Car electric problem

[roadrunner]

Mercedes estate E-Class 1993, one circuit developed a problem.

The relay in the boot gives a loud buzzing sound and the back wiper doesn't work, while the relay is buzzing the number plate lights come on.

I realized that the back wiper works only while at leat two doors are open including the boot.

The circuit takes 16 AM fuse, on the same circuit are (rear door locking system, central locking system, door lights, reading lamps the trunk light, safety belt handover arm, aut. antenna).

I have almost covered all cables in question and I understand it is impossible to guess, hope someone might have had such or similar experience that would shed some light.
Thanks

 

[jj4091]

If the relay in the boot controls any of the items you are talking about I would have thought it was highly likely you just need a new relay.Is there another one on the car somewhere else with the same ratings, if so try a swop.

 

[roadrunner]

Hi jj

I have replaced the relay twice "second hand", all of them worked (clicked), once I shut the doors all relays omitted buzzing noise.

Thanks for quick response.

 

[iain90210]

Have you checked the earth strap for that circuit?

 

[yes2mud]

I agree with iain90210,this problem sounds like a poor earth return,which is improved by opening the doors.

 

[roadrunner]

Once I slammed the estate rear door shut and the problem started.

Almost exposed all components at rear especially the door, checked all visible connections, for a minute I thought the earthing on the electric antenna was suspect, when wiggled the group of wires, the central locking some how activated, the rear wiper and the relay remain the obvious problem.

Also to mention that when the doors are shut and the rear wiper switch is on, the combination switch on the facia gives a dim light while the relay is buzzing.

excuse my ignorance, each component is earthed individually, would the earth strap be different? if so, would it be close the relay & components.

Thanks

 

[jonnyfishing]

R.R.
Sounds to me like you have a few broken wires in the bunch that comes from the top of the car roof to the tailgate,usualy in a long rubber grommet. It is caused by the action of the tailgate opening and closing. If this is the problem, don't just rejoin them, solder and insulate new lengths to all wires(about 6 inches) in so you have the new lengths where it flexes.

 

[^neo^]

Has it got a remote boot popper? Ie: press a button and the boot opens.

 

[roadrunner]

Hi

Thanks to all for your brilliant responses.

Jonny, you are spot on.

Today, I have found the fault, as Jonny mentioned, was punch of cables in a long rubber grommet, couple of wires were severed including the earth cable, located on the top left hand side between the corner of the car roof under the lining and the tailgate.

I fixed them using straight connectors and all is working fine, if ever reoccurs I'll change wires.

Thank you once again