head unit ground question

Eldorado · 06-19-2006, 08:05 PM

installed a new stereo head unit today and needed to search out a ground... the closest metal screw that i could use was coming out the back of the console area and screwing onto one of the 4 screws that holds the DME in the car (not the screws that hold the covers on)...

is this safe? grounding on the DME case?
my case is already grounded...

AA_Ezra · 06-19-2006, 10:06 PM

You're Radios original ground was gone? In my car I had the regular 3 power cables if i remember correctly, Red, Yelow, Black. But i had to rund a new power wire b/c the stock one was fused to low and i didtn wana risk and put a higher amped one. Reason: after a certain volume my radio cut out, cliped from to low power

For ground you could use the bracket that's way way in the back it's kinda like a stop 2 froks pointing up and it's all back you could probly use a self tap screw and tap into that. Removed mine as i needed more room.

Eldorado · 06-20-2006, 02:42 AM

my old ground was there... i just have no idea where it connects to. I cant follow that wire so i cant clean it's connection.. (if it was anything like my power cables, which looked green and fuzzy, it needed a good cleaning.)

i have the same problem... .radio cuts out after too much volume... you just replaced the red wire? i didn't see a fuse on my red wire.. there was one on my yellow wire that I cut out because there's a fuse built into my new receiver... there was also a transformer of some sort in my yellow wire that i cut out.. wasn't sure what that was there for, but it was on my old head unit's harness, not my car wiring...

Jer944 · 06-20-2006, 04:03 AM

i had a problem with my cars head unit but havent look to far into it, i cant find a constant 12v to run the memory on the radio

AA_Ezra · 06-20-2006, 08:09 AM

sorry my mistake, this refreshens my memory. The red wire is the constant ( for memory purposes). The yellow wire is the power wire the one that actualy gives the radio the juice. That's transformer looking Is probly what i think it is, It has a small fuse inside of it and it's basicaly a filter so that you don't get any alternator noise. Somewhere a while back ago I found out where the fuse was for the fuse radio line up and it was like a 10a fuse. What I did was i ran a 10gauge power cable from my battery (30a inline fuse). I actualy dirlled a hole in my firewal. after a few months i realized i could have done it differently. There a little rubber plugs right there by the Hood arms, When you remove one you should be able to run that power wire all the way down to the kick panel where the hood release is. Punch a lil hole in that rubber plug big enuff so that you can feed the power wire right threw it and be realy snug and that should take care of the radio problem if you wish to go that route.

Slam · 06-20-2006, 08:15 AM

Hey, E,

Behind your glovebox on the r/h side is a factory ground point. It's easy to get to if you take out the glovebox - 2 screws and the glovebox comes out. This spot makes a good ground for console wiring 'cause you can put in new grounds attached here and not have to go fishing under the dash.

HTH

lateapex911 · 06-20-2006, 01:16 PM

I would test the ground concept by running a heavy wire externally first.

Your head unit might be shutting down for other reasons. It might be seeing a slight short in a speaker wire, sensing imminernt or existing distortion, or it might not like the speaker load. As in too many speakers..or more than it was designed for. Or of course, it could be the power connection.

Eldorado · 06-20-2006, 01:53 PM

4 speakers... not high wattage..
i've rewired all 4 speakers.. so it wont be a short in the speaker line..

i know it's a power issue because the lights on my head unit blink when i turn the volume up high enough..

I'll try running an external power line first, just through the door, to see if that helps...

although i could be mistaken... the yellow was the constant on, and the red was the power controlled by the ign' switch.

lateapex911 · 06-20-2006, 02:10 PM

Generally, the accepted "code" is yellow constant hot to hold memory, and red for ignition.

However, the harness from manufacturers can vary. Bet idea is to go to Radio Shack and buy their $25 multi mter. IT's small and digital, and will be super in cases like these. O get a 12V test light, but that won't tell you much about whats a ground and the impedance of wires and connectors.

A great way to find grounds is to get a digital meter, set to ohms and go looking for a reading of .1 ohm when one lead is on a known good ground.

Eldorado · 06-20-2006, 02:39 PM

that's exactly what i did, jake.. only i already had the multimeter

back to my original question... is it safe to ground onto the DME case? worked fine today, but dont want to prolong it if it's a bad idea...

if it isn't smart, i'll do what slam suggests and take out the glove box..

NKN84944 · 06-20-2006, 03:56 PM

AA-Ezra that is some great input! I am actually sorting out the same problem you had with my current head unit. I replaced the fuse with a beafier one, but it did little to stop my power from cutting out at higher volumes. I am definitely going to try running a smaller gauge line to get some more juice through that hole you mentioned.

Also, on my car the ignition power is the red wire...

Eldorado - sorry I don't have an answer for you. I just used the ground wire that was there already... Maybe you can run the wire out the port that AA was mentioning and hook it up to an existing ground on the lower crossmember or in the engine bay.

AA_Ezra · 06-20-2006, 10:27 PM

My Mistake folks i get caired away some times. the yellow is the constant and the red is the Turn on/ignition. I too used the Original ground

NKN84944, It's the power source. I thought of putting a bigger fuse but kept the original one b.c i didnt want to melt anything. I just wish i woudl have put a lil more time into finding a good place to run some wire threw instead 2 holes one for my 4guage and 10guage power wire. Those lil seals will seal up great just as long as you don't make the hole to big for the wire, you want some resistance when it tries to go in. And you could probly go the extra step and put a little Silicone to make sure it's super water proof

Slam · 06-22-2006, 09:22 AM

Your deck is probably shutting donw because it's gotta push the speakers too hard. That's a self-protection feature of a lot of car stereos. Try putting in an amp and see if that helps. Many decks won't accept pushing too much voltage through speakers with too much resistance - is everything in phase? Are you correctly matching your ohm ratings?

The dash ground is an easy one. And yes, you can ground to the DME case - mounting screws for it are easy to get ot.

lateapex911 · 06-22-2006, 10:30 AM

Quote:

Originally posted by Slam
Your deck is probably shutting donw because it's gotta push the speakers too hard. That's a self-protection feature of a lot of car stereos. Try putting in an amp and see if that helps. Many decks won't accept pushing too much voltage through speakers with too much resistance - is everything in phase? Are you correctly matching your ohm ratings?

The dash ground is an easy one. And yes, you can ground to the DME case - mounting screws for it are easy to get ot.

It's actually too LITTLE resistance. Try putting an ohm meter on a speaker. Most are around 4 ohms. Now wire them in paralell, and you'll see 2. Some amps are sketchy about resistance. ) is a dead short. Head units are just not capable of getting the parts packed in such a small space, for head unit dollars.

Amps are often the only real solution.

Rmills944 · 06-23-2006, 03:41 PM

just a hint - on the Porsche and VW I have the brown shades of wires are grounds.

shikzachaser · shikzachaser's Garage

This is the one area I do know a little about. The problem is you are probably taxing the power supply in the head unit. Most mfg power specifications are optimistic at best, normally one channel driven at a specific frequency, around 1KHz (not full range) yielding relatively high numbers. They are still FTC RMS ratings, just not very accurate. Running 4 speakers w/ a fairly moderate power unit will cause the power supply voltage to dip below say 9-10 volts causing the unit to shut down momentarily. The ground is brown but probably not the problem. You should actually have a decent ground through the antenna unless it's in the windshield. If you go to a high power is-dash (the ones rated @ 40 X 4 or so) you will need to run a new primary power wire to the battery as the 18ga wire from the factory will also cause the supply to dip from too much current in too small a wire. I recently redid my 84 stereo and it sounds pretty decent for a 944.

I made 1.25 cubic foot sealed fiberglass enclosures to fit under the carpet behind the wheelwells. I used a 6X9 Polk woofer in each. I installed Polk 6X8 coaxes intended for a Mazda or Ford in the stock holes behind the seats (you don't have to take the window out like most people say). There are ADS 300i Plates in the doors. I shimmed the passenger seat up about 3/4" to allow a SONY 75W / channel amp to sit there. It is running full range to the fronts w/ the backs in parallel using passive crossovers rolling off the high frequency @ around 200Hz. The side coaxes are run off the internal amp front channels in the SONY in-dash CD. The whole thing including the head unit was under a grand with me doing the work.

I used to own Auto-Earotic in St Louis in the 80s. We did a lot of pretty high end stuff. I was the only direct Bosch (German Blaupunkt), Concord, Audiomobile, Pyle, Nakamichi, ADS dealer in the midwest. I actually had my store featured by Bosch and acted in an advisory capacity to Blaupunkt for North American marketing.
We won CES in Jan 83 and June 84 w/ my 911. It was crazy. I used 14 Audiomobile 100W / Ch Class A amps basicly filling the luggage area and the interior was removed and remade with 36 Pyle speakers. This was long before the days of the boom boxes and actually it had fairly flat response and incredible volume. This was also pre-CD. Concord and Nakamichi were the decks to use along with Mobile Fidelity 1/2 speed master cassettes. Both units had the ability to adjust head azimuth and were considered to be the thing to have.
All speakers came out and the stock interior went back in
when I sold the car. The product was comp from the various manufacturers.

I actually had a lady come up to me in Vegas at the show and start ripping me for "taking the engine out just to put in a stereo". It wasn't even worth popping the rear to show her how I drove it there.

Steve