Got out in a bit of snow tonight heading back into London on the M40. Nothing settling but flurrying around in the air. Anyway got a bong on the old adaptive cruise while at 70, red triangle; "driver intervene" it says but there was nothing in front, I'm thinking what's going on here? Then yellow warning says "radar unit blocked" and it won't go back into cruise.

If anyone knows this approach into west London it goes from 70/national limit, to 60 and then the average speed cameras start around that bit where the limit goes to 60. Worried about the average cameras here, I'm pressing on the cruise button, but I keep getting the yellow warning, no cruise available and - god help me I'm trying to maintain 60, then 50 after Northolt - with just my right foot! This is not the luxury I am accustomed to!

Turns out keeping a steady speed manually requires a crazy amount of attention, there's no doubt that attention is better spent on checking emails or something ONLY JOKING - better spent eyes the road rather than obsessive over the speedo. And sure enough whilst all this madness (!) was going on I see a small creature make a run for the centre reservation - I think it was a squirrel. I swerved, probably shouldn't have (only from a safety swerving POV).

Anyway, back to the radar, the wipers were on but the snow wasn't built up on the screen or anything so I'm not sure what caused the confusion. Maybe 10-12 mins later once on the 40mph section on the elevated Westway it decided I'd been through enough and came back in to take that workload off me.

Moral of the story: you only appreciate something like adaptive cruise when it's gone.

Sidenote: I did enjoy a boot of the right foot along the on ramp (+ a bit), mashed the pedal into the deep pile for a quick italian with a clear road ahead - that second turbo winds up a treat and although it's redline is relatively low, it sounds lovely over 4000rpm. The rate of climb through the revs via the 8-speed is absolutely sensational. The noise although subdued I'd describe as smooth yet menacing. That 4.4TDV8 is so torquey at low revs but geez it can shift in the upper numbers with those twin turbos blowing. Love it.

Not sure that squirrel will make it off that central res. Best of luck little guy.

. Cheers, Greg
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2011 Vogue SE 4.4 with lots of toys in Stornaway

Sensor is behind the bumper below the passenger's side headlamp. Maybe you had a layer of snow build-up on the bumper face (snow in the UK is wet, therefore 'sticky'?? Regards,
Mick

'Bertha' - 2014 SDV8 Autobigraphy
'Vincent' - 2010 TdV8 Vogue SE
- 'Molly' - 2005 HSE Auto
'Dixie' - 2000 D2 Td5 ES

Mine's sensor is on the RHS but no chance of snow blocking it in today's 42C at 3pm.
The 5.0 has a sensor each side.

Oh I thought it was top of the windscreen?
. Cheers, Greg
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2011 Vogue SE 4.4 with lots of toys in Stornaway

Nope that's the rain sensor for wipers. Radar unit is further down as others have said. Even dirt can cause it not to work.

its in behind the bumper, left as you look at the front [i think]

Ah yes, sure enough - there it is item no. 8.

So how does it get blocked? There's no lens as such?

.

Click image to enlarge

I don't know how it works on the FF but if it is genuine radar it doesn't need or have a lens. John
2008 Stornoway Grey 3.6 Tdv8 Vogue
2005 TD6 Java Black Vogue - Written off!!
GAP iiD BT
2003 Discovery TD5 Auto, Nanocom Evolution - gone to a new home!
MasseyFerguson 152 - No electronics!! - Sold

A build up of mud or snow in front of the radar module used to upset mine on my Sport. Drove me mad on long journeys upon the A1 when it was difficult to overtake on single lane parts of the journey. Current: FF Westminster money pit

Gone:
RRS 4.2 SC
RRS 3.6 TDV8
FL2 TD4

I had the same warning on the way back from Norwich on the A11 on Wednesday night. When in services I saw the grill was caked with snow and cleared it which resolved the issue. After 15 back on the road I had it again. First world problems indeed !!!!

gonna_go_double_r wrote:

Sidenote: I did enjoy a boot of the right foot along the on ramp (+ a bit), mashed the pedal into the deep pile for a quick italian with a clear road ahead - that second turbo winds up a treat and although it's redline is relatively low, it sounds lovely over 4000rpm. The rate of climb through the revs via the 8-speed is absolutely sensational. The noise although subdued I'd describe as smooth yet menacing. That 4.4TDV8 is so torquey at low revs but geez it can shift in the upper numbers with those twin turbos blowing. Love it..

I enjoy doing the same. In Sport mode too  2011 4.4 TDV8 Vogue SE Buckingham Blue with Ivory and clear glass = "Rory"
New Defender D300 90 on order so "Rory" will be going to a new home....!
1974 Series 3 Lightweight = "Millie"
My preferred specialist: www.glenrands.co.uk
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I had this last night as well, on a 6 hour snow filled drive from London to Dorset.There was definitely lots of snow/slush getting thrown up last night though, and having read this thread before, was half expecting to see it!

Lost cruise control somewhere around Farnborough, just before I hit the enormous set of traffic on the M3 around Basingstoke...

A few hours later though it was all okay again once we were moving .

It uses radar (high frequency radio waves) so no lens required. Radio waves will travel through the plastic of the bumper cover without problem, but will be attenuated by the bumper being coated in WET snow or dirt. If the attenuation is high enough, the system software will assume no signal and shut down the system.