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Heated Seat Switch Pinout and PCB


j_jza80

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Problem solved. full guide to fitting heated seats here: http://www.mkivsupra.net/vbb/showthread.php?330119-How-to-Guide-Install-heated-seats-using-the-OEM-heated-seat-switch&p=4108429#post4108429

 

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I'm trying to get to the bottom of why my heated seat switch won't work, which is becoming pretty infuriating! :D When I tried a new switch the other day, the dash illumination fuse blew straight away.

 

According to the little information I can find on this subject, the heated seat switch pinout is as follows:

 

1: ground

2: power to LH seat heater (when button pressed)

3: illumination negative

4: main power in

5: illumination power

6: power to RH seat heater (when button pressed)

 

(see thread: http://www.supraforums.com/forum/showthread.php?661737-Aftermarket-seat-heater-with-oem-switch )

 

However, wiring the switch like this deems to produce sporadic results. It has blown a couple of fuses, and junked a dash dimmer switch. And the illumination seems inconsistent. i've just tried a different switch which I tested with a makeshift rig, and it actually made one of the PCB connections pop!

 

So, I've stripped down the switch, and this is the layout of the circuit board:

 

TOP

image

image

 

BOTTOM

image

image

 

Please excuse the basic diagrams! :D

 

So, straight away to me, it looks like pins 2 & 4 are for the button illumination, not 3 & 5 as per the pinout on Supra forums. The LEDs at the top end of the board indicate when each seat circuit is activated, so they must each connect to the main power input pin, and each seat power output.

 

I would appreciate it if anyone with more knowledge of PCBs could have a look at this for me, and save me a lot of time and heartache! :D

 

Thanks.

Edited by j_jza80 (see edit history)
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can I ask, did it used to work before?

 

- - - Updated - - -

 

That's why I'm looking for a UK spec owner :) would be easy enough testing the outputs with a test light. :)

 

If you can find anything, that would be great. Did you use relays for each seat?

 

Yes, two relays.

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On your Switch:

 

1. POWER OUT (SEAT 1)

2. ILLUMINATION

3. POWER IN (SWITCHES)

4. ILLUMINATION

5. POWER OUT (SEAT 2)

6. LEDS (COMMON)

 

- 1,3,5 should be thicker wires IF it is a +12v switch - if they are the same size as the others it probably runs through relays (Neg Trigger)

- 2 OR 4 will be a WHITE/GREEN which is ILLUM Negative - the other will be +12V with lights on

- 6 is PROBABLY a negative, but only if pin 3 is a +12v IGN.

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Realistically, the heated seats in mine (which are LS400) only draw about 3-3.5A when on. So each could be run from a 15a feed or even a 20a feed to power BOTH relays. You don't need to use a relay on the Ignition circuit because it is only going to be switching relays therefore doesn't draw any significant current.

 

So you are retrofitting heated seats is that correct? Do you want a loom diagram done?

 

JV

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Realistically, the heated seats in mine (which are LS400) only draw about 3-3.5A when on. So each could be run from a 15a feed or even a 20a feed to power BOTH relays. You don't need to use a relay on the Ignition circuit because it is only going to be switching relays therefore doesn't draw any significant current.

 

So you are retrofitting heated seats is that correct? Do you want a loom diagram done?

 

JV

 

So run the ignition live into the main feed of the switch, then use the outputs to switch the relays both the seat feeds?. That makes sense. :)

 

Yes, I'm retrofitting it. :)

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Thanks :)

 

Is it necessary to run the feeds for the relays/seats from the switched ignition live though? Surely using relays means they can, and should come straight from the battery/fusebox?

 

And also, the illumination has to be earthed back through the illumination ground circuit, or the dash dimmer won't work. :)

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Illumination - Correct sorry yes it'll ground through any White/Green wire (dimmer circuit) - easiest is to take that feed from the light on the Cigar lighter.

 

Yes you can take the 15a fused feeds to pin 30 on both relays from B+ at the fusebox, it doesn't really matter - the purpose of the relay is to allow a low current circuit ie switch to turn on/off a higher current circuit regardless of where the higher power circuit comes from.

 

Hope this has been helpful and good luck!

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Illumination - Correct sorry yes it'll ground through any White/Green wire (dimmer circuit) - easiest is to take that feed from the light on the Cigar lighter.

 

Yes you can take the 15a fused feeds to pin 30 on both relays from B+ at the fusebox, it doesn't really matter - the purpose of the relay is to allow a low current circuit ie switch to turn on/off a higher current circuit regardless of where the higher power circuit comes from.

 

Hope this has been helpful and good luck!

 

It has been very helpful, thank you :)

 

I'll be working on the premise that the pinout is backwards, and changing the current single relay for the twin as discussed. :) I'll post up my results, and post up an amended diagram for future reference :)

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