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Brake Warning Lights in the rain

wobbly

MB Enthusiast
Joined
Aug 3, 2004
Messages
1,529
Location
Middlesex
Car
2018 GLC 220d AMG line Premium + 1989 500SL Now sold, replaced with 2007 Aston Martin DB9
I have a problem with my 2000 ML 320.

The problem is that the BAS/ESP malfunction, ETS malfunction, ABS malfunction, and Brake fluid level low, warning lights and audio warning all come on but only in heavy rain, or when the car has been through a automatic car wash.

I have checked threads on this site, and have changed the brake light switch which seems a common problem, but still the same, checked and cleaned all the wheel sensors, but again no change. the warning lights have not been on for months as we have had no heavy rain but yesterday as soon as it rained they came back on.

So today I thought I would investigate further, as the problem seems to be electrical/brake and rain connected, I thought I would soak each wheel hub using a hosepipe and drive the car after soaking each wheel. I did this and not a single warning light appeared. I dont know what to do now, so any any ideas would be appreciated.

If all fails the car is booked in for service in ten days time, I will ask them to look at it.

Thanks in advance Wobbly
 
The trouble is that all these function are linked as part of the brake system protection. A fault on any switch/relay/sensor in the system will trigger the fault lights, either one or all of them. The only way to resolve is to put the car onto the computer and find out which part is failing or reacting to the water. So ask the dealer when you have the service.
 
Hi,

Normally a water leak behind the driver's side front wing, allowing water ingress around the pedal / A pillar area. Normally requires removal of front wing to sort.

regards,

Job
 
Hi,

I have had the car serviced, and reported the problem to the garage.

The problem coded as the brake modulatoc/control unit. They checked this unit and found it was working correctly, so they checked the electrical connections to the unit and found them to be slightly corroded and discoloured.
So they have cleaned the connections, and have secured with cable ties a plastic bag over the unit to stop the ingress of water.

Just have to wait for some heavy rain to see if the problem is solved.

Wobbly
 
As I said above, it proves it can be any part of the electronic brake system.
 

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