INSTRUCTIONS FOR INSTALLING GM 12-21 ADAPTER

Some people find it necessary to first remove the triangular support bracket (with the hole in it) that you see at the back of your radio opening in the dash. This is held to the console support by two metal rivets. Removal of this bracket is not always required for installation of the new radio, so don't remove it if you don't have to. If you choose to leave it, please make sure that the harness and antenna adapters are not sandwiched between it and the back of the radio. This could cause problems down the road. To remove the bracket, you will need to insert a large flat blade screwdriver or small pry bar between the bracket and the console support and twist. The bracket should 'pop' out. If you want to put the bracket back in, you will need to space it out about 3/16ths of an inch before you re-attach it.

On some Fieros (especially 88 models), you may find that a wiring harness plug from the AC is keeping your radio from sliding all the way to the back of the opening. To remedy this, simply remove the 7mm sheet metal screw that is securing the plug and push the plug up out of the way. After you slide the radio in, the plug will settle back down and rest on the top of the radio, but this shouldn't hurt anything.

When you go to install the adapter harness, you will find that there is one plug on each side of the adapter that is not used in most applications. This is illustrated in the top picture from above. This adapter will actually work for many GM vehicles from the 80's. Some of those vehicles have slightly different plug configurations.

On the CAR SIDE of the adapter, you will most likely NOT use the small black plug with one gray wire and two orange ones. You will also have to remove the black cap that is on the white plug. The white plug will then snap into the female plug (with orange and brown wires) that you removed from the back of the radio. Placement of the large black plug should be obvious.

For Pontiac radios, on the RADIO SIDE of the adapter, you will most likely NOT use the black and red plug with the orange, gray, black and tan wires. (It is supposed to be for steering wheel controls.) The long, skinny black plug goes on the bottom of the radio plug receptacle**, with the prongs facing down. The blue plug goes on the top left side** (when looking at the radio from the back), with the prong facing up. You will probably find that you need to trim some of the material off the triangular prong on the blue plug so that it will fit into the prong opening on the radio. If you trim too much and the plug doesn't seem to stay in place, simply wrap black electrical tape around it and the black plug to secure them to each other after you've installed both of them. Then the blue plug won't go anywhere.

** The plug is flipped upside down for most other GM radios, so the long black plug would go on the top and the small blue one would go on the bottom right.**

To install this package in a Fiero with the Performance Sound System, you must perform a wiring modification. You have 2 options:

1) Cut the two pink wires that lead from the amplifier (under the carpet on the right side of the car next to the console support in the passenger footwell), strip approximately 1/2" to expose the wire and twist them together. Then locate a yellow wire from the car harness (not from the radio harness) and splice the pink wires to the yellow wire. You can do this by scraping off a section of the covering of the yellow wire without having to cut that one).

OR

2) Cut the white wire (terminal E) in the middle of the adapter harness. Wrap tape around the end that goes to the radio side of the adapter. (This will no longer be used.) Bare a small section at the end of the other half of the white wire. Then bare (do not cut) a small section of the red wire (terminal F) and splice the bared end of the white wire into the red one. Wrap with electrical tape. (Alternately, you could use a wire tap to avoid stripping the red wire, but the results aren't always as good.)

Lastly, when you install the new radio, you will probably need to put spacers behind the radio brackets before you fasten them to the console support (with the 7mm screws.) Small washers work fine for this. You will need either one or two small washers per hole. If you don't put spacers behind the brackets, there will be a 1/8" gap between the trim plate and the face of the radio.

Please let me know if you have any other questions. My email address is radios@replacementradios.com