Need HELP with 2002 Mustang in-dash Radio Power Issues

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MS - 01 Sep 2005 22:23 GMT

When the car heats up under the sun the in-dash radio works fine but when it
cools down the radio will not power up. I tried replacing fuse check the
wire harness etc. but can resolve this issue. Any advice will be highly
appreciated.

Thanx.

Please drop me a line at vocalglobe//at\\hot mail//dot\\com
(remove the //\\)

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ironrod - 03 Sep 2005 17:34 GMT

Where do you live? In extremely cold conditions transistors & IC's can
become "Cold Soaked" that is, the components have become so cold that their
internal resistance has risen to the point that they can no longer conduct
electricity.

> When the car heats up under the sun the in-dash radio works fine but when it
> cools down the radio will not power up. I tried replacing fuse check the
[quoted text clipped - 5 lines]
> Please drop me a line at vocalglobe//at\\hot mail//dot\\com
> (remove the //\\)

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David M - 04 Sep 2005 02:37 GMT

> Where do you live? In extremely cold conditions transistors & IC's can
> become "Cold Soaked" that is, the components have become so cold that their
> internal resistance has risen to the point that they can no longer conduct
> electricity.

Ummm... where did you get that information from? Oh, I see,
you pulled it from your a**.

Electrical resistance of metals and most semiconductors
goes DOWN with temperature, not up.

Commercial semiconductors will perform within specifications
from 0-70C. Industrial rated semiconductors will perform
within specifications from -40 to 85C; automotive electronics
should operate within that range.

More likely the problem is a bad connection on the unit.

>> When the car heats up under the sun the in-dash radio works fine but when
> it
[quoted text clipped - 6 lines]
>> Please drop me a line at vocalglobe//at\\hot mail//dot\\com
>> (remove the //\\)

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ironrod - 05 Sep 2005 08:05 GMT

Well lets see, I've been pushing 'trons through wires for almost 30 years
now, so I'm reasonably confident that I've got the basics right. In
extremely cold conditions, approaching absolute zero, resistance drops to
near nothing. In the real world the hotter the junction of the semi-
conductor the greater the current flow. Conversely, the lower the
temperature the less current flow across the junction. Now in the real
world there is a condition designers have to deal with called "thermal
runaway" and it is a real problem in high powered circuits that get too
warm. Basically the higher the current the hotter the junction, the hotter
the junction the higher the current flow. Without any checks in place the
device will get so hot it melts. The most simple solution, of course, is to
limit the output of the power supply. No matter how hot the junction gets
it can't flow any more current than the power supply can output. Now jump
to the other half of the spectrum where the junctions are abnormally cold.
Your power supply with its limited current might not be capable of
generating enough power to meet the greater demand caused by the colder
junctions.

Now while semi conductors are capable of operating across a wide range of
temperatures, the device itself might not be. Most electronic devices are
designed to operate at "room temperature". Devices that are intended to be
used in extreme conditions are built much differently. In some cases, I've
seen environmental design problems where the best solution was to create an
artificial environment and use "off the shelf" components.

Now, you never did mention if you lived in a cold climate or not, if you
don't then obviously the problem can't be cold soaking. If you do,
re-create the conditions where the radio doesn't work, power it up and wait.
Even under the coldest conditions there will be some limited current flow
which should cause the electronics to warm up and begin to work. Also, you
might try re-creating the problem and then using a space heater to warm the
interior of the car.

> > Where do you live? In extremely cold conditions transistors & IC's can
> > become "Cold Soaked" that is, the components have become so cold that their
[quoted text clipped - 24 lines]
> >> Please drop me a line at vocalglobe//at\\hot mail//dot\\com
> >> (remove the //\\)

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David M - 05 Sep 2005 13:19 GMT

> Well lets see, I've been pushing 'trons through wires for almost 30 years
> now, so I'm reasonably confident that I've got the basics right. In
[quoted text clipped - 5 lines]
> runaway" and it is a real problem in high powered circuits that get too
> warm.

That's a different mechanism... the increased temperature knocks more
electrons loose from the semiconductor. OK, technically I guess that
would qualify as "lower resistance" (at least at your meter test points).

> Now jump to the other half of the spectrum where the
> junctions are abnormally cold. Your power supply with its limited
> current might not be capable of generating enough power to meet the
> greater demand caused by the colder junctions.

But that would not occur unless the
temperature is decades below zero.

>Most electronic
> devices are designed to operate at "room temperature". Devices that are
> intended to be used in extreme conditions are built much differently. In
> some cases, I've seen environmental design problems where the best
> solution was to create an artificial environment and use "off the shelf"
> components.

Most automotive electronics is designed to handle a much wider range
of temperature than consumer electronics.

> Now, you never did mention if you lived in a cold climate or not, if you
> don't then obviously the problem can't be cold soaking.

I'm not the OP. But I would still suspect a simpler solution,
like a loose connector contact (heating up and expanding).
Connectors have a higher failure rate than semiconductor
junctions.

>> > Where do you live? In extremely cold conditions transistors & IC's
>> > can become "Cold Soaked" that is, the components have become so cold
[quoted text clipped - 36 lines]
>> T/S 53
>> sled351 Linux 2.4.18-14 has been up 36 days 22:54

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ironrod - 05 Sep 2005 18:25 GMT

Now you begin to see the difference between a tech (me) and the engineer.
Because car radios have to live in the enclosed environment of a car,
complete with their heat catching, solar panel, greenhouse glass window
arrangement, things getting to hot are much more likely to occur than things
getting to cold, (which could only happen during certain times of the year
in certain geographic locations.) Heat rejection would be a design priory,
whereas cold performance would be just an afterthought. I agree that cold
soak probably isn't the most likely cause, however the symptoms given by the
OP were a text book example of the phenomenon. Which is why my first
question was, 'were did he live?'.

You stated "But that [cold soak]would not occur unless the temperature is
decades below zero." This isn't necessarily true, remember most IC's
operate at 5 volts, every time you cross a junction you drop between .2 to
.5 volts, it would only take a very slight increase in resistance of several
components before the overall load was so great that 5 volts wasn't enough
to get the job done anymore.

Here is an interesting test, if you live in one of the colder areas of the
country. Take a cheep transistor radio, place it inside a plastic bag then
leave it outside, in the shade, overnight when the temperature is expected
to drop below zero. Turn it on and count the seconds from when you hit the
switch until it starts playing.

> > Well lets see, I've been pushing 'trons through wires for almost 30 years
> > now, so I'm reasonably confident that I've got the basics right. In
[quoted text clipped - 76 lines]
> >> T/S 53
> >> sled351 Linux 2.4.18-14 has been up 36 days 22:54

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David M - 06 Sep 2005 00:04 GMT

> You stated "But that [cold soak]would not occur unless the temperature is
> decades below zero." This isn't necessarily true, remember most IC's
> operate at 5 volts, every time you cross a junction you drop between .2 to
> .5 volts, it would only take a very slight increase in resistance of several
> components before the overall load was so great that 5 volts wasn't enough
> to get the job done anymore.

Hmmm... I guess you haven't heard of IC's with half
a million gates and operating at 3.3V (like the CPU in your computer).
The junctions in an IC for the most part are not in series.
And they are most definitely not all forward-biased.

The I/V relationship of a forward-biased doped PN junction in silicon is
an exponential relationship that also has a temperature dependance, unlike
a resistor which is a linear relationship.
I is proportional to exp(V *(q/kT) - 1)
where q = charge of an electron and k = Boltzman's constant,
T= temperature in degrees K. Room temperature (25C) is 298K.
Cutting the temperature in half (149K or -124C or -191F)
theoretically drops the PN junction turn-on voltage by a
factor of ln(1/0.5) = .69 Assuming you could actually
get that cold, a 0.7V junction would actually be
turning on at more like 0.4V. At -50F (227K) the
change is less than 0.2V.

> Here is an interesting test, if you live in one of the colder areas of the
> country. Take a cheep transistor radio, place it inside a plastic bag then
> leave it outside, in the shade, overnight when the temperature is expected
> to drop below zero. Turn it on and count the seconds from when you hit the
> switch until it starts playing.

Can't do it, since it doesn't get down to -191 degrees here.

>> > Well lets see, I've been pushing 'trons through wires for almost 30
> years
[quoted text clipped - 78 lines]
>> >> T/S 53
>> >> sled351 Linux 2.4.18-14 has been up 36 days 22:54

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MS - 07 Sep 2005 03:48 GMT

Thanx all for replying. I live in Texas where its in 100s now. The Radio
will only power up in extreme heat. I just dont get it. Checked wiring
harness and fuses no issues there still in normal temp the radio just will
not power until in extreme heat. Any suggestion will be much apprerciated.

> When the car heats up under the sun the in-dash radio works fine but when
> it
[quoted text clipped - 6 lines]
> Please drop me a line at vocalglobe//at\\hot mail//dot\\com
> (remove the //\\)

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I. Care - 07 Sep 2005 04:41 GMT

> Thanx all for replying. I live in Texas where its in 100s now. The Radio
> will only power up in extreme heat. I just dont get it. Checked wiring
[quoted text clipped - 11 lines]
> > Please drop me a line at vocalglobe//at\\hot mail//dot\\com
> > (remove the //\\)

You might try asking on rec.audio.car.

I would try powering it from a 12v power supply and following the power
bus. Use a heat gun and gingerly heat small areas until it works, then
use a circuit cooler spray to cool it off in various areas until I could
reliably make it start and stop.

Sounds like a poorly solder connection somewhere such that the
conductors move/expand connecting when hot. That type of problem is
more common than you might think. I used to see it at times when I was
working in electronics. Especially component leads going through a
soldered connection hole in a circuit board. The connection visually
looked fine but when moved with an insulated tool or heated and cooled
as I described would fail.

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