'99 Gr Caravan Radio Garbles

[nickbuol]

About a year ago, while driving on a long trip, the Infinity radio/CD/cass in our Grand Caravan started producing garbled sound out of the front driver side speaker. This pretty much only happens with pushing the gas pedal. If I push on the gas, it garbles, if I let off, it stops.

This has since spread to all of the speakers to some degree. I finally went out and bought a new (aftermarket) radio. I installed it this week and guess what, the audio is still garbled.

Everything performs just fine when up to speed or idling, but when speeding up I loose clarity and it gets garbled sounding.

Obviously, it doesn't seem to be the radio. What can I check? I would like to take the new radio back and get a refund if I can fix the problem and use the Infinity radio. It also seems like the speakers are just fine as things work whenever I am not speeding up.


PLEASE HELP!

Nick
[email protected]

[Three_Fingers]

If you're referring to RADIO reception- check the antenna ground where it mounts to the body. The acceleration may be just enough force to move/break that ground connection until you let off the throttle and it returns to normal.
See if your ant. mount is loose/corroded.
A failing/noisy voltage regulator in the alternator circuit can also cause harmonics/noise that will garble radio audio.
Vibrations at a specific frequency can affect how speakers respond. (That's after all how they work).

[nickbuol]

It doesn't matter if it is the radio or CD (or cassette). They all act the same, so it isn't the antenna (good thinking though)...

It also doesn't seem to be a vibration issue as it will do it with people talking and any variety of music at any volume level.

Someone else (in this forum) posted a note about something with fuse #5 and putting foil in its place. That message was then removed about 5 minutes later. I believe that fuses are there for a reason, so I didn't like that answer much.

Which leaves me with your voltage regulator idea...

How would I test such a thing and how would I fix it if that is the case?

Thanks 3-fingers....

[calgary_redneck]

Lol you doing well if you have a caravan and the radio is your only problem

[nickbuol]

Don't worry. We have the classic transmission problems too.

[Three_Fingers]

OK, the voltage regulator for the radio/CD/Whatever unit is internal to the unit.
It would help if you could gimme a better description of 'garbled' audio.

Is it distorted/fuzzy sounding? Any electrical noise in the audio (spark plug popping/alternator whine?).
It could actually be an over-voltage condition when you increase engine speed.
Have you tested your alternator output?
If the diodes are going bad(leaky diodes) in the rectifier section of it-AC current can find it's way into DC electronics such as radios and PCM computers. The alternator, besides generating electrical current-also acts like a radio transmitter. Unregulated or poorly regulated-the AC frequency and harmonic multiples of that frequency (high and low) can find it's way into all sorts of places it's not supposed to be.
Have a competent auto electrical shop check your alternator/rectifier diodes/regulator. It's relatively cheap and easy.
AC current can cause audio amp problems as the finals operate on AC themselves. Transformers, which all audio amps have are very susceptible to AC frequency harmonics.
Also an over-voltage condition-caused by a failing alternator voltage regulator can cause havoc by running amp primaries out-of-range. They are internally regulated, but only to a point. If the primary audio amp in the stereo is running at too high a voltage it will eventually damage it-but first it will overdrive the finals-causing garbled audio output.
Alternator output usually increases with RPM up to a point. The regulator on the alternator is there to keep it below damaging levels.(Yours may not be working like it should and the voltage limiting may be out of range(too high) when RPMs increase.)

You may have just accidentally invented a voltage-regulator-troubleshooter

BTW-I have a near-mint condition '87 Caravan with the Mitsubishi 2.6L four cylinder from heck in it
One timing chain/guides and three hundred valve adjustments later-she's still noisy and goes like a turtle on crack-but she just won't die
Gotta love 'em..

[nickbuol]

OK. For the "garble" it is like if a person was to gargle water. That is the best I can explain it. Not staticy or fuzzy sounding. I will see about getting the alternator tested and go from there. Thank you so much...

Any other last thoughts of what else I could try?

[Three_Fingers]

Hope I was of help.
Sounds like an RF problem-like an overdriven amp, or 'heterodyne' condition, where an unwanted harmonic bleeds into the wanted signal frequency to create a multiple that sounds like crap. Because it changes with RPM, I'm assuming the alternator has something to do with it.

Similar to CB adjacent-channel 'bleed-over'.
The only RF generators on any car are electric motors, spark plugs and the alternator.
Hmm...
Just for the helluvit-what ya got the radio grounded to?
Did you use a metal ground strap from the radio to the body?
Ya'd be surprised at the noise rejection ya can accomplish when your receiver/amp's case is properly chassis-grounded. The case acts like a shield then, keeping unwanted RF noise out.

As a last resort-you could always try using another power lead (connect to a different point for +12v).
Some power leads are just closer to the noise than others.

[nickbuol]

There is a nice, thick braided metal "strap" that attaches to the metal casing of the radio. I guess I have no idea if the other end is secure, but I don't know why it wouldn't be....