Stock Cluster to a Rally Gauge Cluster

Q: Stock Cluster to a Rally Gauge Cluster

Converting a Stock Cluster to a Rally Gauge Cluster on 1967 Firebirds.

By Tony and converted by Al

A: Introduction

For those who wish to convert their stock, (idiot lights) speedo cluster to a Rally Gauge Cluster, on their 1967 Firebirds, here is the background information you will need to accomplish this task. This information has been verified using two bone-stock 1967 Firebirds, one with a stock cluster, and one with a Rally Gauge Cluster.

Quick Facts

First, the Rally gauge cluster is NOT a drop in replacement for the idiot light cluster. The pin-out of the cluster connector is completely different between the two clusters.

Second, the Rally Gauge cluster uses two additional wires, (heavier gauge BLACK and WHITE wires), that are NOT in the standard idiot light cluster wiring harness. Therefore a simple re-pinning of the cluster connector and replacement of engine sending units will allow all BUT the voltage gauge to work.

Third, to make the generator gauge functional without replacing both the instrument panel harness and forward headlamp wiring harness, you will need to add two additional wires.

Stock Cluster Information

Let’s start out by looking at how the stock cluster works.

The stock cluster connects to the Firebird’s electrical system via a 12-pin connector. This connector has the pin numbers molded into the connector itself. The following diagram illustrates the pin-out of the connector for a stock cluster:

Connector pin ordering:
1——— 6
12 ——- 7

Idiot Lights (Stock Cluster)

Pin # Wire Color Usage
1 Light TAN Fuel Gauge
2 GREEN (2 wires) Water Temp Light
3 GRAY Illumination Lights
4 N/A
5 N/A
6 N/A
7 PINK (2 wires) Ground
8 BLUE/WHITE Stripe Oil Pressure Light
9 Light BLUE Left Turn Light
10 Dark TAN Brake Light
11 Brown Generator Light
12 Medium BLUE Right Turn Light

The TEMP, OIL, GEN, and BRAKE indicators in the stock cluster are used to notify the driver of a possible trouble condition under the hood of the car. The wires associated with those indicators on the stock cluster connector will get connected to wires located in either the “engine harness” or “forward lamp harness” under the hood of the car. These connections are made through two connectors on the firewall of the car.

Under the hood of a 1967 Firebird, on the firewall just below and to the right of the brake master cylinder, you will find two 10-pin connectors, with two wiring harnesses attached to them. When standing in front of the car facing the firewall, the connector on the left is the “Engine Harness” connector, and the connector on the right is the “forward Lamp Harness” connector. The following diagram shows the connector positions and wire colors associated with indicators on the stock cluster:

         Dark Tan -+  
                  |   
            +---+---+       +---+---+
            |   | * |       |   |   |
            +---+---+       +---+---+
            |   |   |       |   |   |
            +---+---+       +---+---+
Dark Green  | * |   |       |   |   |
            +---+---+       +---+---+
 Dark Blue  | * |   |       |   | * | Brown 
            +---+---+       +---+---+
            |   |   |     ( |   |   | 
            +---+---+       +---+---+


 +---+---+ +---+---+
 |      |  *  | Dark TAN  |     |     |
 +---+---+ +---+---+
 |      |      |  |     |     |
 +---+---+ +---+---+
Dark GREEN   |  *  |      |  |     |     |
 +---+---+ +---+---+
 Dark BLUE |  *  |     | |      | *  |  BROWN
 +---+---+ +---+---+
 |      |      |  |     |     |
 +---+---+ +---+---+

The Dark TAN wire connects to a pressure sensitive switch on the brake master cylinder. This wire gets connected to the Dark TAN wire of the Cluster connector and is used to turn on the BRAKE light if the line pressure in the master cylinder drops below a safe level, (indicating loss of fluid, internal seal failure, or open brake line.)

The Dark GREEN wire is connected to the coolant temperature switch located on the engine. This wire gets connected to one of the two GREEN wires of the Cluster connector and is used to turn on the TEMP light if the coolant temperature raises above 210 degrees, (indicating a possible overheating condition), (the second GREEN wire is connected to the ignition switch and I’ll explain why at the end of this section.)

The Dark BLUE wire is connected to the oil pressure switch located on the engine. This wire gets connected to the “BLUE with WHITE stripe” wire on the Cluster connector, and is used to turn on the OIL light if the oil pressure in the engine drops below a certain level.

The Brown wire is connected to the voltage regulator. This wire gets connected to the Brown wire of the Cluster connector and is used to turn on the GEN light if the output voltage of the alternator drops below a certain level indicating a possible alternator failure.

Earlier I mentioned that pin 2 of the stock cluster connector had two GREEN wires connected to it, one which went to the coolant temperature switch, and one which went to the ignition switch. The reason for the second GREEN wire to the TEMP light has to do with a courtesy that GM built into the stock cluster that most people do not realize. On all GM cars of that era, when you turn the ignition key to the “RUN” position, before starting the car, your OIL, and GEN indicators are supposed to illuminate so that you can verify that these indication circuits are functioning correctly. Without the engine running, the oil pressure should be at zero and hence the OIL indicator should illuminate. Without the engine running, the alternator is not turning, so the GEN indicator should illuminate. Under this condition, (ignition key in the RUN position and engine not running), you are able to verify that all the components of the GEN and OIL indication circuits are functional. However, the TEMP circuit is entirely different. Under normal conditions, the engine should never be in an overheated condition, so GM had to provide a “cheat”. When you turn the ignition key to the “START” position, the ignition switch illuminates the TEMP indicator to allow the driver to verify that the TEMP indicator bulb in the stock cluster is functional. However, it does NOT verify that the coolant temperature switch, or the wires connecting that switch to the stock cluster are functional, hence the “cheat” and the reason pin 2 of the cluster connector has two GREEN wires.

RALLY Gauge Cluster Information

The Rally Gauge cluster connects to the Firebird’s electrical system via a 12-pin connector. This connector is the same form factor as the stock Cluster and also has the pin numbers molded into the connector itself. Although it uses the same connector as the stock cluster, the Rally Gauge cluster has a different pin-out.

The following diagram illustrates the pin-out of the connector for a Rally Gauge cluster:

Gauges (Rally Cluster)

Pin #  Wire Color    Usage
1   BLUE/WHITE Stripe  Oil Pressure Gauge
2   GREEN    Water Temp Gauge
3   Light TAN    Fuel Gauge
4   GRAY     Illumination Lights
5   N/A
6   GRAY     Illumination Lights
7   Light BLUE    Left Turn Light
8   Dark TAN    Brake Light
9   Medium BLUE   Right Turn Light
10   PINK (2 wires)   GROUND (see note below: +12VDC)
11   WHITE    Volt Gauge
12   BLACK    Volt Gauge

The TEMP, OIL, and ALT gauges, as well as the BRAKE indicator in the Rally Cluster are used to notify the driver of a possible trouble condition under the hood of the car. The wires associated with these gauges and indicator on the Rally Cluster connector will get connected to wires located in either the “engine harness” or “forward lamp harness” under the hood of the car. These connections are made through two connectors on the firewall of the car.

Under the hood of a 1967 Firebird, on the firewall just below and to the right of the brake master cylinder, you will find two 10-pin connectors, with two wiring harnesses attached to them. When standing in front of the car facing the firewall, the connector on the left is the “Engine Harness” connector, and the connector on the right is the “forward Lamp Harness” connector. The following diagram shows the connector positions and wire colors associated with indicators on the stock cluster:

 +---+---+ +---+---+
 |      |  * | Dark TAN  |     |     |
 +---+---+ +---+---+
 |      |     | |      |     |
 +---+---+ +---+---+
Dark GREEN  |  *  |     | |      |     |
 +---+---+ +---+---+
 Dark BLUE |  *  |     | |      |  *  | BROWN 
 +---+---+ +---+---+
 |      |      |           BLACK |  *  |  *  | BLACK w WHITE Stripe
 +---+---+ +---+---+ 

The Dark TAN wire connects to a pressure sensitive switch on the brake master cylinder. This wire gets connected to the Dark TAN wire of the cluster connector and is used to turn on the BRAKE light if the line pressure in the master cylinder drops below a safe level, (indicating loss of fluid, internal seal failure, or open brake line.)

The Dark GREEN wire is connected to the coolant temperature sending unit located on the engine. This wire gets connected to one of the GREEN wire of the cluster connector and is used to send the voltage signal from the sending unit on the engine to the TEMP gauge on the Rally Cluster.

The Dark BLUE wire is connected to the oil pressure sending unit located on the engine. This wire gets connected to the “BLUE with WHITE stripe” wire on the cluster connector, and is used to send the voltage signal from the sending unit on the engine to the OIL gauge on the Rally Cluster.

The BLACK and “BLACK with WHITE Stripe” wires are used for the ALT gauge. These two wires are of a heavier gauge than most of the wires in the forward lamp harness because they have the potential to carry higher current levels than either the TEMP sending unit or OIL sending unit wires. The “BLACK with WHITE Stripe” wire is connected to a one end of a “fuse link” near the voltage regulator. The other end of that same “fuse link” is connected into the “power distribution splice” via an even heavier gauge red wire. The power distribution splice is a group of four very heavy gauge red wires, (contained within the forward lamp wire harness”), which are soldered together very near the voltage regulator. This splice distributes the output of the alternator to the horn relay, voltage regulator, charging junction block near the battery, AND one side of the ALT gauge on the Rally Cluster. A “fuse link” is a wire, which is designed to “open up” should too much current pass through it. (Consider it a fuse in the form of a wire, which is easily identified by rubber-like insulators at both ends.) The BLACK wire is connected to one end of a “fuse link” near the junction block by the battery. The other end of the same “fuse link” is connected to junction block itself via a heavy gauge red wire. The “BLACK with WHITE Stripe” wire of the forward lamp harness gets connected to the WHITE wire of the Rally Gauge cluster connector, (pin 11). The BLACK wire of the forward lamp harness gets connected to the BLACK wire of the Rally Gauge connector, (pin 12).

Steps to Convert from Stock Cluster to Rally Gauge Cluster

A first timer should expect the process take an entire weekend.

After studying the above diagram, you should have noticed that the Rally Gauge cluster has three additional wires that the stock cluster does not: 1) a BLACK wire, 2) a WHITE wire, and 3) a SECOND GRAY wire. You should also have noticed the BROWN (generator light) wire is missing. The Rally Gauge cluster does not use the BROWN wire.

Wire Harness Upgrade Options

You essentially have two options for converting your stock cluster to a Rally cluster car. Of course, both options start with obtaining a functioning Rally Gauge cluster, oil pressure sending unit, and coolant temperature sending unit. The two conversion options are differentiated by how you will “wire up” the new cluster.

Sending Unit GM p/n, Cost Classic Ind., Cost Niehoff n Borg Warner, Cost
Water Temp 12334869, $17.43 G1872, $17.68 DR134A, $5.33
Oil Pressure 14039612, $57.00 DR135T, $17.22

Option I – Replace wiring harnesses

For those with unlimited budgets, and a fear of messing with wiring harnesses, this is the way to go. Classic Industries and Year One both sell replacement wiring harnesses. You will need to replace both the “Front Lamp Harness” as well as the “Instrument Panel (Dashboard) Harness”. Be sure you order the version of these harness which specifically say “for cars with Rally Gauge cluster”. The forward lamp harness currently lists for $199.00, and the instrument panel harness lists for $399.00.

The appeal of this option is that no rewiring is necessary, just the times to remove your old harnesses and replace them with the new harnesses.

Option II – Modifying existing harnesses

For most of use, the cost of replacing the wiring harnesses in our cars is prohibitive. Here is a way to make do with your existing harnesses.

1 Copy Connector Wiring and Disconnect the Battery

The first step is to prepare for the “under the dash re-wiring” by printing off, or drawing out the cluster connector diagrams for both the standard cluster and Rally Gauge cluster. This will make re-pinning the cluster connector much easier. This is also a good time to remove the battery from the car!!!! This is also the time you will want to replace all the bulbs in the Rally cluster since they are easily accessible.

2 & 3 Remove the Original Cluster and Remove Connector Wires

Once the stock cluster has been removed, step three is to remove all the wires from the cluster connector itself. This is a simple process once you know the trick. At the end of each wire is a metal “pin” which is held into the plastic body of the connector by a “tab” on the pin. Using a very narrow flat-blade screwdriver, (I used an eyeglass-screw screwdriver), insert the blade of the screwdriver below each wire, (the screwdriver is in between the wire and the center of the connector), until it bottoms out on the front of the connector. You should now be able to gently remove the wire with its attached pin from the connector. Do this for all the wires in the connector. Once you have completed step three, and all the wires are free from the connector, you are ready to begin altering the instrument panel wiring harness.

4 Tape Off Unused GREEN Wire

Step four is to remove one of the two GREEN wires – the one which goes to the ignition switch. This wire was used to light the TEMP light when the key was in the “START position”, and is not needed. (I recommend you just clip this wire and tape off the ends – you may want to restore the car to its stock configuration some day.)

5 Splice Brown Wire onto GRAY Wire

Step five is removing the BROWN wire and using it to splice into the GRAY wire. If you study the Rally Gauge cluster connector pin-out, you will see that the Rally gauge needs two GRAY wires to supply voltage for the illumination lights. Since the BROWN wire is not needed, you can use it, and its connector pin to splice into the existing GRAY wire and supply the as the “second” GRAY wire. Make sure you leave yourself plenty of wire so clip the wire at least six inches down from the pin.

6 Reconnect Wires into Connector

Step six is to reinsert the wires you now have back into the connector, according to the Rally Gauge pin-out diagram. Remember, your BROWN wire is now one of the two GRAY wires. (It doesn’t matter which one.)

Wiring the Volt Gauge Circuit

By completing steps one through six, you now have successfully re-pinned your cluster connector to work with a Rally Gauge with the exception that the volt gauge will be inoperative if you stop at this point. To get the volt gauge operative, you will need to add two additional wires. Since the metal pins for the cluster connector are hard to come by, the following steps illustrate how to connect the volt gauge wire to the cluster, without going through the cluster connector. I recommend going to your local hardware store or home improvement store and picking up 20 feet of exterior grade, insulated, two conductor extension cord. This is the type of wire that is typically used in exterior grade extension cords. The covering is usually BLACK rubber and the conductors inside are BLACK and WHITE. Since this type of wire is designed to carry 120V, it is of sufficient gauge to handle the current flows of the Firebird’s voltage gauge. Another bonus of using this type of wire is that the covering is NOT likely to rub off and cause a short. (The stock voltage gauge wires are heavy duty as well). You will also need to pick up a package of “round eyelet” type wire ends. You will need three. (You will use two of these to attach the wires to the back of the gauge cluster, and to attach one of the wire to the power junction block near the battery.) Also pick up a package of rubber grommets that have the interior diameter to match the wire. You will want to use a grommet where the wire goes through the firewall. On you way home from the hardware store, stop by your favorite auto parts store and pick up a couple of “orange” fuse links as well. Fuse links are rated by their color, and that is why I specified “orange”.

7 Terminating Volt Meter Circuit Wires at the Cluster

Step seven is where you want to attach the round wire ends to the BLACK and WHITE wires at one end of the extension cord. I recommend removing three inches of the exterior insulation. You can either solder or crimp these connectors on to the wires. Now looking at the back of the cluster, you will see two screws where the flexible circuit board attaches to the voltage gauge. Attach the WHITE wire to the left screw and the BLACK wire to the right screw. (This is where the round wire ends come in handy since there is no way the wire can come off unless the nut falls off. This makes a good solid connection.

8 Preparing the Firewall for the Volt Gauge Wires

Step eight is to find a suitable place, and drill a hole through the firewall for your new “wire harness”. I recommend just above the fuse block. The size of the hole will be dictated by the “hole diameter” specification of the grommets you will use. Drill the hole, use a round file to smooth out the edges, and then install a grommet in the hole.

At this point, it is a good idea to reinstall the cluster in the dash. That way you will be able to see the best way to route the new wire from its permanent resting spot on the back of the cluster to the hole in the firewall.

9 Installing Volt Gauge Wires in Firewall

Step nine is to fish the wire through the opening in the firewall, and then up along the inside of the left front fender, preferably along side of the forward lamp harness. A trick here, (and no comments from the peanut gallery), is to use KY Jelly on the wire before fishing it through the grommet. Since the outer covering of the cord is rubberized, and the grommet is more than likely rubber also, the KY Jelly allows you to slip the wire through the grommet with easy, and since it is water soluble, it cleans right off with a damp rag. I just taped the cord to the existing forward lamp harness. Once you have the cord fished to the front of the fender, you will come out by the voltage regulator. Very carefully strip off the outer covering, exposing the BLACK and WHITE wires contained within. (You should have about ten feet of each hanging there.)

10 Terminating Volt Gauge Wire at Voltage Regulator

Step Ten is to connect the WHITE wire to the “power distribution splice” near the voltage regulator, via one of the two fusible links you bought. The “power distribution splice” is a group of three very heavy gauge red wires located in the forward lamp harness very near the voltage regulator, which are soldered together. You will have to open up the forward lamp harness to find it. I highly recommend you solder the fuse link to the WHITE wire and then solder it into the “power distribution splice” as well.

11 Routing Volt Gauge Wire to Battery Power Junction

Step Eleven is to take the BLACK wire and route it over to the power junction block by the battery tray. The best way to do this is to tape the wire into the forward lamp harness which runs along the top of the radiator support. The wire is held onto the radiator support via nylon clips which are taped into the wire harness. You can remove the harness from the radiator support by pinching the tabs of the clips with a pliers and push the tabs back through the hole. The clips will be reusable to reattach the harness to the radiator support.

12 Terminating Volt Gauge Wire at Battery Power Junction

Step twelve is to connect the BLACK wire to the power distribution block via the second orange fuse link you bought. Solder one end of the fuse link to the BLACK wire. Attach a round eyelet connector to the other end of the fuse link. Now attach the fuse link to the power junction block.

13 Reconnect Battery and Test

Step thirteen is to reinstall the battery, then test out the gauges.

A: I used the above procedure on doing the swap. It was very helpful and I recommend anyone doing this to follow it. I did notice a couple of errors:

1. The pink wire that plugs into plug location #10 on the rally cluster connector is +12VDC, not Ground as stated in the procedure. The cluster gets it ground through the shield of the speedo cable. I added a ground wire to the speedo cluster by terminating one side to a screw on the speedo housing, and the other side to metal location on the steering column.

2. The unused “Generator” lamp (Brown wire on stock cluster) does not need to be cut. As stated in the procedure, there is a second Grey (connects to plug location #6 on rally cluster) wire required for the rally cluster’s dash illumination, not supplied on the stock cluster wiring. The rally cluster’s circuit card has a built in jumper between plug location #4 and #6, so an extra wired connection is not needed. Just tape off the unused Brown Generator wire in case you return the cluster to stock later.

A: I would recommend buying a Lyle connector pin remover instead of using a screwdriver to remove the pins from the connector. You greatly reduce the risk of damaging the connector and the pins. It cost about $10.

I would also recommend not cutting off any unused connector pins. Just use heat shrink around the pin and tape the unused wire down to the harness.

A: 1968 ralley gauge pin location is: 8-illumination, 14-left signal, 15-right signal, 30-fuel sender, 31 -oil press, 33-brake warn. indicator, 35- water temp, 39-ign(batt), 105-ammeter(batt), 106 ammeter(gen) or alternator. tThese are the GM “circuit #s and are pretty much universal as far as the colors and the useage with corresponding #. I cant draw a diagram like above so here:

is pin 8 has a jumper that ties pin 1,3 – 30 is pin4- 35 is pin5 -31
is pin6-14 is pin 7-33 is pin8-15 is pin9-39 is pin 10-105 is pin 11-106
is pin 12.
And I will restate this again for everyone that all 3 wiring harnessses must be changed to make this conversion work. NO SHORTCUTS. You CANNOT just change pin location.

1968 Ralley gauge circuit board Diagram from the 1968 Diagnostics service manual

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