Is a '93 Explorer cd head unit compatible w/'91 JBL harness?

[Thallarsen]

I'm trying to replace my '91 factory am/fm cassette head unit (JBL sound) with a '93 factory cd head unit. I have an Alpine RF 6 disc changer that works well with the factory system, but I want to improve my cd sound.
The cd head unit fits perfectly in my '91, and the two factory plugins (& antenna)fit in the back of the cd unit effortlessy. However, the cd unit has a double "spade" plugin adapter in the square 4-pin plug outlet - upper right corner. The '91 harness doesn't have a plugin that fits this.
The unit powers up, but I get no sound whatsoever.
Are these units compatible? If so, Is there a small modification that can be done? Are there more than two plugins for the '93?
Any suggestions would be greatly appreciated.

J.P.

 

[cobrajeff]

The factory DIN-size CD Radio from 1993 is a plug-in replacement for your '91 Premium Cassette w/JBL.

The square blade 4-pin adapter is a "shorting plug" that was needed with some models of the radios. Some models have the pins shorted together internally, some need the plug.

I think your problem is a difference in the voltage supplied to the amp "turn-on" line. I think your amp is looking for a 12V signal, while your later radio is sending a 5V turn-on signal. I have gotten around this before by jumpering the 12V signal for the power antenna lead to the amp turn-on circuit (a jumper on the harness side of the radio power connector will do it).

Regards,

Jeff