indicators flash too fast.

[stickandrudder]

I've got one of those mystery jobs that is proving a bit difficult to solve!
The indicators flash to fast, both left & right. Hazard flash speed is OK.
year 2000 210 chassis.
things tried so far:
All bulbs & holders swapped
N10 (front sam) renewed
PSE unit swapped
Alarm siren renewed.
Mirrors swapped.
Indicator switch renewed.
Resistances across wires at N10 checked: all OK

Straws I might clutch at:
Door SAM. I tried disconnecting the repeater lamps on another car and it does not introduce this fault so am incliined to dismiss door SAM.

EIS. The supply for the front SAM comes via the EIS, but since the flashers are obviously working I'm disinclined to suspect this.

There is a towbar fitted but we've disconnect the wiring to no avail.

I'm getting desperate and was hoping someone here might have had similar issues?

Thanks in advance

 

[Alex Crow]

hello s+r, have we already been involved in this one? i know it came up on the forum before, perhaps it was this one.

does the car have a mercedes towbar fitted? if so, check the microswitch just inside the socket, it may be stuck which could cause this problem.

 

[television]

We have had 2 post on this in the last few weeks,,I am still at a loss to find much info on it

 

[stickandrudder]

The micro switch is a good suggestion. I'll check it tomorrow thanks.

 

[stickandrudder]

It's not the microswitch.......

 

[speedybiker]

Have you maybe got a bad earth at the indicators?

I would try earthing with a lenght of cable to see if thats whats causing it

Alex.

 

[Alex Crow]

It's not the microswitch.......

did you find it then? under the hinged cover, placed to be contacted with a plug fitted. this would only be on the mercedes original equipment tow bar, and is wired into the pse unit. how can you be sure the microswitch is ok?

 

[stickandrudder]

We removed the wiring for the tow bar!
We've also tried running a substitute earth cable straight to the battery from the headlamps but since the resistances in the circuit from the front SAM to the bulbs are OK I was not surprised when this didn't change anything.
I've been doing this stuff for 30 years and it's not often I'm beaten!

 

[Alex Crow]

removed the towbar wiring? this will only work if the microswitch is usually in the open position, if it makes a circuit when not pressed, and goes open circuit when pressed then you have proved nothing. the reason i press this point is that i have known this fault only once on a modern car (a 1999 w202), and it was caused by this very microswitch. the switch is wired to the pse unit which cans the "towbar lights in use" message to the front sam. i suggest you disconnect the pse unit (under the rear seat next to the battery) and try it again. all this assumes that you do have the MB towbar fitted. another possibility is a faulty pse unit. as the flash speed signal is generated by the front sam you have ruled that out, also the flash speed should be independent of the current load, ie if half the bulbs were blown the speed should be the same.

 

[stickandrudder]

Thanks for your continued input.
I've tried both swapping and disconnecting the pse unit but will take another look at the tow bar micro-switch in the morning.
(you can tell that I'm really bugged by this because I'm here at 11.45pm!)
I'll also see if I can find the wiring diagram for the towbar on WIS, unless someone can give me the relevant doc number...........

 

[DMRobinson]

Flasher relay? Dont know anything about the specific model, just a thought

 

[stickandrudder]

With respect I suspect that you haven't read the rest of the thread!
Thanks for your thoughts anyway.

 

[television]

Thanks for your continued input.
I've tried both swapping and disconnecting the pse unit but will take another look at the tow bar micro-switch in the morning.
(you can tell that I'm really bugged by this because I'm here at 11.45pm!)
I'll also see if I can find the wiring diagram for the towbar on WIS, unless someone can give me the relevant doc number...........

AN31.19p-8080-03FFB

 

[stickandrudder]

super stuff, thanks!

 

[stickandrudder]

Mr Patient you have managed to crack it!!
It was indeed the micro switch and thanks to TV for the reference to the document.
I'm a bit long in the tooth and it always takes me ages to find anything on WIS.
Well done to both of you!!

 

[Alex Crow]

happy days, i am glad i insisted on it! so sorry that you got there the long way round, but all is well that ends well.

 

[television]

happy days, i am glad i insisted on it! so sorry that you got there the long way round, but all is well that ends well.

And thank you Alex I would have never worked that one out.

 

[Alex Crow]

yes, it is one that you just have to know .

 

[stickandrudder]

The irritatng thing is that I have a £100,000 per year wage bill and I still had to do it myself, even after passng on the initial tip.

 

[television]

The irritatng thing is that I have a £100,000 per year wage bill and I still had to do it myself, even after passng on the initial tip.

Never trust anyone,, I am terrible in this respect, that is why I could never employ anyone and stayed working on my own