1989 Thunderbird Premium Sound problems

I have a 1989 T-Bird with premium sound. I got the car with no head unit and when I put a premium sound unit in I have no sound at the speakers. I checked everything, (Including the new head unit. I checked that by swapping two other ones that I know work.) On checking I find out that I have no rear speakers, and the amp was by-passed. I installed new Premium sound speakers, (working ones) and hooked the amp up correctly, (removed the by-pass harness). Still no sound. I can hear the speakers "pop" slightly when I turn it on or off, but no "tunes". I also checked the amp with one that I know works. (I have an extra T-Bird, or two laying around.) I have seen on e-bay a unit that they advertized as a factory "pre-amp" that is supposed to be located in front behind the head unit. I looked and I have this part in all the "Premium Sound cars, but I have found no info as to a "pre-amp" anywhere else but e-bay. (I don't always trust what people on e-bay say as to what a part is for, or fits). This "pre-amp" would be very hard to get at, so if it is not likely the problem I would rather not mess with it. Also, the square plug to the head unit looks to be a little bit mangled. (Slightly, it LOOKS like it should work, but...). Is there a way to check if speaker power is getting to the amp in the rear? ANY other ideas? I don't want to swap the whole system since it has a slave CD, plus I have several extra parts for this set-up, and it's just a daily-driver anyway.

Did you check to see if the amp turn on wire is receving power from the head unit ?

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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA

The amp clicks when the radio is turned on, so it must be getting power. (Both amps I tried click). Also, the speakers "pop" slightly when turned on or off. This didn't happen before I removed the amp by-pass harness and hooked it up right. An interesting point though is that before I removed the amp by-pass I did get a little static at the speakers, (VERY little, you had to be right on top of them to hear it at all, and if there was ANY other noise you wouldn't hear it. No "tunes" though.) Shouldn't there be some way of testing at the amp to see if speaker input is coming through? I'm thinking that if I take the input plug and test there I should get a reading, I just don't know how to check it, or what kind of reading there should be. (I think that since the plug is messed up a little at the head unit maybe speaker power isn't getting to the amp). Also, how hard is it to remove the cable that goes from the head unit to the amp? Is it one cable all the way back, or is there a connector somewhere? I could just pull it from one of the other cars and see if that's the problem. (I don't really want to do anything too extensive though since the car I would be taking it from would probably be considered a "nice" car. But if it can be removed by pulling the seats and lifting the carpet I'll do it. Anyone know just where that cable runs?)

Does anybody have any of this info, or a way that I can try to see if I'm getting speaker power to the amp?

just curious... when you hooked this up did you connect the HU connector high level or low level?

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Kevin Gerry
Certified Electronics Technician
MECP First Class Installer

Owner/Installer
Classic Car Audio
since 1979

Ok, Now maybe we're onto something. HU connector??? What does it look like, where is it located, and what is the difference in the connection? All I did was try a couple of different head units, and amps, (that I know work), and put in some working (factory) speakers. I connected everything the way it would seem to connect. (Of course you can't really hook it up wrong since the plugs only connect to the matching ones). EVERYTHING is bone stock equipment, so it should work, but it doesn't. Please explain the HU connector. Also, since the previous owner had the amp by-passed (for a non-factory head unit obviously) could there be something more that needs to be done to put it back stock? All I did was remove the by-pass harness and hook up the amp. The way I see it is if the head unit powers up, the amp clicks when powered up, and I know all the hardware is good, then it almost HAS to be a problem in the speaker wiring to the amp, or from the amp to the speakers. Checking at the speakers is easy, but since NONE of them make sound then wouldn't it be more likely to be the wiring to the amp? That's why I need to know how to check at the amp, or how to remove the cable going from the head unit to the amp and replace it. (Or just hook up a different one and see if it works). I'm about to pull everything and put it in another car to see for sure. That way if it works it has to be the wiring.

Ok, I get it, duh, HU=HEAD UNIT. I'm not an audio buff (otherwise I probably wouldn't be bothering with the stock "Premium Sound" system anyway. As far as I know there is only one way to hook up the connector to the head unit. There are 4 possible plug ins, a long one for the power in to the HU, a small square one for the power antenna (I think), and 2 square ones for the slave CD, and the speaker output to the amp. (That is the one that is a bit mangled). I never tried to hook up the speaker one to the CD hole, it looks about the same size but I don't know if it would fit. I might take a quick look today just to see. Other than that what is the difference between hooking it up "high level" or "low level" (other than the difference in output power. What I mean is how can it be plugged in two different ways?) Someone out there must have either installed, or removed, a "Premium Sound" system from a T-Bird at some time.