Suspect the N10 combination relay may be intermittent. Symptoms are listed in my earlier post...

W140 Sudden Electrical Gremlin, any ideas?

Is intermittent failure possible with this relay, or does it fail completely? Does anyone know how to test this relay? 1995 S600.

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1995 S600, 1 of 618 (sold)

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The description and operation might give you insight into your problem.

I would agree with JimF. I think you have voltage issues. Have your alternator tested and your battery tested with load.

Description and Operation w140 Combination Relay...



Functions

Turn signal flashing
Hazard warning flashing
Turn signal flashing in hazard warning mode
Hazard warning flashing when anti-theft warning system (ATA) triggered
Turn signal flashing with trader
Wiper system
Heated rear window
1. Turn signal flashing
The "left" or "right" flashing is actuated by separate wiring.

The turn signal indicators are actuated from terminal 15 (fuse 15, fuse box F3 in the fuse and relay box F1) by means of the combination switch (S4) and the combination relay (N10, N10/2).

The indicator lamps in the instrument cluster (A1) are actuated from the output of the combination relay (N10, N10/2) and the rear turn signal lamps via the connector, taillamp harness (X18).

The front turn signal lamps are actuated by the connector, taillamp harness (X18) via the connector, headlamp harness (X24).

On various national versions, contact is made at the front turn signal lamps with auxiliary turn signal lamps which are installed in the fenders.

If a bulb is faulty, the flashing frequency is doubled, in addition the failure of a bulb is indicated by the exterior lamp failure monitoring unit (N7).

Actuation is controlled by the combination relay (N10, N10/2) connector assignment 17 to the exterior lamp failure monitoring unit (N7) connector assignment 15.

2. Hazard warning flashing
The hazard warning flasher system is switched on and off by the hazard warning flasher switch.

When the hazard warning system is switched on, the integral resistor (38.3 Ohms ) in the hazard warning switch is connected in ahead of the voltage signal. As a result of the difference in voltage compared to the battery voltage, the electronics in combination relay (N10, N10/2) detects that the hazard warning system has been switched on.

When the hazard warning system is switched off, the resistor is bypassed (equal to battery voltage). The hazard warning switch is illuminated via the combination relay (N10, N10/2) connector assignment 10 and a bulb.


3. Turn signal flashing in hazard warning mode
When the hazard warning system is switched on and the key in the steering lock is in position 2, the respective turn signal lamp (right or left) is actuated when the combination switch (S4) is operated. The hazard warning system does not operate during this time.
4. Hazard warning flashing if anti-theft warning system tripped
The hazard warning system is actuated by the anti-theft warning control module (N26) by contact 2 to the combination relay (N10, N10/2), 21 - pin connector contact 1.

When the anti-theft warning system is tripped, both turn signal lamp outputs are actuated with twicy frequency. The indicator lamp in the hazard warning switch remains off when this happens.

The hazard warning function and the turn signal flashing are retained.


6. Wiper system
The following functions of the wiper system are actuated in the combination relay (N10, N10/2):

Intermittent mode
Touch wipe
Follow-up wipe
Continuous wipe (fast and slow)
Blocking protection
Automatic wiping speed reduction
The wiper stages are activated by fuse 15 (terminal 15R), wiper system relay K26 and by the combination switch (S4). In the intermittent mode and for touch wipe the combination relay (N10, N10/2) is actuated voltage-coded by various resistors fitted to the combination switch (S4). The third wipe stage is actuated without the pre-connected resistor.

The wiper system features a blocking protection. The wiper motor cycle is monitored by terminal 31b. If a cycle lasts longer than 12 - 15 seconds , the wiper motor is switched off electronically.

The wiper system switches back one stage automatically when the vehicle speed decreases as follows:
to less than 20 km/h (up to 03/94),
to less than 5 km/h (as of 04/94 to approx. 07/94).

The wiper system switches automatically to the stage set on the combination switch when the vehicle speed increases to above:


25 km/h (up to 03/94)
8 km/h (as of 04/94 to approx. 07/94).

The wiper system is switched back from fast continuous wipe to slow continuous wipe, or from slow continuous wipe to intermittent wipe, or from intermittent wipe to slow intermittent wipe.



7. Heated rear window
The heated rear window is actuated by terminal 15R, fuse 15 via the pushbutton switch (S14) to the combination relay (N10, N10/2), 21-pin connector (contact 6). The load current is conducted by the fuse box (F2 fuse 6) to the 8-pin connector at the combination relay (contact 7) via the power output terminal 87 to the heated rear window.

The electronics of the combination relay (N10, N10/2) switches off the power output of the time-delay relay of the heated rear window if:


No voltage exists at terminal 15R,
Battery voltage is below 10.6 V .
In this case, the function lamp in the pushbutton switch (S14) flashes.

The heated rear window is switched on again automatically as soon as the voltage is 0.6 to 1 V greater than the cut-off voltage.

If the heated rear window is switched on and off four times within 60 - 64 seconds , the power output terminal 87 is switched off and the function lamp in the pushbutton switch goes out. The heated rear window switches off automatically after an operating period of 15 ±5 minutes .

The visual signal is actuated via terminal 58d and by means of a LED in the pushbutton switch.

__________________
Russell McMahon
Tulsa, OK
2001 CLK 320
1992 400se
1993 400e
2000 320ML