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1995-2002 Range Rover P38A
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Discussion Starter #1
I posted on this on another thread concerning the HEVAC unit, but it’s more about the seat heaters.

I think that cars which didn’t leave the factory with the heated seat and screen option had the seat heating elements fitted, but did not have the screen heating element. That’s what my Australian 2000 Vogue has.

Why bother getting the seat heaters working? I’ll never buy another car without them. My Mercedes SL500 got me hooked on the idea. The radiant heat from the seat heaters is a necessity for my delicate constitution. And yes it gets cold and miserable here in Melbourne, at least for a month or three in winter, despite our recent 47 degree summer.

Look under the seat to see the two elements and plugs going to to the BECM. It’s all in the ETM. Each element measures under an Ohm. They’re in series so that’s about 6 Amps when they’re on and 72 Watts – about right.

Lots of talk here that they’re not warm enough. Strip the seats down when you’re repairing any breaks (mine had a break in both bases – easy to find and fix) and replace the factory 35 degree thermostat in the seat base with a 50 degree unit from Marty’s page or on eBay – item number 513055118293. Now they’re the total bomb – not hot enough to scorch but I would not want them any hotter. Perfect, but they take a few minutes to warm up.

Source a HEVAC unit with the heated seat buttons fitted. There are two types – one for the GEMS and one for the Bosch. Lots of info about this. You can interchange the two but either swap will require wiring modifications. If putting an earlier HEVAC into a later car you will need to do two mods: Firstly fit the jumper for the AC compressor instead of relay 3 as written up at Range Rover P38 Maintenance repair improvements and tips learned by experience by ownership. and secondly fit an 82 Ohm 3 Watt resistor across the relay coil terminals of both relay 6 and 7 in the fuse box OR just fit the standard relays in there. The HEVAC unit with the heated screen is looking for those relays for it to work. By fitting the resistors you’re tricking the HEVAC into thinking it’s seeing relays.

Remember the engine has to be running for it to work. Listen for the little click from the BECM when they switch on.

If fitting a later unit to an earlier car you must fit a relay 3 in line with the AC compressor, as fitted to later cars.

That’s how I got mine to work perfectly. Thanks to Richard and Marty and others.

Tom
 

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1995-2002 Range Rover P38A
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73 Posts
Can you provide a link to the ebay item for Marty's 50 degree unit? The item number you gave does not seem to be valid. Thanks for your time.
 

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1999 P38 HSE 4.6 THOR
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37 Posts
Try this one:
283716934187

I doubt it's the same ad, but I think it's the same kind of product.
 

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1995-2002 Range Rover P38A
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155 Posts
Discussion Starter #4
That's an Australian seller but the link is valid: 513055118293 | eBay

They seem to be widely available. I can't seem to find Marty's site today.

KSD301 is the part number - you want the 50 degree version. My seats are warm and toasty - you wouldn't want them any hotter. Best mod I ever did!
 

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Registered
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37 Posts
I posted on this on another thread concerning the HEVAC unit, but it’s more about the seat heaters.

I think that cars which didn’t leave the factory with the heated seat and screen option had the seat heating elements fitted, but did not have the screen heating element. That’s what my Australian 2000 Vogue has.

Why bother getting the seat heaters working? I’ll never buy another car without them. My Mercedes SL500 got me hooked on the idea. The radiant heat from the seat heaters is a necessity for my delicate constitution. And yes it gets cold and miserable here in Melbourne, at least for a month or three in winter, despite our recent 47 degree summer.

Look under the seat to see the two elements and plugs going to to the BECM. It’s all in the ETM. Each element measures under an Ohm. They’re in series so that’s about 6 Amps when they’re on and 72 Watts – about right.

Lots of talk here that they’re not warm enough. Strip the seats down when you’re repairing any breaks (mine had a break in both bases – easy to find and fix) and replace the factory 35 degree thermostat in the seat base with a 50 degree unit from Marty’s page or on eBay – item number 513055118293. Now they’re the total bomb – not hot enough to scorch but I would not want them any hotter. Perfect, but they take a few minutes to warm up.

Source a HEVAC unit with the heated seat buttons fitted. There are two types – one for the GEMS and one for the Bosch. Lots of info about this. You can interchange the two but either swap will require wiring modifications. If putting an earlier HEVAC into a later car you will need to do two mods: Firstly fit the jumper for the AC compressor instead of relay 3 as written up at Range Rover P38 Maintenance repair improvements and tips learned by experience by ownership. and secondly fit an 82 Ohm 3 Watt resistor across the relay coil terminals of both relay 6 and 7 in the fuse box OR just fit the standard relays in there. The HEVAC unit with the heated screen is looking for those relays for it to work. By fitting the resistors you’re tricking the HEVAC into thinking it’s seeing relays.

Remember the engine has to be running for it to work. Listen for the little click from the BECM when they switch on.

If fitting a later unit to an earlier car you must fit a relay 3 in line with the AC compressor, as fitted to later cars.

That’s how I got mine to work perfectly. Thanks to Richard and Marty and others.

Tom
Thanks for posting this. I love my seat heaters, but given their failure rate (and the absolute PITA to fix them once broken in the seat), I went with sheep-skin covers. Living just south of the artic circle in Michigan, they are the best investment I've made in my P38 to make it comfortable in the winter.
 

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1995-2002 Range Rover P38A
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155 Posts
Discussion Starter #7
Well it gets cold here too - but not Michigan-cold. I'm just soft, these days.

I think that if the seat heaters were used regularly since the car was new, it's much more likely that the elements would be cracked and broken, due to the repetitive heat and cool cycles.

Mine were broken in only one spot - the bit of element that goes horizontally across the seat base. Both seat backs were tip top.

Repairing them is easy when it's all apart, but my main motivation was to swap over the bases to equalise the wear on the bases.

Tom
 
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