1995 Corolla Wiring Question - Pre-1997 Toyota Corolla and Geo Prizm

I bought another radio to replace the factory installed one. I also bought a wiring harness to connect the aftermarket radio to the factory wiring. I followed the directions, connected the corresponding wires from the new radio to the harness and then plugged it in to the factory wiring. I connected the antenna and turned the car on. I had power to the radio, but no sound from the speakers. Is there something I am overlooking? The radio had no negative speaker wire, just the positive ones. It had a ground wire, but I hooked that to the wiring harness' ground thinking that the factory wiring was grounded to the car itself. Should I have connected the ground wire from the radio to the metal in the dashboard? As you can tell, I'm new to this installing thing, but the pros charge way too much. I figured I could muddle through somehow! Any tips are greatly apprecitated

I haven't seen too many headunits use a single signal wire for each speaker - tying to a common ground is a sure fire way to pickup electrical noise. Usually, if a headunit actually has two signal wires per channel, and you accidentally ground the "negative" side, you will immediately cook the amplifier stage.

Anyway - there should be a lug on the back or side of the headunit that will allow you to ground the radio itself. I'm assuming that you unplugged the negative battery terminal before you unplugged/plugged in anything in the dash - if not, you could have cooked a fuse or relay in the car or worse, in the headunit you just bought.

Would be helpful if you mentioned the brand and model number of the headunit - might get a few more people to chime in on it or offer their experience (good or bad) with the unit in question. Also assuming that the headunit is able to drive the speakers in question, ie. you have correctly matched speaker impedance and minimum power requirements?

Bikeman982

I have used universal adapter wiring kits to put aftermarket radios/CD players in my cars.

I have a couple left over, if you would like to purchase it.

I guess you get what you pay for. The head unit is a Pyramid 2702D. I have a beat up Corolla and didn't want to a "good" stereo in there. I was looking for a cheap replacement for the factory stereo. The reason I bought the Pyramid was, it was cheap, and it had and AUX input for my IPOD(I have used FM transmitters and the cassette adapters, I wanted to try a more direct connect without having to fork over a couple hunderd for a direct connect to a expensive stereo. I have one thing to try. This head unit is only 40 watts x 2. I was hoping that I could still get sound out of all 4 speakers 20 watts each? I don't think this unit can handle that. I hooked up the connections for the front 2 speaker on the aftermarket harness and will try it again tomorrow. I suspect it doesn't have enough to do what I want it to do. By the way, I spent less than $20.00 on the stereo!

Thanks for your input.

OK - I see now.

Definitely try and see if you can drive the two front speakers alone - could have ended up with a bum amplifier section - not completely unheard of. I've had quite a few units be bad, right out of the box, a large percentage usually do to shipping damage.

Trying to run 4 speakers from a channel headunit - might be possible. Chances are, the headunit cannot drive that impedance of two speakers wired together like that. You can wire the speakers in parallel or series - parallel will generally drop the overall resistance of the circuit (will halve the impedance of a single speaker, assuming that the speakers all have the same impedance). Hook the speakers up in series - the impedance will be the sum of the speakers in the circuit. Most headunits will put a rating on what they would be able to drive - impedance wise.

If you are trying to drive OEM speakers - this might be possible - assuming that you really have 40w a channel. Some manufactuers list P-P or peak-to-peak power, which looks good on paper, but means very little to drive the speakers. Especially if you reference the speakers to ground - given 40w p-p, you are looking at around 14w total per channel. Could be even a bit less. I believe my OEM headunit (Pioneer or Fujistu-10/Eclipse) was rated at 10wx4 continous or around 30wx4 ot 40wx4 peak.

OK - I see now.
Definitely try and see if you can drive the two front speakers alone - could have ended up with a bum amplifier section - not completely unheard of. I've had quite a few units be bad, right out of the box, a large percentage usually do to shipping damage.
Trying to run 4 speakers from a channel headunit - might be possible. Chances are, the headunit cannot drive that impedance of two speakers wired together like that. You can wire the speakers in parallel or series - parallel will generally drop the overall resistance of the circuit (will halve the impedance of a single speaker, assuming that the speakers all have the same impedance). Hook the speakers up in series - the impedance will be the sum of the speakers in the circuit. Most headunits will put a rating on what they would be able to drive - impedance wise.
If you are trying to drive OEM speakers - this might be possible - assuming that you really have 40w a channel. Some manufactuers list P-P or peak-to-peak power, which looks good on paper, but means very little to drive the speakers. Especially if you reference the speakers to ground - given 40w p-p, you are looking at around 14w total per channel. Could be even a bit less. I believe my OEM headunit (Pioneer or Fujistu-10/Eclipse) was rated at 10wx4 continous or around 30wx4 ot 40wx4 peak.

I tried hooking up just the front left and right speakers and didn't get sound. I took one of the front door speakers out and hooked it up directly to the head unit. That time I heard the radio loud and clear. I hooked up the positive speaker wire and negative ground wire to that speaker. When I use the harnesses, I hook up the negative ground wire from the radio to the negative ground wire on the aftermarket harness.

My factory radio runs all 4 speakers. I bought the two rear and front seperately. The original speakers were old and worn out. Does that still sound like a problem with impedence? The front speakers are just replacement cones. The rear are from Best Buy and were on clerance, but a named brand (can't remember the name).

What should my next course of action be?

Impedance could still be an issue - the headunit should have a range of impedances that you can run. The speaker impedance is silk-screen, printed, or stamped right on the magnet or basket of the speaker. To rule out simple things - check that each speakers rated impedance and polarity. The speakers should have them marked, or if not, there should be a noticeable different in the size of the speaker terminals - one should be much larger than the other - that is usually the "positive" side. You can also test polarity with a 9V battery or similar (some recommend a smaller battery, just becareful either way) - just get a couple of jumper leads to connect to the battery and the speaker leads - then very briefly touch the speaker leads. You should see the speaker cone "pump" - if movement is outward - then the polarity of the battery should match the polarity of the speaker.

I would try running the speakers directly from the headunit first - to rule out any impedance mismatch issues and to make sure that the headunit has enough juice to do what you want. If it works fine in that case - run through the wiring harness and test it again. If the speakers are not working - you could have at least one of the speaker output wires wired wrong or the harness has a broken wire/bad connection in it. Possible that one of the channels is overloading and causing the headunit to automatically cut power to the amplifier stage. Most cases, you have to cyclec power to the headunit to get it back.

Here is a link to the typical wiring color code that most Toyotas use. Just to cross-check the install instructions on the wiring harness - as I have found that they could be off from time to time.

http://www.installdr.com/Harnesses/Toyota-Wiring.pdf

Also and install PDF on the 8th gen Corolla - should be very close to other models.

http://www.installdr.com/InstallDocs/Toyota/PDF/869001.pdf

Bikeman982

You can try (by experimentation) connecting the speaker wires in different combinations.

The worst that would happen is that a fuse would burn out (have extras).

I sometimes get my car speakers working that way, when I don't have a schematic for my stereo and am not sure where the wires connect.

Hope this helps.

You can try (by experimentation) connecting the speaker wires in different combinations.The worst that would happen is that a fuse would burn out (have extras).

I sometimes get my car speakers working that way, when I don't have a schematic for my stereo and am not sure where the wires connect.
Hope this helps.

I am going to have one more go at it tomorrow. I want to try the rear speakers only. I think the head unit does not have enough power to send out the positive signal and receive the negative signal back from the speakers to complete the circuit. It obviously has enough to power the little speaker when I connect it directly to the radio itself. However, that is a long way from having the signal travel down the harness wires. I didn't find any impedence range on the radio itself.

I think this will be my final attempt. Next time, I won't buy such a cheap head unit and I will save myself the frustration. It just wasn't a high priority at this time. Oh well, live and learn. Thank you for all your input, again.