Inst warning lights vs Gages 1976 C10

[ColChish]

I have a 76 c10 with inst warning lights. Want to replace them with a gage cluster (Temp,Oil,Volt, Clock). The cluster group has its own circut board. Before I start taking it apart, I would like to know what problems I may encounter in this swap out?

[ray_mcavoy]

Welcome!

Since you have a truck that's currently wired for a warning light cluster, you'll have to re-pin the cluster connector so it matches the pin-out of the gauge cluster printed circuit.

You can find the cluster pin-outs in the factory wiring diagrams that hatzie scanned & posted here --> http://67-72chevytrucks.com/vboard/s...d.php?t=545416
And here is another post with a chart that shows all of the 73-87 cluster pin-outs --> http://67-72chevytrucks.com/vboard/s...d.php?t=456877

In addition to re-pinning the cluster connector, you'll also have to:

(1) Swap the temperature light switch for a sending unit that will work with the gauge.
(2) Add a section of copper tubing for the oil pressure gauge (if you are using a 76 or 77 gauge cluster with a mechanical oil gauge).
(3) Or add a wire and oil pressure sending unit (if you are installing a 78+ gauge cluster with an electric oil gauge).
(4) Add a resistance wire or resistor for the alternator exciter circuit. That circuit was originally run through the "GEN" bulb in the warning light cluster. Trucks that were factory equipped with a gauge cluster used a section of 2Ω per foot resistance wire about 5 feet long (about 10Ω total). There are several options to deal with this (1) salvage the resistance wire from a junked truck with gauges, (2) use a 10Ω resistor (needs to be a fairly high wattage resistor), or (3) wire in a socket & bulb so you'll still have a "GEN" light along with the gauge.
(5) Add the wires for the clock. It uses it's own separate 2-wire (power & ground) harness that plugs into the fuse box and grounds to the dash.

[hatzie]

The nice thing about the 76 idiot light harness is the oil pressure sender wire is already in the harness all the way from the engine to the instrument cluster plug. You just need to add the gauge sender and re-pin the oil light terminal to the oil gauge terminal position.

GM went from mechanical oil pressure gauge to electric in late 77. If you don't already have a cluster get a 78-80 with the electric oil pressure gauge. It'll be easier to retrofit.

There are four bulb positions in the large gauges. Two in the speedo and two in the fuel gauge. The two fuel gauge/Tach bulbs are in use Seatbelt and Brake. The two bulb positions in the speedometer will usually be unused in a 78+ cluster (the overlays will say Lock and Oil??). If you're clever you can cut the GEN lens to fit over the bulb position that you choose. I used em both for "Glow/Wait" and "Water In Fuel" lamps on my 76.

[ColChish]

Thanks for the information. This should put me well on my way to getting the truck they way I want it. One question....the gage panel I want to install is from a 1986 K10. I'm installing it into a 1976 C10. Could I just get a 1976 circut board and change it out on the 1986 gage panel?

[ray_mcavoy]

Originally Posted by ColChish

One question....the gage panel I want to install is from a 1986 K10. I'm installing it into a 1976 C10. Could I just get a 1976 circut board and change it out on the 1986 gage panel?

I suppose you could, but there wouldn't really be any benefit. The connector still needs to be re-pinned when going from warning lights to gauges no matter what year cluster or printed circuit you use.

In fact, swapping the printed circuit would actually make things more difficult because the 76 printed circuit won't have any traces to connect to the 86 cluster's electric oil gauge. Like hatzie pointed out earlier, the 78+ clusters are actually easier to retrofit into a truck that started off with warning lights because you can simply re-purpose the "oil" light wire for the electric oil gauge sending unit.

[motornut]

I changed idiots to gauges,in my 78.
the idiot light to gauges location changes too
I had to re-pin or move wires as some would be a dead short.
I reused my sender wire for both "temp and oil",just changed the senders.
You may need a light anyway for the charge/alt light,depending on your setup
idiot clusters are not built the same as gauges.
i think the later style temp gauges and senders are not the same.ohms and hole size.
don't forget to paint the inside white while it's apart too