Adaptive cruise control radar unit needed

**philsayer** · 18-05-2011,10:54 AM

Apparently, the reason I'm seeing "ACC Sensor Blocked" whenever I try to use my cruise control is that the radar unit has drowned - the dreaded water ingress has rendered it useless.

A new one is (wait for it) around £2200. (Yes, over two grand - not a typo!)

Now, this isn't the sort of thing that Halfords will have an own-brand version of, so it'll need to be a previously-cherished unit. Any hints as to where I might start looking?

(A8 3.0TDi 2005, pre-facelift)

Temporarily, I'm using the cruise control that the good Lord built into my right ankle, but I really miss ACC.

Any help gratefully received... and as an afterthought, does the water in the housing definitely mean the radar unit is on its way to landfill? The tech (non-Audi) wasn't certain. (Clutching at straws here!)

**Sam** · 18-05-2011,11:09 AM

A drowned CCM (common in Passats of a similar era) can be recovered with a spot of drying and contact cleaning.

Can you get the current unit out and inspect it yourself?

**philsayer** · 18-05-2011,11:29 AM

Thanks for that - I'll certainly give it a go! Cheers.

**Sam** · 18-05-2011,12:08 PM

Even if it doesn't work, you're still £2.2k lighter for now

I've successfully dried/cleaned three drowned CCMs and all of them are still working now.

It all depends how long it's been submerged. Rusty contacts can be resoldered but rusty/perished PCBs aren't as easy.

**philsayer** · 18-05-2011,12:21 PM

I'm confused - (it doesn't take much...) I can see heaps of CCMs on eBay for paltry amounts... and for various VAG cars. Are we definitely talking about the same module? I think I need the radar sender/sensor behind the bumper. Or are they both called CCMs?

**Hex69** · 18-05-2011,12:30 PM

Originally Posted by philsayer

I'm confused - (it doesn't take much...) I can see heaps of CCMs on eBay for paltry amounts... and for various VAG cars. Are we definitely talking about the same module? I think I need the radar sender/sensor behind the bumper. Or are they both called CCMs?

No they're not the same.

What Sam's saying is that the CCM module for Passats had a habit of being submerged due a fantastic design flaw and with careful drying out they were made to work again.

He's suggesting that you take your radar unit off the car and try to careful dry it to see if that will restore it to full health. You've got nothing to lose.

Hope this helps.

**Hex69** · 18-05-2011,12:33 PM

is this what you need?

http://cgi.ebay.co.uk/Audi-A8-D2-Cru...item1e62b5cad5

**philsayer** · 18-05-2011,12:36 PM

Sometimes I can be amazingly dim... my thanks to you both for clearing that up! Just had a look - it's Bosch unit, the dome I mentioned doesn't appear to lift off, and it looks like the metal housing that contains the clever bits is held in place by clips. But access is hard due to the bumper's shape. I'll get it on a ramp or axle stands and have a look from underneath. Thanks again.

I'm pretty sure that isn't the part on eBay - I think Audi refer to it as a radar sensor, rather than control unit. I just spoke to the parts dept at Blackburn Audi - they actually have one in stock! I wonder how many they shift in a week?