolted inside the cab (or wherever it is).