Brainmooore - Heated REAR electric seats...?

[M16]

Just got hold of some heated front leather sport seats for my Touring and am currently having my rears re-trimmed to match.

An electrical techy question tho:

I have the option of fitting heated rear elements to the rears, but want to use OEM switches (maybe mounted in the doorcard nect to the window switches?).

Can I run off the the loom for the front seats? Would that overload the thing?

Or if I was to use the system from the new supplier, could I wire their loom into OEM switches so it still looks factory?

Would love some help on this.

Pix on the way!

[dazleeds]

i think you have just missed brian by minutes

he has gone away for 3 weeks as of this morning

but im sure someone else will be able to answer the question for you



i dont really have an answer for you but would imagine the rears would need there own looms rather than running thru the front looms

it may be possible but youd probably need to do some upgrading so as not to overload the circuits etc

sorry cant be more help

Daz

[M16]

BALLS!

I'm sure there are other bright sparks that could help.

I think I'll have the elemnts fitted anyway and the I can figure out the wiring another day.

The safest / best approach might be to use the 3rd party wirirng and find a way to mate their loom to the OEM switches. It can't be that difficult as it's not the most complicated system in the world.

[slinky2000]

I'm sure you could wire it upto the switch, surly all the switch does is cut or supply power. Evening running off the front seat loom I wouldnt see a problem,

I'm no expert though

[M16]

Need an expert

I can see problems doing that.

I'm not sure what thye relay / fuse and wiring was designed to power.

Also, I want the rears to have their own switches.

Then there's also the 2 levels of heat.

Conventional wisdom would be to just 'extend' front loom to the feed the rear with 2 more swithes off that but that brings up the overload issue.

Need to get all the tech figures and have a spark go over them I guess and tell me if I'd start a fire doing that...

[Speedtouch]

Mug up on Ohms Law and work out how much power/current the rears will need and whether the fuses and wiring of the front ones is up to the job.

Power (W) = Current (Amps) X Volts

Current (A) = Power (W) / Volts (V)

etc.

[M16]

Need to know what the rear elements draw first tho.

Then I also need to know what the hell you're on about.



I kind of get what you're saying but need to translate that into hardware needs.

[Speedtouch]

You could try connecting them to a fully charged car battery separately out of the car and measuring the current consumption to get an idea.

[M16]

True.

Then I need to find out the max load for front loom/relay/fuse and see if it will cover it?

Right?

[Speedtouch]

Yes. Maybe a BMW dealer might be able to advise also?

[M16]

They won't want anything to do with non-factory stuff.

Though I don't know where you'd get the info from if not them...

[Speedtouch]

Best just to measure the current consumption then ensure your cabling and fuses are up to powering it: you may well need an extra relay triggered from the front seats to transfer power via another loom running to the rears.

[nickso]

wouldnt you be easier to get a front seat loom and run it back to the rear seats. depending on where your switches were mounted it might just reach. then you could adapt the plugs at the acc socket to accept both looms. the only thing you would need to calculate then is your new fuse rating and possibly upgrade the wiring from the fuse to the acc socket.

please feel free to tell me if im talking bollocks as this a just a guess from someone who has stripped out a heated loom.

[M16]

That does make sense.

I'd have to split the accessoy panel feed to power 2 looms and then perhaps uprate the fuse as you said.

Wouldn't it confuse the relay? If I switch the left rear seat on, wouldn't that also heat up fornt left to etc?

I can't believe Brianmoooore has gone for 3 weeks!

Maybe he's got a BlackBerry...

[munky30]

E30's all over the uk will be falling apart at the seams now brians gone...

[Danhbmw]

The safest / best approach might be to use the 3rd party wirirng and find a way to mate their loom to the OEM switches. It can't be that difficult as it's not the most complicated system in the world.

If I were doing it to mine this is how i'd do, I'm assuming the 3rd party loom comes with the 3rd party elements, if this is the case then you know 100% that loom is safe to use with those elements (ie correct load ratings) then just as you said figure your switches out!

[M16]

Probably the best thing to do.

I'll ask them where they wire their looms into and ask to see the switches. It's 4 pins on the E30 one's...

[nickso]

Wouldn't it confuse the relay? If I switch the left rear seat on, wouldn't that also heat up fornt left to etc?

sorry i dont understand that bit. this is where my knowledge of the wiring in question may let me down.

if you had 4 switches powered by two looms and left one switch on then surely it would only be heating the seat in question? its no different to leaving one switch on on a standard setup.

you could use a 3rd party loom etc but it seems awfully time consuming considering you could easily have a ready made loom with switches. this of course depends on the original loom reaching the back seats

[murran]

why heat the rear seats? you dont sit in the back, do you?

[Karan]

no one can fit in the back.... how come u need heated seats??? good for kiddies in winter i guess (andyboy and pacer interested?)