OT - Car Stereo Wiring Mystery

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Snarl 12/8
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OT - Car Stereo Wiring Mystery

Post by Snarl 12/8 » Tue May 12, 2009 8:41 pm

Hey Peeps,

I'm having trouble with my car stereo and I don't know where else to turn.

Last year I hit a bump in the road and my stereo went silent. The dash unit stayed on, but the amp under the seat was dead. I checked stuff out and there was 12volts on the red wire, 12 volts on the "remote" wire and the ground seemed solid. I redid everything and it still wouldn't work. So, I took it back to where I got it. They put it on the bench and it worked fine.

So today I decided to fix it and get it working again. I knew the problem must be something shaky with my cars wiring. I rewired the hot wire at the battery and made sure the wire was solid all the way to the amp. (The wiring in this car is pretty insanely DIY, so I had to be sure.) In the process of checking the wire, I somehow got it so that the stereo would power up. It works fine if I jumper the hot wire to the "remote" terminal on the amp.

The problem now is that the remote wire isn't turning on the amp any more. If I jumper from the hot it works, if I use the remote wire from the dash unit it doesn't.

I'm measuring ~12volts on the hot wire (to ground) AND 12volts on the remote wire?! I've tried hooking it directly up to the ACC wire too. It measures 12 volts with the ignition half on, but the stereo doesn't light up. I ran new wire in case it wasn't getting enough current or something, but no difference.

Does anyone know what I'm missing here? Anything else to try? I'm at my wits end, but I can't leave the amp on all the time when the car's off. I'm thinking of wiring up a switch on the jumper from hot to remote, but I know I'm going to leave it on some night and kill my battery. What does the remote terminal need besides 12volts?

Thanks,
Carl Keil

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Post by ;ivlunsdystf » Tue May 12, 2009 10:27 pm

This is kind of an off-the-wall suggestion here, but your post is totally off-topic so I guess all bets are off. Anyway, I suggest you take it someplace where car stereo installation is done for a flat fee (ie, Best Buy). Pay the fee and don't tell the dudes in the shop anything about your wiring woes. Just ask them to hook up your amp for you. (You might have to buy an amp or some speakers or something to qualify for the flat fee hookup)

Come back when they call you and watch: Chances are they won't even say anything about your weird wiring, they'll just say 'here, it's done'

I am ordinarily a hardcore DIY'er but for car stereo stuff which can be a real PITA I have had great success with this farming-out approach. the dudes who install car stereos are REALLY into car stereos and they can diagnose weird wiring stuff in their sleep ... or so I have found in my neighborhood.

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Post by Snarl 12/8 » Tue May 12, 2009 10:32 pm

;ivlunsdystf wrote:This is kind of an off-the-wall suggestion here, but your post is totally off-topic so I guess all bets are off. Anyway, I suggest you take it someplace where car stereo installation is done for a flat fee (ie, Best Buy). Pay the fee and don't tell the dudes in the shop anything about your wiring woes. Just ask them to hook up your amp for you. (You might have to buy an amp or some speakers or something to qualify for the flat fee hookup)

Come back when they call you and watch: Chances are they won't even say anything about your weird wiring, they'll just say 'here, it's done'

I am ordinarily a hardcore DIY'er but for car stereo stuff which can be a real PITA I have had great success with this farming-out approach. the dudes who install car stereos are REALLY into car stereos and they can diagnose weird wiring stuff in their sleep ... or so I have found in my neighborhood.
Yeah, obviously that's the next step.

I'm A) trying to avoid that fee
and B) trying to learn something here.

The main problem I'm having with this problem is that it is seemingly inexplicable. Everything works, except it doesn't. If I wasn't so tantalizingly close to fixing this myself, I'd probably do what you suggest. Haven't you ever gotten into something crazy and then felt like you needed to see it through?

I think I'm going to call the place I bought it from tomorrow and see if they can give me a hint. I really do respect what those guys do with car stereo installs, but I want to know the answer.
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Post by JWL » Wed May 13, 2009 10:05 am

It's possible that your amp needs more current on the remote lead than your deck is capable of delivering. This was a common problem years ago. The solution is to add a Bosch relay, have the remote lead trip the relay, which then sends 12v to the remote lead on the amp.

That said, I'm not sure why that would suddenly be a problem after hitting a bump.

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Post by T-rex » Wed May 13, 2009 4:21 pm

Well I used to install years ago, but that sounds really weird.

If you want an alternate route, you could find an accessory item in your fuse box, something that turns on when you turn the key on and run your remote wire from that.
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Post by Snarl 12/8 » Wed May 13, 2009 10:49 pm

Hey thanks for the ideas. I wasn't going to post back to this unless someone else did, since it's so OT.

I went to start my car today and it had a total conniption fit. 3 extra idiot lights were on and it was driving really rough?! (From fixing the stereo?) So I took it to a stereo place. The guy took a look at the insane DIY spagetti under the dash and told me to take it to the dealer for a diagnosis code? Turns out I had a bad Air Mass Flow Sensor. I fixed that and the car is running good again and the idiot lights went out after clearing the code.

But the stereo is still doing that weird thing. I really think that there's something wrong with the amp. Unfortunately, it was almost out of warranty when I took it in to be checked and then I waited all winter. I'm going to take it to the pro installer people this weekend. Fuck it. I've learned enough from this debacle, I need to get back to making music.

I think I'm also going to take the car in somewhere and have ALL the stereo and alarm wiring ripped out and put in correctly. It'll probably be $3-400 or something, but I can't take riding around in an electrical house of cards.

Thanks again.
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Post by TapeOpAl » Sun May 17, 2009 6:20 am

If you haven't gone the pro-route already, ask over at

http://www.talkaudio.co.uk/vbb/

It's a UK car audio forum with a lot of knowledgeable people - if you let them know what gear you have I'm sure they'll help you out.

You should have:
+12V and ground to your head unit (stereo)
+12V and ground to your amp
A remote cable from your stereo to your amp
RCA audio cables from your stereo to your amp
Speaker cables from your amp to your speakers.

If the amp has power and the head unit has power the only reason the amp should not turn on would be it's not seeing an adequate remote voltage (could be none at all.) Check the manual for your amp and see what it's expecting to see and then get a multimeter and check what the headunit is sending out. That should tell you which side the fault is on.

Wiring is simple but can be fiddly to physically run the cables. If you want to rewire I would recommend:

Run a new power cable from your battery through the firewall in the engine bay - there should be a rubber grommet for existing cables that you can (carefully) punch a hole through. I got 4AWG cable through one in my old car so you should be fine. If there isn't one, drill a hole of your own into the passenger footwell and use your own grommet (essential so the metal doesn't cut through the cable and short out).

You absolutely must use an inline fuse at most 6" from the battery. The size of the fuse depends on the size of your amp - don't use one too big.

Now get a distribution block and do a +12v cable run to the amp and one to the head unit.

Find a grounding point on the chassis of the car and connect the amp and head unit to it (both to the same one) - scrape off the paint to get a good connection with the metal. Attach ring connectors to the cables and cover the bolt with grease to stop rusting.

Your existing remote, audio and speaker cables should be reasonably tidy so it's job done from here.

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Post by Piotr » Sun May 17, 2009 11:11 pm

Who cares which unit is powering what? If you're drawing enough juice at both ends just get your audio going. And who cares? Your car sounds super sketchy (no offense!) and may not be worth the effort?
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Post by Snarl 12/8 » Mon May 18, 2009 1:10 am

Piotr wrote:Who cares which unit is powering what? If you're drawing enough juice at both ends just get your audio going. And who cares? Your car sounds super sketchy (no offense!) and may not be worth the effort?
Actually, I care, because I have it all hooked up "correctly" and it's still not working, so I'm at the level of having to troubleshoot components. My car is not really that sketchy at all, but its electrical system is pretty well and truly fucked, but I'm not ready to throw the baby out with the bathwater just yet.
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Post by Judas Jetski » Sun May 24, 2009 8:43 am

If it was me, I'd take it to a shop.

*deletes long rambling post about years spent chasing a variety of electrical problems around a variety of old cars*

It's way better to get the thing so it works right. That way you have a good baseline to work from when it's time to customize stuff.

EDIT (*re-inserts key component deleted with long rambling post*): Everything may be hooked up correctly from your perspective. But if some earlier owner hooked something up incorrectly, your correct wiring might be doing something incorrect.
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Post by Judas Jetski » Sun May 24, 2009 8:49 am

Also, check your grounds. On everything. Ev. Ery. Thing. The stereo. The speakers. The battery. The brake lights. The little light so you can see what gear it's in. The fan motor. The cigarette lighter. Everything.

Grounding problems are evil, I tells ya, EEEEEEEVVVVVIIILLLLLLLLL!!!!!!!!!!!!
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Post by Snarl 12/8 » Sun May 24, 2009 11:45 am

I really should post a pic of the underside of the dashboard. It makes that spagetti that's behind some people's mixers look like good cable management. I mean at least with that stuff you can usually see both ends of the cable.
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Post by Judas Jetski » Mon May 25, 2009 5:09 am

What kind of car is it?
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Post by Snarl 12/8 » Mon May 25, 2009 8:36 am

Scion xB - the original "toaster" model.
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Post by TapeOpAl » Mon May 25, 2009 12:18 pm

Snarl 12/8 wrote:I really should post a pic of the underside of the dashboard. It makes that spagetti that's behind some people's mixers look like good cable management. I mean at least with that stuff you can usually see both ends of the cable.
The way I suggested hooking it up above would bypass all of your cars wiring and is the shortcut to finding out what's working and what's not as far as your audio is concerned.

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