Warning lights to gauges

[jdoisher]

I've done some searching and have not found a clear answer.
The truck came with a warning light cluster
I bought a gauge cluster (no tach) with the harness that attaches to it.
I also bought a engine harness for a gauge cluster.
What I dont have is a "cab" gauge harness.
My queston is that I would assume I'll need to add and or move some wires around, I havent had a chance to look at the truck so don't be to hard on me. Is there a step by step swap that I havent found? Any help would be much appreciated!
Its a 66 chevy truck.
Thanks Jason

[ray_mcavoy]

Hi Jason,

I wrote up a swap page back when I did this conversion in Dad's 66 --> http://rmcavoy.freeshell.org/Truck_gauges.html

It doesn't have a step by step of how to modify the harnesses yet but I have been working on a write-up that does. I haven't gotten around to uploading that yet so I'll post it here.

I see that you already have the cluster harness and engine harness so that's a good start. In addition to modifying the cab harness, you'll also have to make some minor changes to the headlight/alternator harness.

(1) The dark blue wire for the "OIL" light is no longer needed since the gauge is mechanical. You can leave that wire unused in the cab harness since it doesn't interfere with anything.

(2) The dark green wire that used to go to the "HOT" light can be re-used for the temp gauge sending unit. You can pretty much leave that wire as-is in the cab harness but it would be a good idea to remove the branch that goes to the ignition switch for the "bulb check" feature.

(3) The light green wire that used to go to the "COLD" light can be re-used as one leg of the ammeter (BATT gauge) circuit. It's already hooked up to the correct terminals in the cab harness and is the correct gauge ... only the color code is different ... factory gauge wiring used a black wire.

(4) The brown wire that used to go to the "GEN" light can be re-used as the other leg of the ammeter circuit. Again, it is already hooked up to the correct terminals and is the correct gauge ... only the color code is different ... factory used black with white stripe.

(5) The cab harness contains a resistance wire (brown with white stripe) that needs to be re-pinned to a different slot on the bulkhead connector. See the factory wiring diagrams that I have posted on my site in the above link. This wire also needs to be re-pinned on the headlight/alternator harness to match.

(6) The other leg of the ammeter wiring (black with white stripe) needs to be added to the headlight/alternator harness. It hooks to the junction point on the horn relay.

(7) I would highly recommend adding some inline 4 Amp fuses to the ammeter circuit just like GM did on the 67-72 trucks.

[jdoisher]

Thank you!! I will work on it next week and let you know how it works out!! I had already printed your thread out!! Again thank you!!
Jason

[jdoisher]

Looks like I have only one question and it pertains to number 5. What is it that I'm repining the brown wire white strip too? I've only looked at the wires on the cluster and the wires on the fire wall. I have pulled up a color diagram of the wire harness and clearly see it. What am I moving it to do is my question.
Thanks again
Jason

[ray_mcavoy]

Hi Jason,

Your existing warning light type cab harness should have that brown/white wire running from the ignition switch to one of the terminals on the driver side bulkhead connector. At the connector, it will be crimped into the same terminal as the solid brown wire that goes to the "GEN" light.

The re-pinning I mentioned in (5) involves separating those two wires by cutting the brown wire with the white stripe close to the bulkhead connector. Leave the solid brown wire attached to the terminal and leave the terminal in it's current slot in the connector housing.

Obtain some male and female Packard 56 series terminals ... they're available from NAPA and other places. Crimp one of those terminals onto the cut end of the brown/white wire. If I remember correctly, the cab side takes the female terminals.

The warning light type cab harness should also have one empty slot in the driver side bulkhead connector that's not currently occupied by a wire/terminal. Snap the newly crimped terminal on the brown/white wire into that slot.

That completes the modification on the cab harness. The solid brown wire will become one leg of the ammeter wiring. For reference, the factory used a black wire with a white stripe for this part of the circuit but it follows the same routing.

Now you need to do some re-pinning on the headlight/alternator harness that plugs into the under-hood side of the driver side bulkhead connector. That involves:

(1) Locate the brown wire that comes from the #4 terminal on the voltage regulator and remove it terminal and all from the bulkhead connector. The male Packard 56 terminals used here can be removed from the housing by squeezing them edge wise and carefully pulling on the wire. Re-form the terminal afterwards by spreading it apart a little with a narrow screwdriver in the terminal's center slot.

(2) The under-hood side of the driver side bulkhead connector will also have a single unused slot that corresponded to the unused slot on the cab harness. Take that brown wire/terminal removed from (1) and insert it into that previously unused slot.

(3) Crimp a male 56 series terminal onto a section of 20 gauge wire (factory used black w/white stripe) and insert it into the slot that was vacated by the brown wire removal in (1).

(4) Connect the other end of the 20ga wire added in (3) to the buss bar / junction on the horn relay. The buss bar / junction is the part with the 2 screw terminals. Hook it to either screw. Adding a 4A inline fuse to this wire near the horn relay end is highly recommended.

That'll complete the modification to the headlight/alternator harness.

One final note, you shouldn't have to re-pin anything on the cluster connector of the cab harness.

[jdoisher]

Got it 100% Thank you again very much!!
Jason

[Chevystep]

Read your excellent write up and been to your website as well for this gauge conversion. Going to do the same thing to my 66 with a gauge/tach cluster. I am starting from a warning light harness. Maybe I missed something after reading it a bunch of times, but what is the other wire connected to the two pronged temp gauge or is another wire needed? I'm also going to use the blue wire oil pressure sender bulb in the "T" arrangement you use and just have it light up the "overspeed" bulb location. Thanks for your help!

[ray_mcavoy]

Originally Posted by Chevystep

Read your excellent write up and been to your website as well for this gauge conversion. Going to do the same thing to my 66 with a gauge/tach cluster. I am starting from a warning light harness. Maybe I missed something after reading it a bunch of times, but what is the other wire connected to the two pronged temp gauge or is another wire needed?

The warning light cluster has both a "hot" and a "cold" light that are operated off the 2-prong temperature switch. The dark green wire (that originally went to the "hot" light) can be re-purposed as the sending unit wire for the temp gauge (which uses a single-prong sender) . The light green wire (that originally went to the "cold" light) is no longer needed.

If you compare the diagrams, you will notice that some of the connections for the "battery gauge" (ammeter) wiring in the gauge style harnesses pass through the same connector cavities that were used by that light green "cold" light wire in the warning light style harnesses. So that means you have a choice of (A) re-purposing that light green wire as one leg of the ammeter wiring by re-routing it down to the starter batt stud. Or (B) replacing it with a black wire (following the same routing) so it matches the factory color code. In either case, I recommend adding 4 amp inline fuses to both legs of the ammeter circuit (one in this black (or re-purposed light green) wire that connects to the starter batt stud, and another in the black w/white stripe wire that connects to the horn relay).

Originally Posted by Chevystep

I'm also going to use the blue wire oil pressure sender bulb in the "T" arrangement you use and just have it light up the "overspeed" bulb location. Thanks for your help!

Yes, that blue wire for the oil pressure light is otherwise unused with the gauge cluster so keeping it connected and re-purposing the "overspeed" light as an oil pressure light should work just fine. You could probably even make a replacement plastic lens/filter for that light that reads "oil" instead of overspeed.

[Chevystep]

AH....I went back and looked at wiring diags for a gauge truck and the "other" wire on the temp gauge is just one of the pink ones I already have...Thanks for the info and your great work/posts on this!

[Ken Cook]

I just started this cluster project but I have been looking at the diagram for a while now.

I used the light green wire from the cold side of the temp sender to run the gauge and hope to use the Hot Light (in cluster) in the lower left hole in the cluster, below the temp gauge, in the future maybe I can keep the hot light by some how using 2 sending units. For now I have the GEN Light there.

I placed the Oil Light in the lower Rt hole (overspeed) and plan to use a T in the future.

Keep in mind that I have a 63' 6cyl that came with the low end gauges and I am using all original harnesses.

1) the fuel gauge is on the same pins on both gauge and light cluster harnesses.
2) the oil gauge don't use any part of the harness
3) AMP GAUGE...I'm hoping to replace the amp gauge with a volt gauge. This will need a ground but I think I can just use the pink wire for the 12 volts.

That meant I didn't need to buy any of the 3 harnesses.

Just use the Hot or Cold Lights wires to run the temp gauge, the fuel gauge is already correct and I added 1 extra backing light that came from e-bay.