SE Heated Seats In Non-SE Mx-3 + Mod (Pics)

[stratman1988]

Anyone who has tried to reassemble one of these heated seat switches will quickly realize that gravity is not their friend. To help put the switch back together I find using a small amount of cotton ripped off the end of a Q-Tip shoved into the notch of the lever will widen it enough that it sits tightly on the main board allowing you to turn it upside down and lock it in on top of the spring loaded ball bearing without too much problem. If the switch doesn't have a positive snap to it you've messed up and need to take it apart and try again.

[Nd4SpdSe]

Instead of using resistors on the ground wires to bring the voltage down for the LEDs, a more clever way is to use a voltage regulators. They're chips that maintain a certain voltage and filter the excess to ground, so you don't have to worry about the intrinsic resistance of the LED when trying to bring the voltage down with a resistor
They're are also small enough that they can be soldered in on the board inside the switch making it a seamless conversion. You'll also need a little scrap wire to patch the ground of each voltage regulator to the ground wire.

The voltage regulator may be more cleaver, but it's more complicated and I honestly don't see that fitting side the switches at all. I had to do some triming just for the led leads, no way a regulator would fit inside if I couldn't get the resistors cleanly inside. Besides, you'd need 2 of them since each LED is on a different circuit. There's nothing wrong with the resistors, they're cleanly mounted inline to the ground and you wouldn't of known that they were there if I would of used non-clear heat shrink.

I've got them back in the car now and they look great but the logo light never really comes on even when the lights are turned on.
I know the light works cause I tested the circuit, I wonder if the logo light was ever meant to come on the in special edition or if it's just there for appearance?

As you can see, mine works just fine and that is how it's designed to work.


Sometimes over-engineering something causes more headaches than it's worth. You may not like the resistors, but it's so simple there's no reason for it not to work unless the wiring is wrong.

[stratman1988]

The voltage regulator may be more cleaver, but it's more complicated and I honestly don't see that fitting side the switches at all. I had to do some triming just for the led leads, no way a regulator would fit inside if I couldn't get the resistors cleanly inside. Besides, you'd need 2 of them since each LED is on a different circuit. There's nothing wrong with the resistors, they're cleanly mounted inline to the ground and you wouldn't of known that they were there if I would of used non-clear heat shrink.

You're right, it is a more complicated way to achieve the same result. The reason I opted to use a voltage regulator instead of a resistor is because the internal resistance of the LED changes with temperature and can be difficult to determine. A voltage regulator ensures the LED get a clean supply of the correct voltage.
The components do fit on the board, here a quick photo I took:

It's tight but feasible

Also I tested the wiring harness in my MX-3 SE, and I was wrong, the logo light should come on when the lights are turned on. I retested the blue LED on my switches and found that the voltage regulator wasn't working. I measured a much higher current coming out the logo light side than the switch side on the wiring harness in the car, so I'm thinking the regulator I speced for the blue LED couldn't take the current and fried. I tested in in the car and it got very hot to the touch. The red LED regualtor can handle 1A while the blue can only take ~200mA so I think using a hardier regulator should be the answer.

[stratman1988]

Is my method over-engineered? I confess yes a bit, I wanted the LED's to work as if the car had rolled off the line with LEDs in the switch. I bet if those switches had originally been made with LEDs you would see two voltage regulators printed on the circuit board.

[Nd4SpdSe]

You're right, it is a more complicated way to achieve the same result. The reason I opted to use a voltage regulator instead of a resistor is because the internal resistance of the LED changes with temperature and can be difficult to determine. A voltage regulator ensures the LED get a clean supply of the correct voltage.
The components do fit on the board, here a quick photo I took:
http://a.imageshack.us/img163/4414/seatswitch.jpg
It's tight but feasible

Also I tested the wiring harness in my MX-3 SE, and I was wrong, the logo light should come on when the lights are turned on. I retested the blue LED on my switches and found that the voltage regulator wasn't working. I measured a much higher current coming out the logo light side than the switch side on the wiring harness in the car, so I'm thinking the regulator I speced for the blue LED couldn't take the current and fried. I tested in in the car and it got very hot to the touch. The red LED regualtor can handle 1A while the blue can only take ~200mA so I think using a hardier regulator should be the answer.

Indeed you are right, you got them in there, but I totally disagree that a factory vehicle would of regulators in them and if anything, would use resistors as well, or just plain 12v LED's. I've used them in the past but RadioShack doesn't like to keep them in stock and the only ones they have in regular stock at The Source now are in a solder with an in-line resistor anyway.

As you can see with yours, you're doing some extra troubleshooting to figure outhe right regulator, but it's easy to calculate exactly what you ned when you have all the values of the LED itself and the supply voltage. Or even easier, if you want to cheat like I do, use this:
http://linear1.org/ckts/led.php" onclick="window.open(this.href);return false;

All the LED's I buy have the specs in the packaging. Yes, LED resistance may change with the temperature, but so does everything else. And we're also talking about an LED, it's able to handle a good variance in voltage...this isn't sensitive electronics here. I'd be almost willing to put money on it that you couldn't or barely visually see the differenece in the LED brightness between summer and winter.

[stratman1988]

Ahhh a calculator changes things!

[stratman1988]

I've edited my old post and using the calculator I respeced out the LEDs to be paired with resistors. I've also changed out the red LED for a brighter one that will be closer to the brightness of the blue LED. If you're happy with the changes Nd4SpdSe I recommend replacing the old radioshack parts with the new Digikey ones in the original how to post.

[-eunos-]

ohhhhhhhhhhhhhhh..... so thats what the spare blanking plates are for either side of my handbrake..! the switches for the heated seats!, not to mention the big white plugs under the seats...

ha ha... mybad...

Australia is too hot to warrent those... lol

[Nd4SpdSe]

I've edited my old post and using the calculator I respeced out the LEDs to be paired with resistors. I've also changed out the red LED for a brighter one that will be closer to the brightness of the blue LED. If you're happy with the changes Nd4SpdSe I recommend replacing the old radioshack parts with the new Digikey ones in the original how to post.

Excellent. Ya, it wouldn't be a bad idea, i'll add those later actually, but I'm personally more of a brick-and-mortar store person. I hate waiting for shipping and you can't guarantee any service or help, or even someone just to bounce ideas over. Mind you, The Source isn't much good for that, but I've also got a local electronics place called NuTech and that's all they deal with. And I hate ordering from the US, I avoid it at much as possible, and I like looking at the parts before I buy. Like those regulators, although the size is lited, I can picture it much better if I see the part first, I can be picky on size, style or even feel.

ohhhhhhhhhhhhhhh..... so thats what the spare blanking plates are for either side of my handbrake..! the switches for the heated seats!, not to mention the big white plugs under the seats...

ha ha... mybad...

Australia is too hot to warrent those... lol

Quite, but the USA didn't have them either, but their Mx-3's had the center section around the handbrake without the blanks....don't see why they didn't do that in Australia, unless they do..

[MrMazda92]

Quite, but the USA didn't have them either, but their Mx-3's had the center section around the handbrake without the blanks....don't see why they didn't do that in Australia, unless they do..

I haven't peaked in this thread for a long time, but I happened to tonight after resetting my cookies(lol, it was "unread" again), and I need to correct this.

The deep consoles(94+) in the U.S. did have the blanks, although both my '92 and '93 MX-3s did not have them originally.