[V8] Seat Heater switches

[Dave Saad]

This would be a big job. Not impossible but you need all the stuff from the Audi - switch, control unit, and the Mazda heater would have to be wired similar and have a similar resistance to the Audi. That is a lot to go through when all you want is a variable current supply. Actually (thinking out loud here...) the simplest circuit would be a variable duty cycle solid state switch (relay).
I don't think that would be hard to build and you get exactly what you want.
Read up on the LM555 timer chip. There are thousands of examples of this circuit on the web.
Your basic parts list is the 555, a few resistors and capacitors, a driver transistor, and a box to put it all in.

Dave
Sent from my iPhone

> On Jan 31, 2015, at 8:27 AM, Nicholas Miller <chance9121 at gmail.com> wrote:
> 
> I think I've seen this in the diagrams.  It states "relay" but it looks
> like a transistor.  This is the item you refer to?  I could get ahold of
> those and replicate it in my car.  The trick is then if the installed
> heater will play nice.  Is it literally a heat sensor that communicates
> back to this relay, or does it just know to vary the current/voltage?
> 
> Either way, understand it may be an all or nothing package.  I don't care
> for my 1-setting Mazda 3 heaters... They are a bit all or nothing.
> 
>> On Sat, Jan 31, 2015 at 6:18 PM, Huw Powell <audi at humanspeakers.com> wrote:
>> 
>> Hi Nick,
>> 
>> In short, what you want to do won't work.
>> 
>> The Audi seat heater switches with multiple heat settings (at least, thes
>> that I am familiar with) depend on a sensor in the seat to measure the heat
>> level.  There is no potentiometer, per se, to simply adjust the current
>> delivered.
>> 
>> You'd need to install the sensor and the control "relay" for each side as
>> well as the switch.
>> 
>> I suspect the control units compare the resistance of the sensor with the
>> resistance set at the switch to turn the heat on and off at the desired
>> temperature.
>> 
>> All the best,
>> 
>> Huw
>> 
>> 
>>> On 1/31/2015 4:51 AM, Nicholas Miller wrote:
>>> 
>>> Hey everyone,
>>> 
>>> Does anyone have some pairs of Heated seat switches around?  I want to
>>> retrofit a few of my cars with these Audi/vw switches, as I have a 1
>>> position button on my heaters for right now.  I'd like to try and retrofit
>>> the Audi switch into the car.
>>> 
>>> Has anyone done this before?  I'm not sure if it will work, but in my head
>>> it should be simple, I'm assuming its Vin, Gnd, Vout, and Backlight Vin,
>>> and the switch operates like a potentiometer.
>>> 
>>> P.s.  The candidates are 2 MX-5s, a Mazda 3, and a Mitsubishi Eclipse.
>>> Cause its cold up here in MN.
>>> 
>>> Cheers all,
>>> Nick
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