'91 240 Radio Problems

[RUTH!]

Hi!
First, I do want to say that I've poked around here looking for an
answer to my question (which actually may have already been answered,
but I didn't see/understand it). So if this is a total repeat thing,
thank you for answering it yet again!

So, I have a '91 240 sedan whose radio has went all weird on me. The
only way I can hear anything is if I turn it up all the way. When I do
that, I hear the music really faint and there's loud buzzing on top of
the music. I thought it was the antenna (because like a dummy I left
it up, went through a carwash, and it broke), so I replaced that.
Still sounds the same. Then I thought that the whole thing was just
old and kaput since it's the original, except that one day, while I
was in traffic it came in all of a sudden crystal clear (and startled
the crap out of me) like normal. So, what gives?

I looked on here for wiring diagrams so I could check the wires
myself, but knowing pretty much nothing about my car, it made no sense
to me at all.

Help!? Please!!! I just want to listen to the radio!

Thanks a bunch,
Ruth

 

[Lane Gray, Czar Castic]

Hi!
First, I do want to say that I've poked around here looking for an
answer to my question (which actually may have already been answered,
but I didn't see/understand it). So if this is a total repeat thing,
thank you for answering it yet again!

So, I have a '91 240 sedan whose radio has went all weird on me. The
only way I can hear anything is if I turn it up all the way. When I do
that, I hear the music really faint and there's loud buzzing on top of
the music. I thought it was the antenna (because like a dummy I left
it up, went through a carwash, and it broke), so I replaced that.
Still sounds the same. Then I thought that the whole thing was just
old and kaput since it's the original, except that one day, while I
was in traffic it came in all of a sudden crystal clear (and startled
the crap out of me) like normal. So, what gives?

I looked on here for wiring diagrams so I could check the wires
myself, but knowing pretty much nothing about my car, it made no sense
to me at all.

Help!? Please!!! I just want to listen to the radio!

It sounds like a cracked trace on the circuit board of the radio, or some
other loose connection, but I've no doubt the problem lies inside the
radio. The problem might lie in a loose connection at a speaker, but then
it would need to be *each and every* speaker. Occam's Razor and all that.
Speaker connections=probable waste of time.
If you can get to the back of the radio, check for loose connections
first, as those will prove the easiest to fix (just plug it back in), but
in all likelihood, the problem is inside the radio. I don't think even a
dealer will fix a radio (they'll sell you a replacement), you might find
an electronics repair shop somewhere, or see if your local area has a
music store (I mean instruments and amps, not CDs) with a repair shop and
bring them the radio. The people who find and fix amps should probably
prove able to get this fixed, but probably not cheaply. After all,
s/he'll have to just poke and prod and play detective inside the radio,
and they deserve to get paid for that time, since once they find it,
fixing it will likely only take 30 seconds with a soldering iron.


--
Lane Gray
get the .lead out before replying (sorry for munging, I can only take so
many copies of automat)
And they were both naked, the man and his wife, and were not ashamed. Gen
2:25

 

[Tim C]

I have a '92 940 with the same problem (perhaps). I was hoping someone
would come along with a simple answer. I've also not seen a hint of
it elsewhere.

In my case, the buzzing is very clearly related to the speed of the
engine: faster RPM = slightly higher buzz pitch. At idle it's a
"clug clug clug."

It also so happens that if I turn the speakers full rear (so the
front four speakers are off) the sound goes away completely. If I
turn them ever so slightly front the sound returns in full. The
volume seems to be independent of the radio volume.

Finally, if on my morning commute I wait long enough (20 minutes
seems to do it), I can turn the speakers to the front and there is
then no more buzz, as you describe above.

I was going on the assumption that a ground was loose somewhere,
or perhaps a speaker wire was grounded into the frame.

My antenna is also broken and I've never played with it, but
I would expect that kind of problem to be impacted by the volume
of the radio dial.

I'm also toying with the idea that the alternator diodes are
going, and since I have to install a new alternator anyway I'll
let you know if that solves the problem. I don't really think
it will, but it's nice to dream that I'll fix all kinds of
problems at once.

If you can get to the back of the radio, check for loose connections
first, as those will prove the easiest to fix (just plug it back in), but

I've not done this yet; to me it's just an annoyance (and the
back speakers work) but this is probably worth a shot if you care.
(Well, and my car has ...other... problems at the moment.)

When I bought the car I was told the radio was broken, and I had
planned to get some old computer speakers and a walkman, and plug them into
an inverter. Might be worth a shot if you can't get it to work.
Otherwise if you're in the States, K-Mart and Walmart both have cheap
radios in many of their stores...

Good luck!

-TC

 

[Lane Gray, Czar Castic]

I have a '92 940 with the same problem (perhaps). I was hoping someone
would come along with a simple answer. I've also not seen a hint of
it elsewhere.

In my case, the buzzing is very clearly related to the speed of the
engine: faster RPM = slightly higher buzz pitch. At idle it's a
"clug clug clug."

Do you have AM only? Alternator whine shouldn't happen on FM or when
playing recorded media (tape or CD, or even if you've gone wierdgeeky
enough to get one of those turntables they sold for a few years in the
sixties/seventies).

It also so happens that if I turn the speakers full rear (so the
front four speakers are off) the sound goes away completely. If I
turn them ever so slightly front the sound returns in full. The
volume seems to be independent of the radio volume.

Hmm. Things get curiouser and curiouser. Almost sounds like the
alternator (or some other component, but none seem likely) put out RF,
which your front (but only the front, more curiouser still) speakers pick
up (after all, a voice coil acts like a pretty decent antenna, it has a
LOT of wire) and send backwards through your power amp section, it gets
rectified and sent back through the power amp whence it came. This sounds
like a lot of baloney, but I had it happen to me when I was younger,
playing pedal steel in my bedroom. Steel amps generally have about 300W
RMS. Ham radio operator about 70 yards from my bedroom just blew my ears
off with his call sign.
If your front speakers sit in the doors, consider a ground wire from door
to frame (the sheet metal of the door should provide adequate shielding, I
don't know why it doesn't seem to) to bleed anything off to ground.

Finally, if on my morning commute I wait long enough (20 minutes
seems to do it), I can turn the speakers to the front and there is
then no more buzz, as you describe above.

Yep. sounds more and more like alternator whine. You've charged your
battery by then from the drain of an overnight's worth of ignition-off
draw and starting, so the alternator doesnt' put out as much anymore.
Please tell me it gets markedly worse at night? If it doesn't, then I
need a new theory. Don't make me try to think of one.

I was going on the assumption that a ground was loose somewhere,
or perhaps a speaker wire was grounded into the frame.

Well, *one* wire should be. You might also have a speaker wire with
insulation worn off, making it more prone to pick up crap you don't want.

My antenna is also broken and I've never played with it, but
I would expect that kind of problem to be impacted by the volume
of the radio dial.

Right, and it would also mean you have crappy AM reception. I enjoy my AM
classic country music (I'm probably the only person around here with an
MP3 player loaded with Carl Butler, Carl Smith, Cal Smith, Connie Smith,
Sammi Smith, Johnny Bush and Darrell McCall) too much to not replace that
puppy., but yeah, that should get impacted by volume knob.

I'm also toying with the idea that the alternator diodes are
going, and since I have to install a new alternator anyway I'll
let you know if that solves the problem. I don't really think
it will, but it's nice to dream that I'll fix all kinds of
problems at once.

If your problem comes from alternator whine, then it might fix it.


--
Lane Gray
get the .lead out before replying (sorry for munging, I can only take so
many copies of automat)
And they were both naked, the man and his wife, and were not ashamed. Gen
2:25

 

[Tim C]

Hmm. Things get curiouser and curiouser. Almost sounds like the
alternator (or some other component, but none seem likely) put out RF,

draw and starting, so the alternator doesnt' put out as much anymore.
Please tell me it gets markedly worse at night? If it doesn't, then I
need a new theory. Don't make me try to think of one.

....

Anyway, the problem has been solved, and it's not at all what I
expected.

I replaced the alternator, I think (in retrospect) that it was not
_really_ the problem in the first place but it did not help the
radio.

Eventually I tracked my _starting_ problem down to a loose ground
battery connector; the symptoms:
1) I would sometimes not be able to get the car started (no crank
at all, the interior lights didn't come on);
2) I would sometimes get only a very little "whump" when I started
the car (interior lights would be on then go off), then nothing as #1;
3) I would sometimes start immediately, no problem at all, all lights on.

Incidentally, the positive terminal of the battery was always hot (in
retrospect probably the connector) and there was _lots_ of terminal
corrosion.

I replaced the battery, with the same symptoms, but eventually I
found that when I jostled the ground cable (connector was tight but
apparently the crimp was not) the car would run fine. After hitting
a variety of bumps (=one of car reset or dead car) I replaced both
connectors with a couple of screw-types from AutoZone.

Since then the radio's been perfect, as has the rest of the car
(except a possible loose ground on the dashboard? after rain but not
since it dried out...).

My only conclusion is that perhaps one of the +12 wires was loose and
was getting noisy power from somewhere else in the system. Since mine
was right at the battery connector maybe that's a place to look first...

Good luck if someone else happens to have this problem.

-TC