Tim4x4

Tim4x4

Well-Known Member
Having fitted a heated front screen now to complete the wiring.
I do intend to complete the installation with the same safeguard as LR used. That means fitting a relay, controlled by a timer and the timer only able to switch on when the engine is running. Using an oil pressure switch.
Looking at the wiring diagram the oil pressure switch controlling the earth on the timer and the switch controlling the oil pressure warning light are of the same type.

My question is "Did LR install two oil pressure switches on the vehicle or did one switch control both?"
 
As you are switching to earth on a very low current circuit, as far as I can see there should be no problems combining the two, especialy as the relay will only requite an initial 'pulse' for it to latch.
 
Oldseadog said:
As you are switching to earth on a very low current circuit, as far as I can see there should be no problems combining the two, especialy as the relay will only requite an initial 'pulse' for it to latch.
Click to expand...

That is how I was looking at the problem.
 
Oldseadog said:
Remember that you are switching to earth. ;)
Click to expand...

Yes that is how I have wired the circuit the oil pressure switch will allow the timer to be earthed. When the switch is activated on the dash the timer will activate only when the oil pressure switch has supplied the earth to the timer.
Using a timer to regulate the length of time the HFS is switched on, the timer switches a relay to allow the feed to the HFS.
It is the earth to the timer the oil pressure switch will be making.
The timer is an electronic unit which draws 80mA when activated.
Will all be OK if I add this to the existing oil pressure switch leaving the original wiring in place.
In effect the factory fitted oil pressure switch will be serving two circuits?
 
If you are using the switch to earth the relay it will only work until the iol pressure liight goes out.

I will see if I can do you a diagram tomorrow or Friday.
 
Oldseadog said:
If you are using the switch to earth the relay it will only work until the iol pressure liight goes out.

I will see if I can do you a diagram tomorrow or Friday.
Click to expand...

Please do not all agree but I must be a numpty.
I believed the oil pressure switch when up to pressure completed a circuit by connecting to earth but am I wrong and it breaks a circuit by disconnecting from earth when up to pressure causing the light to go out????
If that is the case then my planned installation will not work.

Is the oil pressure switch used in the heated front screen circuit different and works in the opposite way:confused::confused::confused:

Any help on this would be great.
 
use smart relay as used on caravan touring electrics or split charge system
 
fanatic said:
use smart relay as used on caravan touring electrics or split charge system
Click to expand...

Thank you for the heads up on the relay, I have looked at the smart relays I see how they will work for my HFS great.
I do intend at a later date to fit a second battery and an inverter no towing electrics required. Second battery to run the inverter only.

New question can you recommend a suitable smart relay that I can use?
Lots of differing specifications and prices ranges from affordable £13.00 to ridiculously expensive £290.00.
 
Why not simply fit either a pre-set or an sdjustable timer relay which would switch on when you turn your ignition on?

You could even control it from a switch on the dash! ;););)
 
Oldseadog said:
Why not simply fit either a pre-set or an sdjustable timer relay which would switch on when you turn your ignition on?

You could even control it from a switch on the dash! ;););)
Click to expand...

What I wanted to achieve was a similar set up to the factory installation of a heated front screen without the high cost of factory timer £120.00.
The factory installation will not allow the timer to start without the engine running thus the alternator is charging. This is achieved by the use of an oil pressure switch I believe the part number is the same as the oil pressure switch controlling the oil warning light on the dash.
With my lack of electrical knowledge I believed the oil pressure switch completed an earth circuit when up to pressure but I have now been informed that it is the reverse it breaks the circuit when up to pressure.

I have almost completed the installation which would have created an earth to the timer only when oil up to pressure (if I had been correct with the way the switch worked) and was asking could I run both circuits off one oil pressure switch.

Now I am looking toward using a smart relay, if that means changing the installation so that the timer receives a live feed only when the alternator is charging I can easily achieve that.

At a later date I will be installing a second battery and an inverter so the smart relay will be an ideal piece of equipment to keep the second battery charged without compromising the main battery for starting.

Using a smart relay to control the feed to the timer seems a good solution to my problem, currently I have

l The screen is in place
l Timer installed (adjustable from 2min to 20min and able to interrupt when on)
l Switch and warning light installed in the dash (momentary ON - OFF - ON)
l Relay to switch power to the screen installed 70A (factory fit part)

What I now need is information on a suitable smart relay, I do not know how reliable they are. With the wide price range I do not want to get the cheapest because it is the cheapest but likewise I do not want to wast a lot of money on something not required.


The second battery and inverter will be a permanent installation and used throughout the year, the HFS on the other hand will be used only in winter.
 
lofty69 said:
Got any info on what you did exactly? Want to fit one to mine. Cheers
Click to expand...

First of all I collected information from the lads on LZ as follows:-

1, early heated screens have 3 contacts which heats 2 zones left and right sides
2, later screens have 2 contacts the heating element covers the whole screen.
3, both use only one relay
4, both use a timer to auto switch off the heater element after aprox 5 minuets
5, both can be switched off prior to the timer completing its cycle or reactivated directly after the cycle
6, too ensure the screen cannot be activated when the alternator is not charging an oil pressure switch is used. This switch connects the relay to earth only when there is sufficient oil pressure e.g. the engine is running
7, the screens are rated at 40 amps
8, the LR fitted relay is rated at 70 amps (giving some safety margin)
9, both 2 and 3 contact screens are available in clear and tinted
10, screen prices vary considerably Pilkington glass is standard fitment and an after marked product is available made by Pilkington's (advised some cheaper options would be a poor choice)
11, sealing rubber prices vary considerably some cheaper options are of a poor shape do not fit correctly from day one potentially it can let in water from day one. The use of a sealing compound stops it but only for a short period of time LR supplied rubber is good quality
12, BE AWARE if you were to supply a LR sourced seal to a fitting company (to ensure you get the good seal fitted) asking them to use it instead of their own it may invalidate any warranty they give.

Using the above information I had a local replacement windscreen company fit new screen Pilkinton’s and used the sealing rubber they supply. Manufacture of the rubber unknown but I did inspect it prior to installation (roll of eyes from the fitter you know the “we have one hear look”) but who cares I am paying not an insurance claim.

The timer from Maplins Kemo Time Switch Module Code N83QL £19.99 fitted this under the passenger seat. I also fitted an additional fuse box so that other equipment can be installed but this is is not necessary just for the HFS just pick up your power from a suitable point.

As the LR fitted HFS timers were controlled by an oil pressure switch I wanted to do the same but issues with how the oil pressure switch worked stopped me from doing that. I decided to use a smart relay as suggested by fanatic in a previous post.

The smart relay I used was Ring Smartcom Combination Relay £19.99 this allows the power to the timer only when the alternator is charging so the HFS cannot be used without the alternator charging.

Switch to operate mounted on the dash is from Maplins 10A Toggle Switch DPDT Momentary on-off-on Code N41KR £3.59.

The relay was from Land Rover PRC7303 £18.41 Mounted behind instruments near to the screen to keep high power wires to a minimum length.

That is about it the rest is routing the wires I did this under the vehicle in protective trunking and sealed the ends to stop water ingress when all was fitted up and working.

I hope this is some use to you
 
I've done a couple of heated screen installs on TD5 Defenders - there was no engine off protection as you describe.If its for your own car then its not really worth bothering to fit this feature,as you would be aware of the warning lamp in the switch,plus how often would you leave the ignition in position 2 without running the engine ?
http://www.ebay.co.uk/itm/Defender-...arts_Vehicles_CarParts_SM&hash=item564fa33b0c

May help....
 
Last edited:
eightinavee said:
I've done a couple of heated screen installs on TD5 Defenders - there was no engine off protection as you describe.If its for your own car then its not really worth bothering to fit this feature,as you would be aware of the warning lamp in the switch,plus how often would you leave the ignition in position 2 without running the engine ?
Defender Td4 & Td5 heated front screen wiring kit genuine switch YUG000460LNF | eBay

May help....
Click to expand...

The engine off system is as facrory instalation, I have coppied the LR opperation of the HFS.
I do not have an answer to your question as how often would you leave the ignition in position 2 without running the engine? but it is possible and if the warning lamp failed it is likley.
As long as you know the consequenses you can wire it up any way you want even straight to the battery with jump leads if you want.
It is your choice.
 
Tim4x4 said:
The engine off system is as facrory instalation, I have coppied the LR opperation of the HFS.
I do not have an answer to your question as how often would you leave the ignition in position 2 without running the engine? but it is possible and if the warning lamp failed it is likley.
As long as you know the consequenses you can wire it up any way you want even straight to the battery with jump leads if you want.
It is your choice.
Click to expand...
I suppose its down to how much you need your hand held,both of the customers cars I did last winter have just enjoyed the clear screen first thing on a cold morning and been sensible enough to switch them on only when needed...
 
eightinavee said:
I suppose its down to how much you need your hand held,both of the customers cars I did last winter have just enjoyed the clear screen first thing on a cold morning and been sensible enough to switch them on only when needed...
Click to expand...

I do not see it in the same way as you it is not having my hand held but it is completing the installation correctly.
Having your hand held as you describe it is something car drivers need for example,

  • indicators which flash automatically, changing from on to off
  • indicators that self cancel after making a turn
  • thermostat that automatically opens to allow the coolant to circulate at a set temperature
  • windscreen wipers that self park
  • brake lights that come on when you apply the foot brake
  • reversing lights that comes on when reverse gear is selected
  • the list could go on and on
Each one of the above operations could be completed manually by a sensible driver but this only makes driving more of a chore. The more equipment installed as a driver the more you would have to do.
Even on the basic Defender many operations are interlinked to make the driving experience simpler (if the design engineer is holding my hand thank goodness).

On the more modern cars like a new Range Rover many operations are interlinked and ECU controlled. There are more byte's of data being processed each second by the on board ECU's on a new Range Rover than an F17 fighter plane. The reason for this is so that anyone can drive them you do not have to get a university degree and spend seven years training in simulators prior to getting out on the open road or off road for that matter.
 
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