This is an informational page to show how a rectangular universal automotive heated switch is wired. This applies to the very popular Dorman 901-899, which is used in many vehicles including Infiniti G20 2002-99, Infiniti I30 2001-96, Infiniti I35 2004-02, Infinity QX4 2003-97, Nissan Maxima 2003-95, Nissan Pathfinder 2004-93 and many others, including some Subaru and many universal applications that can be purchased online from Amazon and eBay.

Here is what the front of the universal switch looks like. The Dorman version has an arrow pointing towards the drivers side.

Here is the rear of the switch. The Dorman part is blue and has a vertical line at the top. The universal one is black in the rear and has the same shape plug without the vertical bar at the top.

The pin-out looks like this. The top left terminal is battery negative, for the LED indicator. The bottom left is the positive 12 volt output to the up position or high heat setting for most systems, which bypasses the relay and powers each heating pad with +12vdc. The top right terminal is the positive 12 volt output when the switch is all the way down in the low setting, which is usually wired to close a relay which powers each pad in a series, which in effect powers the seat pads at half the voltage. The bottom right terminal is positive +12vdc input from a ignition switched, fused battery source. This provides power to the switch and seat heaters.

This is a sample wiring diagram, which is how most universal and some factory seat heaters are wired. It takes a minute to understand what is happening, but essentially when on high it powers each seat pad with 12 volts and ground, in effect running the heating pads in parallel. When you switch to low, it reroutes the negative through the relay, thus putting the heat pads in series, which cuts the voltage to 6 volts to each pad, which is why it runs cooler.

You can buy the genuine Dorman part here https://amzn.to/44QF8m7

You can buy the universal version much cheaper here https://amzn.to/4pj0TCr

If you need the universal round version, you can get them here https://amzn.to/4spRcoK

For a full (2) seat universal kit, I recommend the Rostra 250-1870. These are carbon fiber seat heaters and are built better than some of the cheaper alternatives. This kit comes with the round seat heater switches. You can buy it here https://ebay.us/elSnuu

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