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.