Strange voltage drop on remote turn-on wire

[Chi]

Car: 1991 Audi 200
HU: Aiwa cdc mp3
Amp: usacoustics usx4065

After wiring up my new audio system I discovered the amp in the trunk
doesn't want to turn on. Tracked it down to the remote turn-on wire
which registers 12.2 volts with nothing attached to it, but as soon as
I attach my amp to it the voltage drops to 4.5v which is not enough to
turn on my amp.

Prior to this, I was experiencing intermittant amp power on my old amp
which I thought was being caused by the antenna booster which I wired
in parallel to the HU remote turn on along with the old amp. Wired in
a new amp (that I got for my birthday) and it turned on ok but had
horrendous ground loop noise.

I figured it was too much resistance in the 24awg wire I was using to
run back to the trunk (antennae booster is not connected) which had 3
butt connectors in it and several different wires. But when I replaced
it with a single 16awg wire it does the same thing.

If I jumper the 12v and remote posts on the amp it does turn on so I
think that my 4 year old Aiwa HU is not performing at 100% anymore.

Could this be a symptom of poor head unit ground?

I plan on using a relay to send 12v from the battery to the amp but
have to go look for a spare relay in my parts bin. Hopefully the HU
is making enough power to trigger the relay.

thanks for looking!

Chi

[Scott Gardner]

It certainly sounds like either the amp is drawing too much current at
the remote turn-on input, or the output resistance at the head unit is
too high. You've ruled out the wiring, since a 16-awg wire didn't
cure it.

The only other thing I would suggest would be to measure how much
current is being drawn by the remote turn-on input on the amp. It
shouldn't be much, certainly less than a 1/2-ampere or so. If it's
drawing excessive current, that could cause a voltage drop at the head
unit's remote turn-on output.

Scott Gardner

On 25 Apr 2004 15:05:01 -0700, (Chi) wrote:

>Car: 1991 Audi 200
>HU: Aiwa cdc mp3
>Amp: usacoustics usx4065
>
>After wiring up my new audio system I discovered the amp in the trunk
>doesn't want to turn on. Tracked it down to the remote turn-on wire
>which registers 12.2 volts with nothing attached to it, but as soon as
>I attach my amp to it the voltage drops to 4.5v which is not enough to
>turn on my amp.
>
>Prior to this, I was experiencing intermittant amp power on my old amp
>which I thought was being caused by the antenna booster which I wired
>in parallel to the HU remote turn on along with the old amp. Wired in
>a new amp (that I got for my birthday) and it turned on ok but had
>horrendous ground loop noise.
>
>I figured it was too much resistance in the 24awg wire I was using to
>run back to the trunk (antennae booster is not connected) which had 3
>butt connectors in it and several different wires. But when I replaced
>it with a single 16awg wire it does the same thing.
>
>If I jumper the 12v and remote posts on the amp it does turn on so I
>think that my 4 year old Aiwa HU is not performing at 100% anymore.
>
>Could this be a symptom of poor head unit ground?
>
>I plan on using a relay to send 12v from the battery to the amp but
>have to go look for a spare relay in my parts bin. Hopefully the HU
>is making enough power to trigger the relay.
>
>thanks for looking!
>
>Chi

[MZ]

It's probably not the best idea to power your FM booster from your remote
output. Hopefully it didn't damage your deck. As Scott said, measure the
current draw by the amp alone (simply connect both leads of a meter to the
remote and power terminals of the amp, and make sure the meter is in current
mode). It should probably be in the 100mA or less range. If it's
significantly more than that, then that could be the source of your trouble.

But my guess is that it's the head unit at fault.

--
Mark
remove "remove" and "spam" to reply


"Chi" > wrote in message
m...
> Car: 1991 Audi 200
> HU: Aiwa cdc mp3
> Amp: usacoustics usx4065
>
> After wiring up my new audio system I discovered the amp in the trunk
> doesn't want to turn on. Tracked it down to the remote turn-on wire
> which registers 12.2 volts with nothing attached to it, but as soon as
> I attach my amp to it the voltage drops to 4.5v which is not enough to
> turn on my amp.
>
> Prior to this, I was experiencing intermittant amp power on my old amp
> which I thought was being caused by the antenna booster which I wired
> in parallel to the HU remote turn on along with the old amp. Wired in
> a new amp (that I got for my birthday) and it turned on ok but had
> horrendous ground loop noise.
>
> I figured it was too much resistance in the 24awg wire I was using to
> run back to the trunk (antennae booster is not connected) which had 3
> butt connectors in it and several different wires. But when I replaced
> it with a single 16awg wire it does the same thing.
>
> If I jumper the 12v and remote posts on the amp it does turn on so I
> think that my 4 year old Aiwa HU is not performing at 100% anymore.
>
> Could this be a symptom of poor head unit ground?
>
> I plan on using a relay to send 12v from the battery to the amp but
> have to go look for a spare relay in my parts bin. Hopefully the HU
> is making enough power to trigger the relay.
>
> thanks for looking!
>
> Chi

[Richard G. Pecoraro]

One thing you can do, assuming it's not an amp problem, is use the remote
turn on wire to activate a relay (powered by 12V from a beefier circuit,
wiper blades maybe) that will then turn on the amp/amps. I use this method
to activate 4 amps in my car.

You can get a relay at any auto parts store.
"Scott Gardner" > wrote in message
...
> It certainly sounds like either the amp is drawing too much current at
> the remote turn-on input, or the output resistance at the head unit is
> too high. You've ruled out the wiring, since a 16-awg wire didn't
> cure it.
>
> The only other thing I would suggest would be to measure how much
> current is being drawn by the remote turn-on input on the amp. It
> shouldn't be much, certainly less than a 1/2-ampere or so. If it's
> drawing excessive current, that could cause a voltage drop at the head
> unit's remote turn-on output.
>
> Scott Gardner
>
> On 25 Apr 2004 15:05:01 -0700, (Chi) wrote:
>
> >Car: 1991 Audi 200
> >HU: Aiwa cdc mp3
> >Amp: usacoustics usx4065
> >
> >After wiring up my new audio system I discovered the amp in the trunk
> >doesn't want to turn on. Tracked it down to the remote turn-on wire
> >which registers 12.2 volts with nothing attached to it, but as soon as
> >I attach my amp to it the voltage drops to 4.5v which is not enough to
> >turn on my amp.
> >
> >Prior to this, I was experiencing intermittant amp power on my old amp
> >which I thought was being caused by the antenna booster which I wired
> >in parallel to the HU remote turn on along with the old amp. Wired in
> >a new amp (that I got for my birthday) and it turned on ok but had
> >horrendous ground loop noise.
> >
> >I figured it was too much resistance in the 24awg wire I was using to
> >run back to the trunk (antennae booster is not connected) which had 3
> >butt connectors in it and several different wires. But when I replaced
> >it with a single 16awg wire it does the same thing.
> >
> >If I jumper the 12v and remote posts on the amp it does turn on so I
> >think that my 4 year old Aiwa HU is not performing at 100% anymore.
> >
> >Could this be a symptom of poor head unit ground?
> >
> >I plan on using a relay to send 12v from the battery to the amp but
> >have to go look for a spare relay in my parts bin. Hopefully the HU
> >is making enough power to trigger the relay.
> >
> >thanks for looking!
> >
> >Chi
>

[MZ]

> One thing you can do, assuming it's not an amp problem, is use the remote
> turn on wire to activate a relay (powered by 12V from a beefier circuit,
> wiper blades maybe) that will then turn on the amp/amps. I use this
method
> to activate 4 amps in my car.

This is assuming the head unit is not at fault. Most relays draw more
current from the remote wire than a single amp will. This is why he first
needs to identify which component is the problem.

[Scott Gardner]

On Sun, 25 Apr 2004 19:17:58 -0400, "MZ"
> wrote:

>> One thing you can do, assuming it's not an amp problem, is use the remote
>> turn on wire to activate a relay (powered by 12V from a beefier circuit,
>> wiper blades maybe) that will then turn on the amp/amps. I use this
>method
>> to activate 4 amps in my car.
>
>This is assuming the head unit is not at fault. Most relays draw more
>current from the remote wire than a single amp will. This is why he first
>needs to identify which component is the problem.
>

Yep, the standard Bosch-type automotive relay draws anywhere from
90-160mA to activate the relay. If the problem is with his head
unit, and the head unit can't turn on an amplifier, it probably won't
be able to reliably activate a relay either.

Scott Gardner

[Chi]

Can someone help me with my current measurement?

When I set my cheap digital multimeter to 10Amps I get a reading from
the amp's remote turn on of .01 (by touching the 12v post with one end
and the remote turn on post with the other end)

When I put the meter on the 200m range I get a 13.6 reading.

Does this sound like a normal current draw for a remote turn on?

thanks in advance!

Chi


Scott Gardner > wrote in message >...
> It certainly sounds like either the amp is drawing too much current at
> the remote turn-on input, or the output resistance at the head unit is
> too high. You've ruled out the wiring, since a 16-awg wire didn't
> cure it.
>
> The only other thing I would suggest would be to measure how much
> current is being drawn by the remote turn-on input on the amp. It
> shouldn't be much, certainly less than a 1/2-ampere or so. If it's
> drawing excessive current, that could cause a voltage drop at the head
> unit's remote turn-on output.
>
> Scott Gardner

[MZ]

I don't know what meter you have, but .01 in the 10A mode probably refers to
..01A, and 13.6 in the 200m mode refers to 13.6 mA. Since 0.01A = 10mA, the
two measurements are in agreement.

In other words, if your meter is correct, your amp isn't the culprit here.
It's your head unit.

--
Mark
remove "remove" and "spam" to reply


"Chi" > wrote in message
om...
> Can someone help me with my current measurement?
>
> When I set my cheap digital multimeter to 10Amps I get a reading from
> the amp's remote turn on of .01 (by touching the 12v post with one end
> and the remote turn on post with the other end)
>
> When I put the meter on the 200m range I get a 13.6 reading.
>
> Does this sound like a normal current draw for a remote turn on?
>
> thanks in advance!
>
> Chi
>
>
> Scott Gardner > wrote in message
>...
> > It certainly sounds like either the amp is drawing too much current at
> > the remote turn-on input, or the output resistance at the head unit is
> > too high. You've ruled out the wiring, since a 16-awg wire didn't
> > cure it.
> >
> > The only other thing I would suggest would be to measure how much
> > current is being drawn by the remote turn-on input on the amp. It
> > shouldn't be much, certainly less than a 1/2-ampere or so. If it's
> > drawing excessive current, that could cause a voltage drop at the head
> > unit's remote turn-on output.
> >
> > Scott Gardner

[Scott Gardner]

When you took the measurement, was the turn-on wire disconnected?
Checking the current between the +12V post and the remote post is
valid, as long as there wasn't anything else connected to the turn-on
post at the time. If the head unit's remote lead was still connected
to the amp, and the head unit was turned on, the current between the
head unit and the amp wouldn't have been detected by the meter.

Otherwise, I agree with Mark that 13.6 mA seems like a good reading.
In that case, it sounds like something is wrong with the remote
turn-on output of the head unit. It probably wouldn't be financially
worth it to have the head unit repaired, and if the head unit can't
support 13 mA to turn on the amp, it's probably not going to be able
to power a relay, either. Perhaps you could connect the turn-on post
of the amp to a switched 12V wire. This way, your amp would be
powered on whenever your car is running, but at least you could be
sure of getting enough voltage to turn on the amp.

Scott Gardner


On 27 Apr 2004 19:28:40 -0700, (Chi) wrote:

>Can someone help me with my current measurement?
>
>When I set my cheap digital multimeter to 10Amps I get a reading from
>the amp's remote turn on of .01 (by touching the 12v post with one end
>and the remote turn on post with the other end)
>
>When I put the meter on the 200m range I get a 13.6 reading.
>
>Does this sound like a normal current draw for a remote turn on?
>
>thanks in advance!
>
>Chi
>
>
>Scott Gardner > wrote in message >...
>> It certainly sounds like either the amp is drawing too much current at
>> the remote turn-on input, or the output resistance at the head unit is
>> too high. You've ruled out the wiring, since a 16-awg wire didn't
>> cure it.
>>
>> The only other thing I would suggest would be to measure how much
>> current is being drawn by the remote turn-on input on the amp. It
>> shouldn't be much, certainly less than a 1/2-ampere or so. If it's
>> drawing excessive current, that could cause a voltage drop at the head
>> unit's remote turn-on output.
>>
>> Scott Gardner