Gauge Modification

Upgrading Stock Gauges

The following "Ho To" will show how I replaced my stock gauges with aftermarket units while still maintaining the stock gauge array. The modification is pretty simple but take patience and time.

Tools needed:

Wire cutters
Philips and Flat Headed Screwdrivers (assorted sizes)
Shrink Tubing & Soldering Iron or Wire connectors (This depends on how you wish to connect any cut wires) Preferred method is soldering!
Electrical Tape
The Cars Electrical Schematics
12v indicator lights. These can be purchased at any auto store. I found the following indicator light at Trac Auto for $3 a piece. These are a perfect fit into the existing gauge plate without modifications.

Gauges:

Any gauges this size will work. You can substitute mechanical gauges for the electric ones to eliminate cutting the stock Oil and Temp wires off the stock gauge cluster plug. I used all Autometer Ultra Lite electrical gauges on my car.

3 3/4" Speedo
3 3/4" Tachometer
2 1/16" Oil Gauge (Electric or Mechanical)
2 1/16" Temp Gauge (Electric or Mechanical)
2 1/16" Volt Gauge (Electric)
2 1/16" Fuel Gauge (Electric)

Getting Started:

Remove negative battery cable.

Remove dash face plate by removing the upper 5 screws. Pull the top out towards you and lift up to release the bottom locking tabs.

Next remove the gauge cluster by removing the 4 outer screws. While removing the gauge cluster unhook the two electrical plugs from the back of the gauge cluster by squeezing the release clips located on each plug. Also remove the Speedo cable by pressing the release clip inward towards the back of the gauge cluster and finish removing the gauge cluster.

Remove the plastic circuit board from the rear of the gauge cluster. You will need to remove all the dash lights as well from the gauge cluster.

Remove the clear plastic face from the gauge cluster. You will want to use a sharp knife or chisel to remove the clear plastic lens. Be very careful not to crack the clear lens.

Next remove the 4 outer screws to release the cluster face plate from the gauge cluster mounting panel. Save this plate and panel!

The gauges themselves will now be visible. Remove all the gauges from the gauge panel.

Remove the 4 small gauge inner rings from the gauge cluster face plate as illustrated in the following picture. Look close at the bottom right corner you will see that the inner non round ring of the smaller gauge holes has been cut out to 2 1/16".

Install the gauges according to the manufacturers directions. The gauges (if the correct size as stated above) will now bolt to the modified gauge cluster face plate.

You will now need to hack up the original gauge cluster backing plate. You will want to save the turn signal portion and each end piece as illustrated in the picture below. Bolt the modified pieces to the gauge face plate as illustrated below. Note that the end pieces on this gauge cluster have been cut off the original piece. This allows you to mount the gauges with the factory bolts and bolt locations.

The following list of wires are specific to the 85 Mustang GT. Refer to your electrical schematics for your year car.

Oil Sender Wire = White w/Red stripe.

Temp Sender Wire = Red w/White stripe.

Tachometer = Dark Green w/Yellow stripe.

Dash Illumination Wire = Light Blue with a Red stripe.

Left Turn Signal Wire = Light Green w/White stripe.

Right Turn Signal Wire = White w/Light Blue stripe.

High Beam Indicator Wire = Light Green w/Black stripe.

Safety Belt Light = Dark Green w/Light Green stripe.

Low Oil Light = Red w/Yellow Hash + Black w/Light Blue stripe. Red is hot, black is trigger from relay.

Brake Light = Red w/Yellow Hash + Pink w/White stripe. Red is hot, Pink is trigger from relay.

Upshift Light (5speed) = Black w/Yellow stripe + Gray w/Black stripe. Black is hot, Gray is trigger from relay.

Power From Switch = Red w/Yellow Hash Line There are two of these wires feeding the gauge cluster. Split the load on each lead between all the components you will be connecting to them. This will ensure you don't over load the stock wires.

Ground = Black wire. Don't ground the gauges to this wire. Ground the gauges to the the dash frame near the brake assembly.

Either cut the wires listed above or use "Wire piggy backers" to hook into the wire so you do not cut the existing wires.

Follow the directions provided by your gauge manufacture for proper wire connection.

Once you have the gauges mounted it should look something similar to the following picture. The larger gauges will fit right into the existing holes without modification. What cool about this size gauge is that when mounted in this cluster the Speedo and Tachometer angle up towards the drivers view. All the other gauges point straight out.

Once the gauges are in place we must address the turn signal issue. Some state laws require you to have working indicators for you turn signals and high beams. To solve this issue since we have removed the factory plastic circuit board that used to power the indicators I ran down to my local Trac Auto and picked up some generic indicator lights. These fit perfectly into the modified gauge plate.

Here's a picture of the indicator lights I used.

Here are pictures of the indicator lights in the modified gauge plate. They slide right in. Once the face plate is put on all you will see is the stock indicator arrows. Sweet!

This is a picture of the rear of the face plate where the indicator bulbs go. These indicator lights I purchased also fit into the side lights on the dash panel. You know the ones that say Fasten Safety Belts, Brakes and Shift. I found these lights in several colors including green, blue, orange, red and yellow.

Here are more shots of the turn signal indicators mounted in the gauge panel.

Since I rewired my entire car I scrapped the stock plugs and picked up a couple of 6 wire trailer plugs. These worked great the picture on the left is the dash plugs the plugs on the right are the gauge plugs. I can easily remove the gauges at any time.

Once the modified gauge plate is completed you will need to modify a small portion of the dash to allow the gauge cluster to fit into the stock location. The modified portion is illustrated below.

Once the portions above have been removed insert the gauge cluster and ensure proper fitment.

Once you have verified the proper fitment connect all the wires and Speedo cable to there corresponding points and bolt the gauge cluster and face plate back into the stock dash panel. Note that the stock Speedo cable will not screw on to the new Speedo gauge it will merle slip over the gauge Speedo connection. Once everything is in place you should not have any problems with it coming loose.

This is what the final product looks like. Without a doubt this looks far better than the over popular white face gauges overlays. The gauge accuracy is probably tens times better.