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| GM cd radio question - 87 gt (Page 1/2) |
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domer94
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AUG 15, 12:25 PM
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i recently installed the GM cd radio in place of the aftermarket that was there using the provided adapter kit. my car has the subwoofer control in the overhead. i couldnt notice any action from the sub. was it designed only to work with the original cassete head unit? or should any other HU provide the output for it.
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hyperv6
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AUG 15, 03:24 PM
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I don’t have the diagram. But from memory you need to tap power into the GM plug. The amp was Fiero only and it needs spliced in.
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82-T/A [At Work]
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AUG 15, 03:26 PM
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No, it should work. The original subwoofer is meant to go inline of the factory radio... between the factory wiring harness for the speakers, and the radio itself. This is the subwoofer wiring...
The adaptor screws into the middle post behind the dash.
There could be a couple of things...
1 - Check to make sure Performance Sound (boost slider) is turned all the way up.
2 - Confirm that the speaker wire coming from the subwoofer is actually connected.
3 - Confirm that the amplifier for the subwoofer is present (it's located in the passenger side inner foot well, attached to the inside of the plastic piece).
This is everything included in the subwoofer system...
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82-T/A [At Work]
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AUG 15, 03:28 PM
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Just to add to what I said... the Fiero subwoofer will basically work with ANY radio at all... so long as you can get the output of your stereo into the same plug style as the factory harness.
Sometimes, when the factory subwoofer would fail, it would make a rattly sound as the cone failed, so people often disconnected it entirely. I say that from having seen multiple kits in the junkyard, and they're often disconnected on the wire that goes to the sub box.
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domer94
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AUG 15, 03:43 PM
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thanks, will check on all that stuff
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Vintage-Nut
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AUG 15, 03:45 PM
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You have the factory subwoofer amp, right?
The bottom line - the factory subwoofer amp has eight inputs that are designed to connect directly to the HIGH-LEVEL speaker outputs of a head unit.
If you have the factory service manual, the radio wiring and subwoofer is on page 8A-150-0
If you're having problem with the factory subwoofer system...
The Fiero Subwoofer System by Oliver Scholz
http://www.fieros.de/en/articles/sub.html
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Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles[This message has been edited by Vintage-Nut (edited 08-15-2025).]
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hyperv6
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AUG 15, 05:06 PM
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It may be due to mine being an 85. They never had a sub. I had to slice it to power.
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cam-a-lot
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AUG 16, 10:43 AM
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Great info guys Very helpful
I have a monsoon head unit and factory sub enclosure that I will be trying to connect. Factory amp is missing. Trying to find something compatible to drive it...
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Vintage-Nut
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AUG 16, 04:18 PM
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| quote | I have a monsoon head unit and factory sub enclosure that I will be trying to connect. Factory amp is missing. Trying to find something compatible to drive it...
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Car Mini-Monoblock Amps are uncommon these days; check motorcycle mono amplifiers like Kenwood KAC-M3001 {dimensions: 6-7/8"W x 1-13/16"H x 3-7/8"D} but it doesn't have a remote gain control ...
Look for physical size, high-level inputs, variable low-pass filter AND remote gain control as the “Performance Sound" gain slider assembly on the overhead console won't work with the 'new' amp without modifying it....
The 'smallest' mono-amps are around 100-watts / 150-watts @ 4 ohm {you really only need 20-watts} 
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Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles[This message has been edited by Vintage-Nut (edited 08-16-2025).]
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cam-a-lot
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AUG 17, 07:09 AM
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Thank you. Trying to find a compatible amp now.. not having much luck- but I don't really know what I am doing. Agreed, to drive that one sub, 40W should be plenty
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