Making a Wiring Harness to use a Newer Delco Radio in your Fiero

There are a number of reasons you may want to install a newer Delco radio in your Fiero. A newer radio may be in better condition than your stock radio. Newer Pontiac radios can retain a stock appearance while adding additional features--more presets, a graphic equalizer, or even an in-dash CD player. Many also have a nine-pin connector on the back for the addition of a factory 6 or 12 disc CD changer. Newer radios and CD changers can both be purchased from a number of online sources (see links to a couple at the end.) I bought mine off ebay.

My Fiero cassette player had been a little noisy since I bought the car, and the auto reverse was starting to get a little flaky. After reading the history of Skitime's car on Pennock's Fiero Forum, I decided I liked his addition of a factory CD changer, so I began shopping for a newer radio to accommodate a factory CD changer. I found a unit for the right price on ebay. It's from a Chevrolet, I believe, so the illumination doesn't match the dash lighting and it doesn't look exactly stock, but I like the layout and features. Pontiac radios have amber illumination that will match your existing dash lighting.

Newer radios will require a wiring harness and antenna adapter to work in your Fiero. These can be purchased through a number of online sources. However, if you have more time than money, you can make a wiring harness adapter yourself.

The wiring harness that attaches to the back of a newer radio consists of four plugs: two four-pin plugs and two six-pin plugs. (See photo.) Only three of the plugs are necessary for basic operation. The four-pin plugs (white and blue) contain the speaker wiring while the black six-pin plug houses the power and control wires. The second six-pin plug may be present only in Pontiac vehicles, and isn't necessary for basic operation. The antenna plug is smaller on newer radios, so you'll need an antenna adapter as well.

Cut the wiring harness out of a junkyard car. Also cut the last 6-8 inches (the radio end) off the antenna lead. I found the wiring I needed in an early '90s Lumina. I think I paid $5 for the wiring and antenna lead along with several other small items I had pulled. If you want, you can simply splice the new wiring harness into the existing wiring, but I made an intermediate wiring harness that would plug directly into both the new radio and the existing Fiero wiring. This allowed me to do the work in my living room while relaxing in front of the TV, and simply plug it into the existing wiring. Additionally, should I ever decide to return to a stock radio, if I sell the car, for instance, I can simply plug the radio back in, and keep my wiring harness for my next Fiero.

In making my adapter, pictured at left, the biggest difficulty I encountered was finding accurate and complete information on the wiring. I used a Scosche wiring harness (part # GM01) that I purchased at Wal-Mart to mate with the existing Fiero wiring. This part is the left part of the harness. I simply crimped the appropriate wires from each harness together. For the antenna adapter, I bought a Motorola jack (that's what the antenna connectors are called) from Radio Shack.

The wiring (and plug) colors following match both the existing Fiero wiring and the new wiring harness I retrieved from the Lumina. The pin numbers refer to the 20-pin wiring harness on newer model (1989+) Delco radios. From information I was able to find online, this chart appears to be fairly standard for many GM vehicles, and therefore may apply to any number of models. On the newer GM radios, the four plugs noted above are arranged in two rows of 10 pins, pictured here. Pins 1, 10, 11 and 20 are labeled on the radio for reference. In the photo, you can see the "20" in the lower right corner of the harness, and the reference for pin 11 is barely visible near the lower left pin. On various radios, the connector may be oriented right side up or upside down. Regardless of the orientation of the connector, the pin numbers are consistent.

The connector looks the same either way, and the speaker connectors will fit in either slot with the correct number of pins, so it is important to note the pin numbers. Additionally, pin reference numbers are imprinted on the wiring harness plugs.

White Connector
(Front Speakers)
PinWire Color & Function
1Left Front -
2Left Front +
3Right Front -
4Right Front +

Black Connector
(Power Connectors)
PinWire Color & Function
6Dim Signal 1
7Panel Illumination (dimmed) 2
8Power Antenna 3
9Ignition Input 12V (Switched with ignition)
10Battery 12V (Constant Power)

Six-Pin Connector
(Pins 11-17)

This connector is not present in my harness.
PinWire Color & Function
14Steering Wheel Controls (Pontiac Only)

Blue Connector
(Rear Speakers)
PinWire Color & Function
17Right Rear -
18Right Rear +
19Left Rear -
20Left Rear +

1 The dim wire is the second wire in the separate two-wire harness, along with the orange constant power wire. It may or may not be supplied with an aftermarket wiring harness. In order to ensure this function on your new radio, you may need to bypass the wiring harness and splice it directly to the new harness.

2 In the documentation I found online, the panel illumination wire was labeled gray. The illumination wire was gray in my Fiero wiring, but brown with a white stripe in the wiring harness from the Lumina.

3 Pin 8 is open in my wiring harness. My information indicates that this wire should be pink or yellow in cars equipped with a power antenna. Pin 8 is hot (12V applied) when the radio is tunred on, and can be used to switch amps or other accessories. If the wire is present but not used, it should be capped to avoid accidentally shorting it to ground.

Here is a visual diagram of the three plugs used for basic radio operation. This duplicates the information found in the table, but is laid out more like a schematic, and lists the color names.

GM/Delco Radio Wiring Links

Replacement Radios sells newer (1989+) radios with cassette & CD that can be adapted to work in your Fiero. They also sell the wiring harness described here. The guy that runs this site is a member of Pennock's (Kru) and sells in The Mall there as well.

Corvette Radios has lots of good information on audio "industry standard" wiring colors, with corresponding GM colors. They also have diagrams of GM wiring harnesses and pin assignments. Corvette Radios also repairs & sells and repairs Delco radios.

M & R Electronics sells & repairs Delco radios. They also sell the ready made wiring harness adapter detailed above.

AA Technologies also sells factory audio equipment--radios and CD changers.

DISCLAIMER: The information contained on this page is believed to be accurate, but the author makes no guarantee of any kind. This information should be used at your own risk.

My Fiero information is based on the wiring present in my 1984 model. Due to the similarities noted above throughout GM's product lines, I believe 1985-1988 models to be the same, but I do not have a later model at my disposal. The pinouts are the same for all 1984-1988 Fieros (along with a host of 1978-1991 GM vehicles,) so it is assumed that the wire colors are as well.

Copyright 2003-2004 Andy Larsen
Updated 4/23/04