Reference Manual

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Chapter 6: Electrical/Interior: Rallye Pac Conversion

The standard Oldsmobile Cutlass instrument panel, with little more than a speedometer, fuel gauge and a collection of "idiot" lights leaves much to be desired for anyone with the least bit of interest in what is happening under the hood. Fortunately, Oldsmobile offered, as an option, an instrument panel that included a basic set of gauges and this instrument panel can be swapped into a G-body that was originally equipped with the standard instrument panel with some minor rework of the original wiring.

Parts required:

"Rallye Pac" Gauge Cluster Assembly

Water temp sender (single terminal)

GP Sorenson p/n tsu64

or

the equivalent

Oil sending unit for cluster with gauges

GM p/n 14036243

or

GP Sorenson p/n ops88

or

the equivalent

Brass extension for oil sender to clear the intake manifold and cruise control bracket.

GM p/n 401559

or

1/8" NPT brass 45° elbow and a 2" long 1/8" NPT brass nipple

or

the equivalent

18awg wire

Tools required:

• 5.5mm socket
• 7mm socket
• 1/4" socket

Time required:

While not difficult, a few things related to this swap may take some time to work out. Although it may take less time, plan on an afternoon to complete this conversion.

Overview:

The standard Oldsmobile Cutlass instrument panel is wired differently than the cluster with gauges. For this reason a swap from the standard cluster to a Rallye Pac cluster will require the rearrangment of the terminals in one of the cluster connectors.

From the above charts, the first thing you might notice is that all functions use the same color code for each function wire, for both clusters. Not quite so obvious at first glance, the standard cluster uses 2 each of the illumination and ground leads, whereas the gauges cluster uses only one of each.

This means that when doing this swap you'll have an extra ground and an extra illumination wire. Because for both clusters each connects to the same location in the wiring harness and all are of the same gauge, which of each you use for the swap is irrelevant and the extra of each wire will need to protected from shorting out and stuffed away behind the dash.

The Procedure:

• The first step is to remove the original cluster.
• With the original cluster removed, push the locking tabs on either side of connector 2 toward the center of the connector and push the connector in so that it passes through the instrument panel adaptor.
• Connector 2 can then be passed through the larger opening above it's installed location and pulled away from the i.p. adaptor so that you can gain access to the terminals.
• Each terminal is secured in the connector shell by a locking tang. To remove a terminal you must insert a small pick, awl, jewelers screwdriver or similar tool between the terminal and the connector shell to depress the tang, releasing the terminal. With the tang depressed, the terminal will pass through the shell by pulling on the wire. Do not use force! When the tang has been sufficiently depressed the terminal will pull out easily with little to no effort.

• While the terminals are removed, inspect each terminal closely for any corrosion or tarnish. If any corrosion or tarnishing is present, remove it using an eraser or a cloth soaked in rubbing alcohol. Do not use an abrasive, each terminal is steel with a thin copper coating, the use of an abrasive will degrade the copper coating allowing the steel terminal to corrode.
• Rearrange the terminals in Connector 2 by color code using the chart below:

• When reinserting the terminals into the connector shell, it is very important that the tang be bent away from the terminal so that it will be able to properly secure the terminal in the shell. If this is not done, or done improperly, it's likely that the terminal will slip out of position in the connector shell and make poor, or no, contact with the cluster. Resulting in inaccurate, or non-functional gauges or functions. An easy way to check each terminal is to push on them as if removing them from the housing, if the tang is holding the terminal in the housing, the terminal will only move a short distance in the connector housing.

• Looking at the chart above, you'll notice that the Standard Cluster uses 2 each of the Illumination and Ground wires, while a Gauges Cluster uses only one of each. The spare of each of these lead wires should be protected from shorts (such as with electrical tape) and securely fastened to the wiring harness behind the cluster to prevent future problems.
• This will leave 2 circuits that will require special attention:
  • The Tachometer
    • Method 1 (Recommended)
      • Install a wire, with terminal, in Connector 2, position 14 (White to match factory color, ideally)
      • Route this wire through the firewall to the distributer
      • Attach a 1/4" Quick Disconnect terminal to the wire and plug this QD terminal into the Distributer TACH terminal
    • Method 2 (The cleanest)
      Check your distributer, if there is already a white wire connected to the TACH terminal, you could use this method.
      • Install a wire, with terminal, in Connector 2, position 14 (White to match the factory color, ideally)
      • Remove the two screws from the opposite corners of the fuse block
      • Pry out the tabs at each corner to seperate the fuse block from the bulkhead connector.
      • From under the hood, loosen the 1/4" captive screw in the center of the bulkhead connector holding the two halves of the buckhead connector together.
      • Pull the bulkhead connector apart
      • Obtain a proper terminal for the bulkhead connector and attach it to the end of this wire
      • Insert the terminal into the bulkhead connector at position A7
      • Reassemble the bulkhead connector and the fuse block
  • The Coolant Temperature Sensor
    • Method 1 (Recommended)
      • Insert the existing Dk Green wire into Connector 2, position 7
      • Remove the original Coolant Temperature Sensor
      • Install the Sensor listed in the Parts list or it's equivalent
    • Method 2 (Harder)
      This method will alleviate the need to change the Coolant Sensor if your engine has a two terminal Coolant Sensor.
      • Remove the two screws from the opposite corners of the fuse block
      • Pry out the tabs at each corner to seperate the fuse block from the bulkhead connector.
      • From under the hood, loosen the 1/4" captive screw in the center of the bulkhead connector holding the two halves of the buckhead connector together.
      • Pull the bulkhead connector apart
      • Remove the terminal at D5 (Dk Green or Dk Green/Yellow)
      • Reinstall this terminal at location C6
      • Reassemble the bulkhead connector and the fuse block
    • Method 3 (The most difficult)
      Warning: This method will irrevocably alter your wiring harness. Because the wiring harness is no longer available new from GM, this method should only be used after very careful consideration, and is not recommended.
      This method will give you a functional coolant temp gauge and a functional coolant temperature indicator.
      • Extend the Dk Green wire at the Cluster Connector 2, position 11 of the standard cluster to reach Connector 1 and install in position 4 (this maintains the bulb test function of the coolant temp indicator).
      • Modify the Ignition input lead, Pink/Black, to also connect to Connector 1, position 5, and install.
      • Insert a new wire lead, with terminal, into Connector 2, position 7 (Dk Green/White to match the factory color, ideally).
      • Remove the two screws from the opposite corners of the fuse block
      • Pry out the tabs at each corner to seperate the fuse block from the bulkhead connector.
      • From under the hood, loosen the 1/4" captive screw in the center of the bulkhead connector holding the two halves of the buckhead connector together.
      • Pull the bulkhead connector apart
      • Obtain a proper terminal for the bulkhead connector and attach it to the end of this wire lead.
      • Insert this wire terminal into the bulkhead connector at position C6
      • Reassemble the bulkhead connector and the fuse block

Installing the Oil Pressure Sender

• Disconnect the lead wire from the Oil Pressure Switch.
• Remove the original Oil Pressure Switch.
• Install the brass extension.
• Install the Oil Pressure Sender.
• Connect the original lead wire to the Oil Pressure Sender.

Optional method to keep the Oil Pressure Switch and indicator functional:

• Disconnect the lead wire from the Oil Pressure Switch.
• Remove the original Oil Pressure Switch.
• Install a 1/8" brass hex nipple in the block.
• Attach a brass 45° elbow to the nipple.
• Attach a brass Tee to the elbow.
• Install the Oil Pressure Switch in the upper port of the Tee.
• Install the Oil Pressure Sender in the remaining port of the Tee.
• Connect the original lead wire to the Oil Pressure Sender.
• Connect a new lead wire to the Oil Pressure Switch and route the wire to cluster connecter 2 and install in position 8.

Setting the Tachometer:

The tachometer can be set to indicate RPM for a 6 or 8 cylinder engine by means of a jumper accessible from the rear of the gauge cluster housing.

1.   Instrument Cluster Assembly

2.   Shorting Adapter

 

Calibrate the tachometer by installing the shorting adaptor in the hole that matches the number of engine cylinders (6 or 8).

or

This would be a good time to consider replacing the jumper with a soldered connection to eliminate possible future problems.

Addressing the issue of the Odometer:

• The Legal Situation:
  
  When replacing a speedometer assembly, the law requires the odometer reading of the replacement unit to be set to register the same mileage as the prior odometer. If the same mileage cannot be set, the law requires that the replacement odometer be set to zero and a label be installed on the driver's door frame to show the previous odometer reading and the date of replacement.
• Now the good news. The odometer assembly used in a standard cluster is identical to that used in the gauges cluster.

Cleaning the gauge faces:

• Don't do it. The ink used to print the gauge face is water based. A liquid based cleaning fluid, or even water, will smear the printing or even completely remove the printing.