ABS was an option on vans with these chassis - so there is a light on the dash if fitted, and no light if not - a separate red light that says "ABS".
See photo - the bottom left red light isn't fitted on non abs vans.
The ABS system fitted is made by Bosch. The control box for it is in the passenger foot well behind the trim and the fuse box.
The system is very reliable, and in practice in a motorhome, which is generally driven quite conservatively and emergency stops are quite rare, you can go for years without ever hearing or feeling it. Occasionally you will feel it in snow, on on a loose gravel surface.
When you turn the key, the ABS light will come on, and it should go out when the engine starts and the system self tests. If the light stays on, the brakes will still work as normal, but with no ABS.
When you turn the key, the ABS light will come on, and it should go out when the engine starts and the system self tests. If the light stays on, the brakes will still work as normal, but with no ABS.
The problem is that the MOT rules say that if fitted, abs must work. But the only indication to the tester is that the light comes on and then goes out. If it stays on, there is a fault, and the van fails.
I have seen several vans over the years where ABS is fitted, but not working, but the light has been taken out, or even modified so that it looks as though it's working when it isn't - just to get through the MOT - very naughty! This is usually because most folk have no clue how to fix these old ABS systems, and neither do garages.
However this isn't always the case. The commonest abs fault that makes the light stay on is nothing more than a £100 voltage control relay - an easy fix. The second commonest fault is the reluctor rings, and while Mercedes will scratch their heads and say "obsolete, no spares available", there are specialist companies that can supply them. There is a company in the UK called reluctorrings.com. The sensors on the wheels are also replaceable - you just have to find a garage who know these old vans.
See photos for more info.
I have seen several vans over the years where ABS is fitted, but not working, but the light has been taken out, or even modified so that it looks as though it's working when it isn't - just to get through the MOT - very naughty! This is usually because most folk have no clue how to fix these old ABS systems, and neither do garages.
However this isn't always the case. The commonest abs fault that makes the light stay on is nothing more than a £100 voltage control relay - an easy fix. The second commonest fault is the reluctor rings, and while Mercedes will scratch their heads and say "obsolete, no spares available", there are specialist companies that can supply them. There is a company in the UK called reluctorrings.com. The sensors on the wheels are also replaceable - you just have to find a garage who know these old vans.
See photos for more info.
Behind the fuse panel is the ABS control box (if fitted!)
Mounted on the left is the voltage control relay - this is the commonest reason for the ABS light staying on, and is easily replaced - a good tip is to find another owner and swap their relay for yours to prove if yours is faulty, before you order one.
If you don't have this red ABS light, lower left, then you don't have ABS!
This comment has been removed by a blog administrator.
ReplyDeleteHello... My 310~D Hymer judders when breaking when below about 2/3 MPH, as if the ABS is kicking in. Is this a fault. I read in a manual that the ABS wil lkick in always at that speed. I thought it was a fault, took it to Mercedes and they say a sensor is a fault. But I cannot source the sensor. The ABS light does not stay on. What can I do?
ReplyDeleteI am not an expert, I can only repeat what I have seen and heard over the years. I did have a van once that did that at low speed. Also on snow. The brakes have something called reluctor rings, which have gaps in them, a bit like a slotted wheel, and the sensor senses when the wheel has stopped, and then signals the control unit which pulses the brakes. But how this pulsing is achieved, I don't know - it has to be hydraulic. So it must either be a fault with the ring sensing mechanism, or the hydraulics. My money is on the first theory. There is a UK company called https://www.reluctorrings.com/ who appear to be the leading experts - who knows, you might get some free advice!
ReplyDeleteJoin "Classic Hymers Technical" on Facebook if you haven't already.
ReplyDeleteThanks for your help
ReplyDelete