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30th November 2019, 20:31 | #1 |
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R75 CDTi Auto Conn SE Mk1 Saloon Join Date: Feb 2010
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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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1st December 2019, 14:28 | #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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1st December 2019, 16:26 | #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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2nd December 2019, 08:15 | #4 |
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R75 CDTi Auto Conn SE Mk1 Saloon Join Date: Feb 2010
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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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3rd December 2019, 09:33 | #5 | |
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Quote:
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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11th December 2019, 04:48 | #6 |
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OK. I've taken the seats out and confirmed that 12v applied directly to the element circuits get the seats toasty warm.
I have located the heated seat grounding point at the bottom of the NS A pillar, and cleaned the crimped rings with a wire brush. At the switch end, black is earth, and the yellow shows +12v, (I guess that's the permanent (ignition) live feeding through the seat thermistors? When I measure resistance across the switch in operation, it shows 0.8 ohms between black and yellow. I have tried different switches, they all do the same. (oh, and I've even shorted the black to yellow, bypassing the switch........NOTHING!) I have applied a new earth for the switch, no change. There must be a common fault here, as both seats do not work, but I cannot fathom out why!
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2nd December 2019, 09:37 | #7 |
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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.
Last edited by raykay; 2nd December 2019 at 09:54.. |
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