Heated WIndscreens and Side Demisting

Last winter’s driving wasn’t a great deal of fun.  I had plenty of freezing fog to deal with on my early drive to work, and scraping the windscreen at 0400 while trying to avoid waking the neighbours is bad enough, but to have to do so every fifty yards until the engine warms up is ridiculous.  Since we seem to be getting a bit more freezing winter weather (like when I was a child – don’t get me started on this global warming rubbish!), heated screens seem less a luxury and more a necessity.  They certainly proved valuable on the 90 last winter and occasionally on the RRC in previous years until removed.

I bought a pair of screens from Devon 4×4.  The total cost was £260 – not a cheap option, but only £8 dearer than the cheapest alternative.  The beauty of the D4x4 choice was that they are sent in a wooden box with copious amounts of card, foam and bubble-wrap protection, so damage is extraordinarily unlikely.  To fit them, I removed the top dash padding as this makes access to the retaining strip screws far easier.  It also allows tidier routing of the wiring inside the dash, through the plastic grommet just left of centre of the bulkhead top rail.  The glazing is fitted in the same manner as normal, but you do have to allow space at the bottom of the screen for the wiring to fit behind the retaining strips.  Using the square foam pads from the packaging works well for this as it ensures the right clearance at the bottom, centralising the glass neatly and getting it level within the frame so that the visible edges of the foil strips along the top and bottom are even within the frame.  I did need to trim the bottom 1/4″ off the centre vertical retaining strip to clear the inboard wiring, which is what was fed through the bulkhead grommet to the switch output.  The outboard wires cleared the retaining strips without modification and were connected to the windscreen clamp lower bolts for earthing (you’ll see the black wire behind all the coloured roof accessory wiring in the photo below).  To power the screens, I used the 20A Carling Tech switch previously used for the heated wing mirrors (hooking them up to the heater rear screen circuit like most manufacturers do), allowing a direct feed to the screens which consume 18A.  The switch is fed from the auxilliary battery via a 20A fuse in the Defender type fuse box under the lower dash.

The dash was refitted and the Defenderdemisters installed.  This took a small amount of alteration, as the units are designed to fit the larger demister slots of later pre-Puma Defenders rather than the small slots of the SIII and early 90/110.  This required the removal of the locating tabs from the demisters (which would fit into the slots of Defenders) and the trimming of the SIII demister trim to sit flush rather than proud of the dash top.  I did try aligning the centres of the new vents with the existing slots, but that doesn’t work – the side duct of the new units are too long and if you cut them down, they’d point at the door frame rather than the glass.  So, they had to be sited off centre of the slots, with their ends flush with the dash ends, but this is still fine as full flow is still achieved and the internal vanes of the new demister ensure good flow direction.  I had to drill screw holes through the top of the dash into the top rail of the bulkhead, using the included screws through the new vents’ holes to mark the screw hole positions in the dash top for drilling.  Once installed, a little fettling of the position of the vent fore or aft over the slots fine tuned the proportion of air flow diverted from the front screens to the side windows – this would be pre-determined by the locating tabs on the Defender, but on an early vehicle, moving the vent further towards the windscreen will divert more air to the sides, and there is enough clearance on the screws in their holes to allow a reasonable adjustment.  Unfortunately, I found the outboard ends of the trims tended to sit high, a couple of mm off the dash top.  Double sided number-plate tape didn’t stick well enough, so I resorted to drilling a third screw hole and fitting self tapping screws through the vent tube into the dash top, which is the reason for the rubber grommets next to the venturi slots near the outboard ends. Hopefully, others won’t have the same issue, but it’s a simple thing to fix.  I did look at neater screwing from underneath, but the dash ends can’t be fitted or removed with the vents in place, so screwing the ends down from on top seemed the only solution.

I now just have to wait for suitable weather to test their effectiveness, but with the amount of airflow through the side vents and the reports of others about the windscreens, I’m confident that I should have very good visibility this winter.


Edit:  a few uses in recent over-night foggy conditions have proven both systems work well, though the demister vents need full fan speed to keep the side window fogging at cleared.

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  1. Hi Nick,

    Good to see you’ve got the heated screens fitted. Probably the best modification I’ve done to the hybrid, I think you’ll be pleased with them when the time comes.

    I’m glad to see that the defender demisters fitted without too much fuss, I will have to invest in a set of those for the Td5. Now the weathers on the turn I’d best get around to fitting the heated mirror kit, if I can tear myself away from the Para Recce project for a bit that is.



  2. Hi Nick,

    I fitted the Defender Demisters some time ago and experienced the same problem of the edns sitting too high. You brought up a nice solution fitting a third self tapping screw, I am going to try this also.
    Thanks for so many inspiring Land Rover reading,

    Regards, Vincent

  3. Hi Nick,

    Long time no speak! I’ve been popping in every now and then to check on your 109″ and I remain very impressed.

    I look forward to finding out how you get on with both the heated screens and side demisters. I’m just at the stage of getting my dashboard back together in my 88″ and am designing the demister system. Curiously though I never had any issues with demisting in my wifes 109″ over the last couple of winters. I’m guessing that the small space of her truck cab allows the heater to do its job? If so I may not have an issue with mine which is also a truck cab but we do plan on fitting a hard top to my wifes 109″ shortly along with seats for the kids (copied off your layout 😉 ) and I guess that extra volume will show up the shortcomings of the heating and demisting.

    Anyway, keep up the good work.


  4. Hi Ian,

    Truck cabs heat up much better than hard tops, especially 109s. I also have the handicap of a Tdi, which takes a fair while to warm up from cold.

    I did get a change for a basic try out of the new screen and side demisters the other morning, where it was just damp and tepid enough to cause the windows to start fogging slightly with the whole family (dogs included) in the car. I’m happy to say that it all works.

  5. Edward Parrott says:

    Hi Nick, what did you use to fit the screen with, OEM rubber strip or something like Sikaflex? I need to change screens on both mine, only standard for now though, might buy heated screens in the future though.

  6. Hi Ed

    I used double sided neoprene tape, basically a roll of numberplate sticking tape. It works well, its downside being that it’s a bit if a pig to remove when replacing screens.

  7. Edward Parrott says:

    Thanks Nick, hoping not to be having to remove it too often!

  8. Hi Nick
    The heater in my 109 hard top doesn’t seem too bad – admittedly my girlfriend has bought a nice thick blanket specifically for when she’s in the Land Rover, and we’ve not hit the deepest of winter yet, but I am definitely going to have to fit a radiator muff. Heated screens……… Do these have very fine wire / elements running through the glass as seen in more recent vehicles with factory fitted heated screens, or, is it just the visible strips at the bottom & top??
    Many thanks 🙂

  9. Hi Kurt.

    The heated screens have a foil strip between the laminates along the top and bottom, mostly but not completely hidden by the frame. They have the fine wiggly vertical elements, but they really aren’t noticeable unless you look for them, even with bright oblique lighting at night. I find them invaluable now.


  10. Hi Nick

    Many thanks for this info! 🙂 – so they are a fully heated screen then.
    I was tempted to try putting a thin / narrow copper tape strip top & bottom on each screen & energising these from a relay to see if this had any frost melting effect – because that’s basically what rear heated screens are / were. Chances are it would have minimal effect only at the copper tape…. or…… catastrophic!

    I may give it a whirl on a spare screen just to satisfy my curiosity.

    Thanks for the info


  11. Kurt, if you run power through strips from one end to another, you’ll just be causing a short circuit that could damage your electrics or even start a fire. The filaments have resistance, which is what causes them to heat up – a strip of copper will not have enough resistance. If you plan on having one strip powered and the other earthed to see if that works, then you’ll be disappointed. For the cost of these screens, it’s not worth messing about. They’re not cheap, but they hardly break the bank at a little over £140 for the pair.

  12. Hi Nick

    not going to have one strip powered & one earthed. All things that I have fitted so far namely front spots & reversing lights are correctly fused. Cabling & also relay used is overrated – if I remember correctly the cable is rated at about 17A & carrying quite a bit less (fuses also rated less than the cable, but a little more than the load).
    Heated screens are on next summers to do list, and that way I can fit them a bit more leisurely & plenty of time to ensure there is no leaks prior to relying on them. Also as you said – not a deal breaker at the price of them. For this winter a radiator muff will suffice – & thankfully the temperature gauge is working ok. So far I think I am relatively lucky in that the heater is ok to good, as far as a standard one goes & clears the screen reasonably well.

  13. The standard heater can be OK if in good order. Using bicarbonate of soda solution to descale the inside of the matrix clears it well and makes it far more efficient, especially if you remove the matrix from the housing to clear out all the accumulated rubbish (you’ll be amazed at what you find in there – mine had a snooker ball as well as many nails and a few Biro’s). Making sire the fan casing is in good order, aging any rust holes and ensuring the ducts and flexible hose to the matrix are leak free makes the world if difference, too. A cheap and sime aid to heater output is to use domestic foam pipe lagging from tour local DIY store to insulate the steel pipes along the head.

    As for the electrical side of heated screens, I agree that the power draw doesn’t justify a relay, but you do need a reasonably heavy duty switch and appropriate wiring. I use Carling Technologies Condura switches for most of my accessories, and they’re rayed at 20A, so plenty of capacity for one switch to run the front screens in parallel, and another to run the rear screen and wing mirror heaters together.

  14. Hi Nick, so I’ve just had a Pilkinton heated windscreen fitted to my 110 200tdi.
    No wiring look though so I want to know if I can use a regular spot light wiring loom or piggyback on the rear demister screen loom.
    What my cheapest most effective solution?

    Many thanks


  15. Hi Ewan,

    You need to check the current of the screen to determine the switch you can use. I would suggest the spotlight loom, usually incorporating a relay, would be up to the job, but I wouldn’t recommend spurring from the rear screen system – you don’t want to use the front screen more than necessary as it causes the elements to fail, leaving patches unheated. It is a good idea to have a warning light i plain view to indicate the screen is on so that you remember to switch it off, or fit a timed relay. Even with timer relays, I find sections of the screen burn out prematurely, so overriding the relay and switching off manually once the screen is clear is a good idea.

    Hope that helps.

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