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mwestcrew

Member Since: 09 Dec 2019
Location: South Warwickshire
Posts: 216

2011 Defender 130 Puma 2.4 HCPU Baltic Blue

https://www.12voltplanet.co.uk/adjustable-...v-10a.html

Here’s an example. This relay is triggered by a momentary connection to 12v positive. Wide variation if times available. This one is quite pricey but there are cheaper available. Push button switch would actuate it and turns itself off after specified time. Most modern cars have timers on the seat heaters 2011 130 Utility Body
2005 110 Van

13th Sep 2022 2:46pm

ScarboroughSeadog

Member Since: 21 Jul 2022
Location: Scarborough
Posts: 110

2013 Defender 110 Puma 2.2 DCPU Keswick Green

Thanks- this is the relay supplied with the loom. Can I simply replace this with a timer relay at the existing connection point on the loom?
I’m assuming, after the relevant time dictated by the relay (say 20 mins), it turns the heater off (whatever the switch position), and the heater only reactivates if the switch is toggled off/on again? That might be a simple solution and I just wire direct to battery.
Thanks

Click image to enlarge

13th Sep 2022 5:21pm

macfrank

Member Since: 05 Nov 2015
Location: somewhere in the north
Posts: 986

2015 Defender 110 Puma 2.2 SW Keswick Green

Well, you want to switch both seats separately I guess?

Then I see these alternatives involving relay(s):
a) one ignition-switched relay, two latching switches, one for each seat
b) a permanent live to two momentary switches, triggering two timer relays, one for each seat

a) works only with ignition on, heating as long as a switch is on
b) works even without ignition, but limited by timer and can be restarted by pressing a switch again

c) if you want both belts and braces you could use b) with an ignition signal instead of the permanent live, so the timers only work with ignition on

Remember, the relays are used to separate a low-current "signal" (thin wire, pins 85 and 86) from the actual power line to the seats (thick wire, pins 30 and 87) (polarity doesn't matter but there is a convention to connect + to 86, ground to 85, battery + "in" to 30, load + "out" to 87).

With a) the switches are in the power line branching from relay to each seat. So you have thicker wires to and from the switches, and the switches must be able to carry the full current (unlike some infamous automotive supplier's light switches I heard about

)
With b) the (momentary) switches are in the signal line to each relay, so they will carry only a small current.

For b) you may want to wire the switch's LED as a "tell tale" for the timer being on.
Now would be the time to draw a diagram

Don't forget fuses in the right places

15th Sep 2022 6:40am

ScarboroughSeadog

Member Since: 21 Jul 2022
Location: Scarborough
Posts: 110

Thanks- b looks like the most viable option at the moment. I’m working with two (one for each seat) pre-supplied looms from Exmoor Trim. Each has a relay and a switch, but each has only a single (fused) positive and negative connection (not separated battery and ignition switch connections).
I wondering if I can simply switch out the supplied relay for a timed relay at the existing connection point. I’ll try and post the wiring diagram when back home tomorrow.
Thanks.

15th Sep 2022 7:25am

mwestcrew

Member Since: 09 Dec 2019
Location: South Warwickshire
Posts: 216

Yes you could just swap out the relay. The timer gets it power from the load feed. These relays require just a pulse of 12v to energise and the timer does not start until there is no voltage at the trigger. 2011 130 Utility Body
2005 110 Van

15th Sep 2022 8:39am

mwestcrew

Member Since: 09 Dec 2019
Location: South Warwickshire
Posts: 216

I think using the original loom may not be ideal. It probably doesn’t allow getting trigger and load feeds from different sources. 2011 130 Utility Body
2005 110 Van

15th Sep 2022 8:42am

ScarboroughSeadog

Member Since: 21 Jul 2022
Location: Scarborough
Posts: 110

It doesn’t- I’ll just be wiring each loom into a single power source and earth.
I’ll have to try and work out what spec timer relay will be a drop in replacement for the existing relay. Any pointers on that?
Thanks

15th Sep 2022 8:51am

ScarboroughSeadog

Member Since: 21 Jul 2022
Location: Scarborough
Posts: 110

Click image to enlarge

Click image to enlarge

Photo of loom wiring diagram attached. I’m ideally looking for an ignition switched connection point under the drivers seat box (point 1). But that seems a surprisingly difficult ask, so the alternative would be to attach a timed relay at point 2, to replace the existing relay at that point (see photo of existing relay) ASSUMING THAT WOULD WORK? and wire direct to battery. If that’s a viable way to create a timed circuit I could use some guidance as to what spec of relay to look for in order to plug into the existing connection.

Thanks all.

16th Sep 2022 11:43am

ScarboroughSeadog

Member Since: 21 Jul 2022
Location: Scarborough
Posts: 110

Ok- I’ve given up trying to find a suitable ignition switched live to plug into in the under seat box. I can’t seem to find any clear direction on fitting a timer relay to my existing Exmoor trim loom either (and that is a second best option anyway).
I’ve decided to fit a piggy back fuse to the 20A fuse protecting the ignition switched lighter/accessory socket in the under dash fuse box, and feed the wire from there to the heated seat loom.

Click image to enlarge
That seems to be the only viable option. Good to see these threads concluded for those that come after, so I’ll update in due course.

21st Sep 2022 11:34am

macfrank

Member Since: 05 Nov 2015
Location: somewhere in the north
Posts: 986

Hi, I was offline for a while, so saw your diagrams just now.

I had now idea the seats had a two-stage heater ("ahh, luxury"

)
The relay provided is used to realise the two stages by wiring two heater elements (bum and back I guess) either in parallel (hot, red LED, relay not engaged) or in series (not so hot, green LED, relay engaged). Quite clever. So, this relay has nothing to do with decoupling an ignition signal from the power line and hence can't simply be replaced by a timer.

The relay/timer we were talking about would be in addition to the seats' loom - "left" of the Ub line in the lower diagram (which should correspond to a point behind the fuse in the upper diagram).

Apart from that, I think it's a good solution to tap off the lighter's power. Remember it's "on" in the ignition switch's AUX position, that's before the actual ignition position.

21st Sep 2022 5:37pm

ScarboroughSeadog

Member Since: 21 Jul 2022
Location: Scarborough
Posts: 110

Great stuff Macfrank- that's just the sort of electrical input I needed! All understood.

The most practical solution seems to be to go with a piggy back fuse from the cig lighter fuse in the under dash box, work that piggy back wire back to the underseat area under the mats etc, then wire up the loom as supplied.

Thanks

22nd Sep 2022 9:12am

ScarboroughSeadog

Member Since: 21 Jul 2022
Location: Scarborough
Posts: 110

Nice to finish of these threads for those that come after:
Wired a piggy back fuse to the cig lighter fuse in the under dash box, fed this to the under seat box through an existing grommet.
Took earth from the existing chassis earth point below the seat box
Wired in the seat connectors as per the existing loom.
Bingo- works a treat, and is ignition switched.
Also have switched live and earth in the under seat box now, if needed for anything else.
Thanks for all the help!

Click image to enlarge

26th Sep 2022 11:52am

macfrank

Member Since: 05 Nov 2015
Location: somewhere in the north
Posts: 986

thanks for the pictures; glad it works.

26th Sep 2022 8:22pm

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