89 mustang - factory amp?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=45391
Printed Date: April 23, 2024 at 11:00 AM
Topic: 89 mustang - factory amp?
Posted By: Hoss10
Subject: 89 mustang - factory amp?
Date Posted: December 16, 2004 at 11:09 PM
Hi everyone, this is my first post here. I'm installing a Sony receiver in an 89 Mustang with 6-speaker option, and keeping the stock speakers for now. What I'm wondering is if anyone is familiar with the particular setup in these cars, how the factory amp works, and how the stock 4 speakers on the front channel are hooked together. I'm assuming from past experience that I'm going to have to bypass the factory amp, and that leaves me with the question of how do I attach all 4 front speakers without overloading the receiver. Also, is there a factory amp bypass harness available that fits these cars like the JBL bypass setup works in the newer ones. Is it possible that the front door and dash speakers are setup with a crossover, and would bypassing the amp disable the crossover? Should I just go ahead and connect the Sony to the plugs that I disconnected from the back of the stock head unit with my Metra two-plug Ford kit, and just run it through all the factory amps and wiring and stuff, and would this hurt the receiver? I've done many installs before and this car is boggling my mind. If anyone is familiar with the setup in these cars and can offer some assistance I would be greatly appreciative.
Replies:
Posted By: sinister audio
Date Posted: December 16, 2004 at 11:53 PM
just connect it to your metra kit you should be alright. you could also take a multimeter to the factory harness and check your ohms but im sure it will be about 4ohms for each spot if its a little less it shouldnt hurt your deck but if its like 1 ohm then it will but im sure itll be between 4-8ohm
Posted By: tech460
Date Posted: December 17, 2004 at 10:32 AM
I am familiar with this car and I can answer most any question you have. As far as the harness you have you will not be able to use it unless you bypass the amp and I would have to explain to you how to do that. It is a 70-1770 I presume? Now as far as keeping the amp, Metra makes a harness for this vehicle to keep the amp if you so desire but I would'nt keep it. That part is 70-1768. Now as far as the speaker impedance go's, don't worry about it, it will fine powered by the Sony deck. Let me know what you want to do.
Posted By: Javelin3o4
Date Posted: December 17, 2004 at 12:45 PM
I cant remember for sure, but on some mustangs is if you look behind the radio or behind the glove box toward the radio there is a second harness that goes from the harness from the deck & factory amp to a plug that goes out to the speakers, which uses the standard Ford harness, if this is the car that uses that, all you would have to do is unplugg where the radio/amp harness meet the speaker out put and plug the harness you wired to your new deck into that. Ive done a mustang like that before, took a while to find the harness hidden behind the dash but afterwards it was just like doing a basic deck
Posted By: tech460
Date Posted: December 17, 2004 at 12:58 PM
Yes you are right. One harness is behind the radio on the right and one is on the left on top of the brace that runs left to right. Also keep in mind that when you bypass the amp this way you have to reverse the front speaker negatives as they are backwards from an aftermarket standpoint.
Posted By: Split
Date Posted: December 17, 2004 at 7:41 PM
I recently installed a Pioneer HU on my 93 GT,the dash speakers can be wired to the front doors speakers without any problem.The factory dash speakers has a filter to cut low frequencies.
Posted By: Hoss10
Date Posted: December 17, 2004 at 8:13 PM
Yes, the plug kit I bought is the 70-1770. I pulled the stereo out last night and tried tracing some of the wiring down, I'll have to look again to find the second harness. The only ones I saw were on top of the amp and were what looked like 4-wire, in a square pattern as opposed to the single-layer flat connector like what goes into the back of the radio. My personal preference I would like to bypass the amp if at all possible, I used to have a 93 Ranger that had the JBL premium sound and I ran into this problem with it. The factory amp exaggerated the volume so much that whenever I would unhook the battery my radio would return the volume to somewhere around 10, which eventually blew my door speakers. I bypassed the factory amp on it and it solved everything. From what it looks like the 70-1770 will snap right up to the connections that I unplugged from the back of the radio, so what I'm gathering is there's another plug somewhere back in the dash that is similar to those that I want to connect my Metra kit to? Also, I'm trying to figure what you mean when you mentioned the front speakers negatives are reversed. I'm assuming you mean reversed between the left and right channel, or do you mean polarity? Just out of curiosity, does anyone know if the front channels on this car are set up like component speakers with a crossover or are they just wired together? Just curious as this seems like such a mystery to me, plus I noticed that absolutely no bass comes out of the dash speakers, it sounds like there's some type of crossover or filter on them. Thanks for all the info, my goal at this point is to have it installed next week pending whenever my new Pioneer for my S-10 comes in. The Sony that I have in it now is going into the Mustang once it shows up, but I started pulling it apart last night after reading through this so that I can plan out how to do it. I'm sure I'll be on here throughout the week at least to update my progress on it, but probably with more questions.
Posted By: Hoss10
Date Posted: December 30, 2004 at 7:00 PM
All Done! Got it all hooked up and it sounds pretty good, couldn't have done it without this site! I found the plugs that were mentioned back behind the glovebox so I unplugged them and then took the factory amp and the amp harness out, what a ton of wiring for a stock radio! The kit that I got for it turned out OK even though I had to cross a couple wires to compensate for Ford's reversed front speaker negatives. It fit the plugs that I found behind the glovebox (which looked the same as the plugs going into the back of the stock radio), so I plugged my Metra kit into those plugs. I got all six speakers working just like it did before and it actually doesn't sound bad at all for stock speakers. Tech460 I figured out what you meant by the reversed speaker negatives when I took my diagram I printed off of this site and traced each wire down, bigtime thanks for the heads up, saved me a lot of trouble and frustration as I wouldn't have even though to check that. I just can't figure why Ford would use those plugs and reverse two wires in it, seems kinda goofy and real easy to screw up when going aftermarket. Install looks real clean too. Thanks everyone again for all the help.
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