A-Class Electrical Problems

[Richard Murray]

Hi

My wife's A-Class (1999 T-Plate), 168 model, 1.6 injection has started playing up. Fault started with car failing to start - which was attributed to a faulty battery (which has now been replaced). Also the rear wiper remained on all the time. To stop the window glass becoming scratched - I've disconnected the rear wiper at the socket after removing the trim in the tailgate.

Today - the front window washers refuse to operate, the rear window element won't work (no tell-tale light on button) and the CD player won't play CDs shows [error] in the Blauplunk display. Also when you try to operate the front window washers - [SRS] supplemental Restraint System displays in the dash. I don't think this is connected to the airbags or seatbelt pre-tensioners. Incidently - the window washer pump doesn't sound, so it has to be electrical - and not simply a loose connector hose or blocked water jet.

Before I take the car to a Bosch specialist (not MB stealership) I assume this is a faulty relay or poor earth connection - can anyone point me in the right direction please. Thanks [Television] for advice to date.

Richard

 

[malcolm E53 AMG]

Sounds very much like a relay problem. You will need to find out the functionality of each relay, there will be a common denominator which hopefully will include the group of electrical equipment you have mentioned.

 

[Richard Murray]

Are all the relays situated in the fuse box under the floor? By the way - I checked all the fuses and they were fine, and the [+] and [-] terminals are clean and tight.

 

[malcolm E53 AMG]

Sorry can't help with the location of the relays as I have no experience of the A class. You will need to refer to a Haynes manual or similar if you are to find out the fuctionality of each relay, they will be listed by function. If you do remove the relays clean the pins with switch cleaner or similar to make sure you have good contacts, slight corrosion in itself can cause problems.

 

[c320]

I think you may have blew a sam unit. On a c class, there are three and each control certain electrics.

THis happened to me after i disconnected the battery on my w203. Same results, a number of feautres woudl not work and the car would go into limp mode as soon as i drove.

Cost me £330 or so to fix.

I was advised by a dealer that the battery on a modern mb must under no circumstances be touched and should only be replaced by an approved techie.

 

[television]

Hello, the fuse relay box is under your seat.
Some of your symptons could be to replace fuse 14 with a fuse module, this effects rear wiper and front washers and the SRS indicators and rear demister(do not use 15amp fuse)
that should clear most of your faults

Re CD the laser pick up has gone down either you have an exchange radio unit or you find out who does the repairs at your local MB dealer, and they can fit a new pick up.

Any more info I need exact model nunber

Malcolm

Part number 000 000 00 16 09 effect cars < 05 10 99

 

[Richard Murray]

Sorted!

Replaced fuse for rear window demister, fitted new washer pump and rear window wiper motor. All problems fixed (79,000 miles on T-Plate), apart from multi-changer on Blaupunkt CD - think this is a recurring fault.

In addition to new exhaust and battery, it's been an expensive couple of weeks.

 

[television]

Replaced fuse for rear window demister, fitted new washer pump and rear window wiper motor. All problems fixed (79,000 miles on T-Plate), apart from multi-changer on Blaupunkt CD - think this is a recurring fault.

In addition to new exhaust and battery, it's been an expensive couple of weeks.

MB do give a warning NOT to use a fuse in 14 but the module instead to stop these faults from recuring.It was important enough,thats why I sent you a personal message

Malcolm

 

[c320]

Replaced fuse for rear window demister, fitted new washer pump and rear window wiper motor. All problems fixed (79,000 miles on T-Plate), apart from multi-changer on Blaupunkt CD - think this is a recurring fault.

In addition to new exhaust and battery, it's been an expensive couple of weeks.

glad to hear it mate - you want too see the problems i am having and how much money i have spent to date

 

[Richard Murray]

Hello, the fuse relay box is under your seat.
Some of your symptons could be to replace fuse 14 with a fuse module, this effects rear wiper and front washers and the SRS indicators and rear demister(do not use 15amp fuse)
that should clear most of your faults

Re CD the laser pick up has gone down either you have an exchange radio unit or you find out who does the repairs at your local MB dealer, and they can fit a new pick up.

Any more info I need exact model nunber

Malcolm

Part number 000 000 00 16 09 effect cars < 05 10 99

I spoke to auto-electrician at John R Weir [Main Dealer] and he had no experience of relays failing on A-Class. However he did say washer pumps and wiper motors were main source of problems. Regards the rear heated windscreen - when I checked the fuse, the 10amp fuse [under-rated by 5amps] had blown. Should be 15 amp fuse here - so I installed. I'll follow up regards your recommendation for fuse module instead of fuse to stop any recurring problems. Installed used parts from Dronsfield MB.

Thank you.

 

[television]

This is not a relay, its a standard mod to your car, its a module to stop the faults from reaccuring. MB do stress the point that a straight fuse should not be fitted.

<Malcolm

 

[jimsinessex]

Just to satisfy my curiosity, what is a fuse module and how does differ physically from a fuse?

Jim

 

[television]

When a fuse is used in the form of a module, it means that other components have been added and it is no longer a straight fuse on its own, it may have a cap wired across it to remove spikes for instance, resulting in a lower value fuse that will not blow in odd or unusual conditions.

Hope this helps Jim

Malcolm