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Old 30th November 2019, 22:31   #1
Falcon Flyer
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Default Earthing point for heated seats?

Hi all,

my heated seats have become intermittent, but work fine out of the car with 12v directly applied.....

After extensive fault finding, switch and fuse replacements etc, I suspect now that I have an earthing problem. As the 75 has a multitude of earthing points, and before I tear my car apart looking for them, can anybody please direct me to the most likely earth?

Thanks!
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Old 1st December 2019, 16:28   #2
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According to the Haynes manual earth point are at base of the A pillars. If you have a multi meter you can use the continuity setting to confirm that, but I'd assume that's where it will be.
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Old 1st December 2019, 18:26   #3
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Failing finding an existing earth point just make your own to a nearby part of the cars body.
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Old 2nd December 2019, 10:15   #4
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Earthing point found, sadly no corrosion as a 'smoking gun'. All cleaned up and re-torqued up, but still an intermittent power supply to the seat, (intermittent meaning 7-10 seconds). Anyone like to explain why the seats are switched with an earth rather and positive?
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Old 2nd December 2019, 11:37   #5
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Quote:
Originally Posted by Falcon Flyer View Post
As the 75 has a multitude of earthing points, and before I tear my car apart looking for them, can anybody please direct me to the most likely earth?
The earth cables from the switches are connected to pins 15 & 16 of the 20 pin header (sealed connector) at the bottom of the centre console, along with several other earth cables. It is a cable from that header that is connected to the earthing point at the base of the 'A' pillar.

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Old 3rd December 2019, 11:33   #6
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Quote:
Originally Posted by Falcon Flyer View Post
Anyone like to explain why the seats are switched with an earth rather and positive?
I don't know James but looking at the wiring diagram in RAVE the seat heaters have three switches in series. First the ignition switch supplies the +12v, then there's a thermostat inside the seat and the final circuit to earth takes place through the operational switch on the centre console.

When you say that the supply is intermittent, every 7 to 10 seconds, are you measuring this with the supply disconnected from the element or with the whole circuit in operation?

Simon
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