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Discussion Starter #1
Recently had new seat installed but now I cannot get my wife’s seat heater turned off. Is there an easy way to check and/or replace the switch without tearing the seat completely apart? My wife loves the heated seat but not at this time of the year in the desert – already over a hundred degrees. My jokes about her hot butt have not been amusing to her. I’ve disconnected heater for now but the first time we ride over the mountain and the temperature goes below 60 I’ll have to stop and reconnect the heater. Any help or suggestions you guys can share will be appreciated.
 

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Just put an ohm meter across the 2 pins on the seat side of the connector. note the reading, then turn the switch off. At this point the reading should be infinite. Also as you switch from high to low on the switch the ohm value should change. If you have an actual ohm value with the switch off, I would suspect the switch is bad.
 

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sorchilla said:
Recently had new seat installed but now I cannot get my wife’s seat heater turned off. Is there an easy way to check and/or replace the switch without tearing the seat completely apart? My wife loves the heated seat but not at this time of the year in the desert – already over a hundred degrees. My jokes about her hot butt have not been amusing to her. I’ve disconnected heater for now but the first time we ride over the mountain and the temperature goes below 60 I’ll have to stop and reconnect the heater. Any help or suggestions you guys can share will be appreciated.
The switch easily pops out with a little pressure on the 2 mounting tabs that hold it in place. Use a small flat blade screwdriver and pry gently.

If the switch is bad you'll need to find an aftermarket unit that will fit the hole - I've NEVER found one that fits - and of course they are not available from BMW. Unless you buy a new heated seat! ;)

We've tested literally hundereds of LT heated seats after rebuilding - and I've never seen a switch go bad yet - although it has happened.

(Your wife does know that the middle position on the rocker switch is OFF - right? :D )
 

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Discussion Starter #4
Morley said:
Just put an ohm meter across the 2 pins on the seat side of the connector. note the reading, then turn the switch off. At this point the reading should be infinite. Also as you switch from high to low on the switch the ohm value should change. If you have an actual ohm value with the switch off, I would suspect the switch is bad.
If your talking about the connector that goes to the seat - mine has 4 pins. Which pins are the correct ones to check?
 

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sorchilla said:
If your talking about the connector that goes to the seat - mine has 4 pins. Which pins are the correct ones to check?
Having not looked at the switch I would guess that one pair are for low heat and the other for high. Using the ohm meter, figure out which pins are ground (negative). From there you should be able to figure out which hot lead goes with which ground. With the switch off, check across each power and ground. Then turn the switch on low check them each again and again on high. If you don't get infinite reading when the switch is off, it is defective.
 

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The four pin connector to the rear seat has a ground (brown) and a power lead (green/brown) and two wires returning to the backrest heater (grey and black). In the image below the backrest is item E9395 and the passenger seat is item E9368. The Grey and black wires coming from pins 1 and 3 of the seat connector loop back to pins 2 and 3 for the backrest. As you can see, when the heat is on low the power supply (green/brown) is connected to the Grey wire and when it is on high the supply is connected to the black wire. You should be able to use an ohmmeter at the 4-pin connector to determine if the switch is bad. As others have said be sure she understands that the center position of the switch is OFF.

 

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Discussion Starter #8
Switch is OK

Thanks for the great help. I removed the switch and checked with an ohm meter. It's good. It looks as if my problem is the wiring is the seat may be shorted. I'm thinking I should take the rear seat back to Mayer's and have them tear it down to look for some crimped wires. Am I on the right track?
 

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sorchilla said:
I'm thinking I should take the rear seat back to Mayer's and have them tear it down to look for some crimped wires. Am I on the right track?
Yes! If they were in the seat for the "rebuild" they may have nicked a wire or shot a staple through it.
 

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Am I missing something here? If the switch is good and in the "Off" position, there is no power to the seat so there is no heat. A short 'after' the switch should not be the issue.
Correct??
 

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bblalock said:
Am I missing something here? If the switch is good and in the "Off" position, there is no power to the seat so there is no heat. A short 'after' the switch should not be the issue.
Correct??
You are correct. But a short between 'before' and 'after' the switch could be the cause. A staple in the seat cover that pierced the green/brown wire along with either the gray or black wires would cause the heater element to be on all of the time. The easiest solution would be to use an ohmmeter on the 4-pin connector to determine if that is the case. If the ohmmeter proved that there was a short then I would pull all of the staples proximate to the switch and connector wire to see if it resolved the problem. Since there is no power to the backrest an errant staple in that cover couldn't be the problem.

For clarification - since the heater elements are low resistance, a short to either the low or high heat lines from the power input would *appear* as a short to all three. With the seat unplugged and the switch off there should be an open circuit condition from the green/brown wire to *any* of the other three. With the switch on (either high or low) there would be very low resistance from the green/brown to *any* of the other three. If one was to find low resistance with the switch off, they could pay close attention to the different readings from the green/brown to the other three. The lowest resistance would be the wire with the staple through it.

One also couldn't rule out the possibility of a coincidental switch failure, but as Ron stated there haven't been any cases of that that I have heard.
 
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