Britpart heated seat heaters

[L19MUD]

As part of my Defender build I have fitted this kit into my newly refurbished seats. The switch that came with the kit controls both the left and the right seats and both stages of the heating (warm and hot). The switch goes to a control block which I presume has a couple of relays in it. This switch does not fit with the rest of my dash so I want to change from one switch that came with the kit to two carling switches, one covering each side. I would presume an Off-on-on switch should be able to do this.

There are 8 wires going to the original switch. Has anyone else got this kit and rewired to different switches before I reinvent the wheel? Can't be that difficult?

https://www.britpart.com/all-parts/da5717

 

I asked Britpart for a wiring diagram but they won't supply it incase I create a fire hazard!

 

[western]

Looks like a sideways motion rocker switch as it allows both front seats independent use, quote from the link, 

Quote

The switch allows the driver and passenger to select their own heat setting. 

 

[L19MUD]

26 minutes ago, western said:

Looks like a sideways motion rocker switch as it allows both front seats independent use, quote from the link, 

 

Yes I think you could be right, question is how does it also deal with two stages of heating? It appears to be a 'mom' switch though so that could be covered by the control module

[L19MUD]

[western]

if its not a rocker, then a push on for 1 setting & push again for 2 setting but not sure how it would switch 1 or 2 seats on/off independently.

[Jon White]

Yes I have that kit with that switch. The two sides operate independently. Its more than just a switch however as there are bicolour leds in there, plus illumination. Each switch is a momentary, so multiple pushes cycle through off/high/low

Edited April 14, 2020 by Jon White

[L19MUD]

That switch can't be unique to Britpart, I wonder if I can find it elsewhere. I don't really want to pull it apart as it may be my only option if I can't work out a way round it

[L19MUD]

Ok i looked further into this last night by connecting it up to some power and pulling the cover off the module and the switch. The switch rocker operates each side independantly as said. I press and the LED goes red, two it goes to Orange and three back off, same for each side.The 8 pins that go to the switch are as follows (measure off the circuit board where the wires are soldered.

 

1 - 5v output to switch (assume left or right feed)

2 - Ground

3 - 12v output to switch illumination

4 - 5 v output to switch (assume left or right feed)

5 - 1.9v return from switch RHS Orange LED only

6 - 1.9v return from switch RHS Red LED only

7 - 1.9v return from switch LHS Orange LED only

8 - 1.9v return from switch LHS Red LED only

 

1-4 are no problem if using a normal switch and 5-8 would be fine if the voltage had not dropped. How would the circuit in the switch be acheiving this?

 

Pictures of control module and switch interior

 

[geoffbeaumont]

From what you describe each side connects a separate return feed individually for the two power levels (i.e. only one of the high and lower power returns are connected at a time - not both together)? In that case how about a two way rocker switch for each seat? Centre off, up for high power, down for low, something like that?

Would also mean you could position the switches in different places to be convenient for the occupant of the seat each controls.

[L19MUD]

15 minutes ago, geoffbeaumont said:

From what you describe each side connects a separate return feed individually for the two power levels (i.e. only one of the high and lower power returns are connected at a time - not both together)? In that case how about a two way rocker switch for each seat? Centre off, up for high power, down for low, something like that?

Would also mean you could position the switches in different places to be convenient for the occupant of the seat each controls.

Hi Geoff, that is exactly what I would like to do and you are correct the return feed is individual. My only concern is that the switch feed is 5v from the control box (obviously connected to a 12v battery for test purposes) but the return feed from the switch is 1.9v

If I just used a normal on-off-on switch the return feed would also be 5v and I don't know what the consequences of that would be? Seems odd the return feed is a lower voltage?

 

[Snagger]

My kit was bought about 15 years ago, so had no electronics, but it did have very small switches and a relay.  I didn’t want to use those either, but I think the relay was purely to stop battery drain with the engine off,  so was probably to be triggered by the ignition switch and give a feed from the battery to the switches.  Seat heating uses very little power, maybe a few amps at most, so running them directly from the Carling Tech switches has caused me no problems at all.  You just need to run a fused feed to the switches, an output from the switch to the pads, and then earth the pads (I used a ring terminal to one of the seat rail bolts, with cleaned up surfaces and a dollop of grease to prevent the contacts corroding, but you can run a longer earth lead wherever suits you).

[geoffbeaumont]

3 hours ago, L19MUD said:

Hi Geoff, that is exactly what I would like to do and you are correct the return feed is individual. My only concern is that the switch feed is 5v from the control box (obviously connected to a 12v battery for test purposes) but the return feed from the switch is 1.9v

If I just used a normal on-off-on switch the return feed would also be 5v and I don't know what the consequences of that would be? Seems odd the return feed is a lower voltage?

It seems unlikely to be anything other than resistance. Possibly the indicator lamps, though it seems a large drop for just them?

If you're worried it'll burn something out just add a suitable resistor in series with the switch.

[L19MUD]

I think it's worth the risk to be honest. If the smoke comes out I can rewire as snagger suggests

[Snagger]

5v is a common electronics voltage.  My bet is the electronics are there to allow a single press button to control a cycle of different modes, probably both off, left on, right on, both on and then back to both off, just like cycling through the flashing sequences on some Christmas tree lights.  You don’t need any of that.  The heat pads are resistive (that’s how they generate the heat), so they don’t have any voltage control, just on or off, so a switch, wiring run and fuse are all you need.  You could be fancy and use a rheostat or potentiometer switch to have variable temperature, if you want.

[L19MUD]

5 minutes ago, Snagger said:

5v is a common electronics voltage.  My bet is the electronics are there to allow a single press button to control a cycle of different modes, probably both off, left on, right on, both on and then back to both off, just like cycling through the flashing sequences on some Christmas tree lights.  You don’t need any of that.  The heat pads are resistive (that’s how they generate the heat), so they don’t have any voltage control, just on or off, so a switch, wiring run and fuse are all you need.  You could be fancy and use a rheostat or potentiometer switch to have variable temperature, if you want.

Yes I agree. I am going to wire into the existing control box for now with a new switch each side as that gives me a pre set hot and warm temperature for each seat without messing about trying to do that myself

[Snagger]

I suspect the Carling switches won’t work with that electronic unit as it is likely to be a momentary switch that sends a pulse, not a continuous signal, and the one switch appears to do both seats.  That’s just a guess without seeing the unit.

[geoffbeaumont]

1 hour ago, Snagger said:

I suspect the Carling switches won’t work with that electronic unit as it is likely to be a momentary switch that sends a pulse, not a continuous signal, and the one switch appears to do both seats.  That’s just a guess without seeing the unit.

The switch doesn't appear to behave that way from @L19MUD's description above. There are separate signal wires from the switch, and it contains indicator lights that need to maintain state. I didn't read it as the voltage was only present when the switch was being pressed - if I'm wrong about that then forget the rocker switches, it'll need momentary ones.

[L19MUD]

3 minutes ago, geoffbeaumont said:

The switch doesn't appear to behave that way from @L19MUD's description above. There are separate signal wires from the switch, and it contains indicator lights that need to maintain state. I didn't read it as the voltage was only present when the switch was being pressed - if I'm wrong about that then forget the rocker switches, it'll need momentary ones.

It's not a mom switch, it latches into position so the voltage output is constant 

[Snagger]

OK.  I thought the extra wires were for the indicator LEDs rather than separate switch outputs.  I don’t see the need for an ECU with mechanical switches with latched contacts.  I can’t see how that switch would control each seat independently if it wasn’t a momentary switch that cycles the ECU through the permutations as mentioned, but I’m only looking at a photo.  Still seems fiddly, unnecessarily complex and if it is a cycling switch, awkward to use if you are happy to fit two separate dumb switches instead.

[Gazzar]

I am a bit leary of electronics supplied by a known low cost supplier.

Would two simple independent switches be an option?

[Snagger]

The Britpart kit isn’t made by them, or even to a spec they made - it’s just an off-the-shelf kit made for people who don’t want to wreck their dash board with drilling lots of holes for several big switches.  That’s fair enough for a Ford or Nissan, but not really appropriate to a Land Rover.  But the pads will probably be fine, and that’s the bit you can’t make at home!