Replace radio (head) in 1991 Celica GTS - Toyota Nation Forum : Toyota Car and Truck Forums

jiml8 · 02-02-2009, 09:35 PM

Hi, all. My first post here; I'm looking for some info.

I have a 1991 Celica GTS (which I purchased new in 1991) and I want to replace the radio. Basically, the CD player has not worked in years, and now the display light has blown so I can't see mode or what station it is on, or anything else.

This car has the high-end stereo. I don't recall who made it, but it has 10 speakers. I do have the Toyota shop manuals for the car, and the head shows up as a 4-channel head that feeds the power amplifier under the driver's seat.

Now, I have been shopping for a new double-din head and have looked at some nice Pioneers that would look really sharp in my dash, but the stores are telling me that I cannot plug one of these new heads into my existing amplifier. The problem, evidently, comes down to the output power of the new head. Apparently all the new ones will drive 50 Watts/channel.

Well, that leaves me with three questions, which I have not been able to answer so far. First, what is the output power of the stock head? Second, what is the maximum allowed input power of the power amplifier? Third, what is the output impedance of the head, and the input impedance of the amp?

If the amp has a high impedance input, then I can just connect a new head to it and the head's output power capability won't matter though I might have a bit more distortion at high volume (though I don't play it that loud). If the stock head and the amp are impedance matched, then I can't do this.

My existing head has a security system on it and to put it bluntly I don't recall whether I ever set that system up or not. If I did, it was a loooong time ago and I don't recall. Since the display on the head is dead, I can't even query the system to find out if the security system is enabled. Hence, I can't remove the radio to run diagnostic tests (such as measuring the power from the head, or drive the power amplifier to see how much power it can handle) because if the security system is set, this will leave me without a radio in the car until I get everything sorted out.

So, does anyone here know the answers?

concealer404 · 02-03-2009, 09:37 AM

Quote:

Originally Posted by jiml8

Hi, all. My first post here; I'm looking for some info.

I have a 1991 Celica GTS (which I purchased new in 1991) and I want to replace the radio. Basically, the CD player has not worked in years, and now the display light has blown so I can't see mode or what station it is on, or anything else.

This car has the high-end stereo. I don't recall who made it, but it has 10 speakers. I do have the Toyota shop manuals for the car, and the head shows up as a 4-channel head that feeds the power amplifier under the driver's seat.

Yep, System 10. 8"s in the doors, 6.5"s in the rear, 4"s in dash, and 4 tweets.

Quote:

Now, I have been shopping for a new double-din head and have looked at some nice Pioneers that would look really sharp in my dash, but the stores are telling me that I cannot plug one of these new heads into my existing amplifier. The problem, evidently, comes down to the output power of the new head. Apparently all the new ones will drive 50 Watts/channel.

Sure you can. You just need a Metra harness that will work as an adapter. The amplifier has nothing to do with the power of the headunit, and really nothing at all.

Quote:

Well, that leaves me with three questions, which I have not been able to answer so far. First, what is the output power of the stock head? Second, what is the maximum allowed input power of the power amplifier? Third, what is the output impedance of the head, and the input impedance of the amp?

1) Zero. The stock head has no output power. It's for signal processing only.
2) You don't power an amplifier beyond giving it a power source to draw on. (battery)
3) Doesn't matter.

Quote:

If the amp has a high impedance input, then I can just connect a new head to it and the head's output power capability won't matter though I might have a bit more distortion at high volume (though I don't play it that loud). If the stock head and the amp are impedance matched, then I can't do this.

You won't be using the headunit to power your speakers. You'll be using the amp. An aftermarket headunit will only be 4-channel, if you bypass the stock amplifier (under passenger seat) then you'll be losing use of some speakers. (Probably the 8s, and you don't want that)

Quote:

My existing head has a security system on it and to put it bluntly I don't recall whether I ever set that system up or not. If I did, it was a loooong time ago and I don't recall. Since the display on the head is dead, I can't even query the system to find out if the security system is enabled. Hence, I can't remove the radio to run diagnostic tests (such as measuring the power from the head, or drive the power amplifier to see how much power it can handle) because if the security system is set, this will leave me without a radio in the car until I get everything sorted out.

So, does anyone here know the answers?

I think i got everything here for you.

What you need to do is head over to Celicatech and check out their audio section stickies. They have a lump info thread on System 10 and the part number for the Metra harness that you need is in there. That harness will allow you to use your aftermarket head unit, with your stock amp, and retain use of all your speakers.

jiml8 · 02-03-2009, 11:35 AM

Quote:

1) Zero. The stock head has no output power. It's for signal processing only.
2) You don't power an amplifier beyond giving it a power source to draw on. (battery)
3) Doesn't matter.

Well, these are quite obviously not true.

Thanks for the link to celicatech. However the sticky there deals with wiring an aftermarket head to an aftermarket amplifier using the existing System 10 harness and speakers. So, it helps a bit in that it suggests (but doesn't state a part number) that a harness adapter is available to connect the aftermarket head to the installed harness.

It does not clear up whether the aftermarket head will properly drive the stock amplifier.

concealer404 · 02-03-2009, 01:47 PM

Quote:

Originally Posted by jiml8

Well, these are quite obviously not true.

Thanks for the link to celicatech. However the sticky there deals with wiring an aftermarket head to an aftermarket amplifier using the existing System 10 harness and speakers. So, it helps a bit in that it suggests (but doesn't state a part number) that a harness adapter is available to connect the aftermarket head to the installed harness.

It does not clear up whether the aftermarket head will properly drive the stock amplifier.

You don't "drive" an amplifier man.... You send a signal to it, and then the amplifier "drives" the speakers.

The headunit has no output power STOCK in terms of what you're talking about. It'll have an output signal power rating in volts, but not watts. And that doesn't really matter a whole lot, as it's not powering the amp anyways. Yeah, higher volts make for a cleaner signal, but it in no way will ever cause damage to the amp.

The impedence in OHMs in this case isn't a big deal. Normal is 4ohms. Considering that you're powering your speakers with an amp anyways.... the head unit doesn't even come into play, because again, it's not powering anything, so it has nothing to even measure in OHMs in terms of what it's doing at the moment. You need to worry about the impedence matching between your amp and speakers, not your headunit to amp, because the second you use the rca outputs or outputs of any kind from a head unit to an amp, you aren't even using the headunit to power anything, again.

My three statements ARE true buddy. Those are blanket statements that don't apply to just car audio, but audio in general. Anyone that tells you differently is wrong.

Go ahead and run those statement past the audio subforum here and let me know how many people tell you otherwise.

There IS a part number in those stickies for a Metra. They have it for both iterations. You need a different part number for 90-91, and 92-93. (I'd pull the part number for you, but i'm at work and can't get through to that site right now, i apologize.)

You don't need an aftermarket amplifier. You just said those stickies tell you how to use the stock harness with aftermarket head unit and aftermarket amplifier. If you're using the stock harness, why wouldn't it still go into your stock amp?

So what you need is:

1) head unit of your choice
2) metra adapter harness to go from back of your new head unit to the existing harness which will then either
3) run to your stock 5-channel amplifier or:
3.5) run to your aftermarket 5-channel amplifier.

I fail to see why the amplifier has anything to do with this, you're still using the stock wiring with the adapter.

If you don't want to do it that way, that's fine, i won't be offended, but you'll probably lose the use of your factory 8s in your door panels.

Pineapple · 02-03-2009, 05:34 PM

Dump the stock amp. Its 220W MAX for all 10 speakers or 3 pairs: Front, rear and sub. Your new deck already got more power then the "amp".

concealer404 · 02-04-2009, 09:38 AM

Quote:

Originally Posted by Pineapple

Dump the stock amp. Its 220W MAX for all 10 speakers or 3 pairs: Front, rear and sub. Your new deck already got more power then the "amp".

Err.... not so much.

The stock System 10 amp is a 4x25 plus a 2x60. And that's true power. Your average deck rated at 4x52 or whatever MIGHT bench 15w per channel, and you're still lacking two channels at that point.

Sure, go ahead and get a better amp, but that's not a part of the question of this thread.

TBayToyotaBoy · 02-01-2010, 11:00 PM

MAN am I glad this thread has popped-up now. For three days I've been trying to figure out which wire colours correlate to which functions on the harness from the oem head I just removed. Same thing, double-din CD/tape radio unit for my 91 GT-S with the System 10.

I don't want to wait for a Metra adaptor harness to come in (the shops in my town are oblivious), so I'm trying to rewire/solder to my new deck's harness. Below is a good diagram of the pigtail coming out of my old head--the top harness is mine, for the 90-91 iteration (this is courtesy of Celicatech forums):

My problem is that every colour-coding I've seen is slightly different, like this one I've found that doesn't differentiate between 90-91 and 92-93 which are different (courtesy of www.the12volt.com):

So once I figure this sh!t out, if I ever do, I'll post the results. The Metra harness looks good, but if you can't get your hands on one (or can't wait), and if you, like me, don't want to bypass the stock amp and rewire every freaking speaker, I'll post my findings. I never expected it to be so damned difficult to sort out.

--Tim

TBayToyotaBoy · 02-01-2010, 11:13 PM

One more thing: after pulling my passenger seat and amp out, I matched the harness out from amp to speakers to the BGB diagram listed on this link:

http://home.comcast.net/~jasonbuterbaugh/celica/celica92wiring.pdf

Look under the stereo wiring page for the amp wiring. Thanks to Jason on Celicatech for posting the link, but you can also find it on Celicatech's BGB section if you register as a member.

After much trouble, I matched the wiring on page 2 of that pdf to the wiring out of my head unit. The only problem is that it doesn't have a listing for wire number 8, which on my deck is white with a green stripe; and it doesn't list wire number 2, which on mine is green with silver dots. Looking on the "illumination" diagram, I see the white with green stripe leads IN to the deck, and the green leads OUT to the amp.

--Tim