A/C Compressor Zener Diode to stop radio popping

Kenneth Keith auditude at gmail.com
Sat May 9 14:59:03 PDT 2009

Hi Steve,

How've you been?  Thanks for the informative post.  It's not late for
me as I parked the 200q20v when the alternator belt jumped off.  I'm
working on mail ordering a new one along with some other parts to
amortize shipping.  I don't think most of the locally available belts
fit as well as a Contitech or Gates, I heard.  I had the "alt belt
jumping ship" thing happen before, usually when driving somewhat
spiritedly.  It seems to happen when shifting at high rpms.

I found that SA15A part number on Mouser.com, which is cool because I
need to get a couple of other parts from them (a ceramic resonator to
fix an old Nakamichi home remote control and a digital voltmeter for
my VFR800).  But the suppressor isn't in stock and has a 9 week
leadtime from them.  I'm not sure if it's worth ordering from there,
but that ceramic resonator is hard to find so I may just place the
order.  I don't know a whole lot about electronics, in particular what
a resonator does, but I can tell when a lead is broken off flush on a
board component that came loose inside the broken remote. =)

I found that suppressor part number here as well, for $0.15 each.

There's a local electronic component store that I'll check before I
resort to ordering online.  I don't make it to junkyards too often



"urq" <urq at pacbell.net>
> .... sorry it took a while to get to this Ken,
> I would recommend that you look into the "SA15A" transient suppressor,
> manufactured by several sources ... Littelfuse, Fairchild ...
> I did a quick web search ... many places (like DigiKey) have an outrageous
> minimum quantity ... far too many for even a group buy.  I did find a
> retailer who would sell them individually for $0.69 and seem to be offering
> a no minimum order sale ...
>        http://store.americanmicrosemiconductor.com/sa15a.html
> I have never done business with this company, so I can't vouch for them ...
> you may want to call them rather than placing an on line order.  They do
> indicate they've been around a while, and they have an office in the USA.
> I may look into doing this mod on the V8s ... assuming they are prior to the
> VIN break Scott mentioned.  If I do this I'll document it for others.  For
> those DIYing this be aware that the device is directional
> You may want to look for one of the factory parts in a car in a wrecking
> yard ... I doubt it would be something a person would specifically seek.
> Your follow on question asked if the mod will work for other non-factory
> stereos ... if you are hearing a pop when the compressor is switched the
> answer would be yes, it will likely help you too.  Some stereos may do a
> better job of filtering power transients.  The compressor clutch is the
> source of the noise, it is a large inductive source, so when power is
> applied and removed a transient is generated.
> HTH and IUD!
> Steve Buchholz
> -----Original Message-----
> Does anyone know where I can find the appropriate Zener Diode to use
> with the a/c compressor (patient is a 200q20v) to stop the feedback
> popping when the clutch cycles?  I found some on Mouser.com but they
> are sold by large quantities and I just need one.
> http://www.sjmautotechnik.com says it needs to be one with an 18v
> breakdown voltage.
> Has anyone done the mod?  It's described here:
> http://www.sjmautotechnik.com/trouble_shooting/elec.html#click
> Cheers,
> Kenneth

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