Polarity Reversing Switch

I'm hooking up some climate controlled seats in my vehicle and need some assistance with the wiring. They use a TED (thermo electric device) that when power applied one way is heat and reversed is cooled. And has a separate fan blower that requires one way power. My question is how do I wire up a rocker switch (3 position) to power relays or two separate push button switches (heat/cool) to activate relays to apply power to the TED and reverse it when another switch is pressed. I've attachedba basic picture of what I'm working with. Thank you in advance for your help.

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You can do it with a DPDT (on-off-on) switch plus a 12V relay as shown. This will require 4 wires to run to the seat.

or you can replace the relay with a bridge rectifier connected across the TE module to power the fan. That would only require 2 wires to run to each seat.

Thank you very much for your help and providing me with the drawing! But forgive my ignorance, as I do not quite understand the drawing and what the figures mean.

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The following is assuming that the fan is supposed to turn with both heating and cooling.

This will take 3 relays, a single pole double throw on=off-on toggle switch and 2 diodes.

The 2 relays for the heaters wired as follows. Relay 1 Ground terminal 87a and 85. Positive voltage to terminal 87. 86 to the outside terminal of the switch. 30 to one of the legs of the heater/cooler.

Relay 2 Ground to 87a and 85. positive voltage to 87. 86 to the other outside terminal of the switch. 30 to the other leg of the heater/cooler.

Apply positive voltage to the center terminal of the switch. On the outside terminals of the switch you also need to attach the non banded end of a diode to each. Connect the 2 banded ends of those diodes together. Connect that junction to terminal 86 of the 3rd relay.

Remaining wiring for the 3rd relay. Ground to 85. Positive voltage to 30. Fan's positive wire to 87. Ground the ground connection of the fan.

Does this method apply power in one switch direction and when the switch is positioned the other direction does it reverse the polarity to the TED but not the fan?

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EGURU, does your diagram turn the fan on in both switch positions and off while in the center? Also, what is KI? And what is the NO "gate" above the fan? Thanks again man

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Hi Yacob,

Sorry that this drawing is not clear - I am using the conventions used in electrical schematics versus the confusing (to me) semi-pictorial way that this forum uses to depict relays, etc.

Yes, my circuit does turn on the fan in both positions and off while in the center.

K1 is the relay coil (terminals 85 & 86 in the terms this forum uses).
"NO" is the relay's normally open contact (terminals 30 and 87 in the forum terms of reference).

You can replace the relay with a full-wave bridge rectifier (like a KBPC2504 which costs less than $3).

Mine heats in one position, off in the center and cools in the other position. Fan turns in either position other than off.

Thank you guys very much! I'm gonna give both a shot this weekend!

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yacob454 wrote:

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Thank you guys very much! I'm gonna give both a shot this weekend!

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Why bother with the 1 switch, 3 relay, and 2 diode solution when you can do it with a single switch and a $3 rectifier?

I agree. If your solution works (not doubting that is will), it will be the permanent solution

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An even simpler solution is a 3 position (ON-OFF-ON) 3pole double throw (3PDT) switch if you can find one locally (or on eBay).
You just use the third set of contacts to apply power to the fan (outer terminals to +12V and center to fan+).

Do we know what kind of current this device draws? Why would he need a rectifier?

Typically they draw 5A cooling and 10A in heating mode.
The fan won't run (or it will be destroyed) if the polarity is reversed.
A rectifier will provide the correct polarity regardless of the TEM polarity.

They do draw low amps.

EGURU, is the rectifier required if I use your DPDT switch and relay setup to run the fan the proper polarity in both switch positions?

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Apply power to both of the outside terminals of that pole of the switch. Connect the fan to the center connection of that pole. Fan will turn on with the switch in either position.

yacob454 wrote:

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They do draw low amps.

EGURU, is the rectifier required if I use your DPDT switch and relay setup to run the fan the proper polarity in both switch positions?

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If you use the DPDT switch with the relay, you do not need the rectifier.

Awesome. I asked because I already had those two parts

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I used your single dpdt switch and relay combo and it worked like a champ!! Thanks again for everyone's help!

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yacob454 wrote:

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I used your single dpdt switch and relay combo and it worked like a champ!! Thanks again for everyone's help!

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Glad I could help.

btw - What brand/model of seat heater/cooler did you install?
Did you find it hard to install?

They are from a 2012 Ford truck. Incredibly easy actually, just took time with so many wires.

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