A/C Compressor Zener Diode to stop radio popping

[Brett Dikeman]

On Thu, May 7, 2009 at 12:52 PM, Henry A Harper III <hah at alumni.rice.edu> wrote:

>> Thanks Kneale.  Do you, or does anyone reading, know whether this is
>> only required/helpful with the factory sound system or is there/would
>> there be popping with aftermarket components as well?
>
> I don't think I have ever heard any popping from the a/c compressor on the
> 12 year old aftermarket system in my car (Kenwood CD head + outboard amps).
> So I vote for Bose-only issue.

It's not a "bose-only" issue, and not all cars are affected, because
in some, they already have the diode.  On the 200q20v there was a
recall to REPLACE (or install?  I forget which now) the diode.  It's
called inductive kickback:

http://www.opamp-electronics.com/tutorials/inductor_commutating_circuits_3_03_08.htm

...and the cause is the A/C compressor clutch's electromagnet.  The
pop noise is from a large voltage spike.  If you feel comfy plugging
your GPS/iPod/etc into the cig lighter with those spikes, be my guest
:)  It's a cheap fix...

Brett