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Intermittent direction blinker function

5868 Views 14 Replies 7 Participants Last post by  BBRT
Having done various searches I have yet to find a solution to this problem.
I travel to work each morning with no problem with the blinkers, however in the afternoons travelling back home there is no blinker function. It seems that this could be related to heat and the fact that the problem manifested itself after I disconnected the battery to repair the ecm fan.
Any suggestions? Thanks in advance.
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Try reseting the turn signals,
With the engine running turn on the hazard lights on for 10-15 seconds, then turn them off.
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Thanks leapyfish, I will give that a try.
Have a look at the foam block, next to the jack in the boot. See if it's damp.

It's protecting the pse brain and doesn't like damp/water.

When my pse failed the indicators played up, not in the same , but this is a quick and easy check.
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The heat may be making the either the relay in the ECU or the contacts in the stalk sweat ?
I am also having similar issues with the green arrows in the cluster and the turn/emergency signals burning solid rather than blinking.

This is all for Pre-FL R170...

The bulbs for the anti-theft alarm are different from the bulbs for the turn/emergency signals. I'm not 100% sure a failure of the PSE in the trunk can cause the "on but not blinking" scenario we both face (although the PSE often causes problems with other bulbs/filaments).

There are only three components that can blink the turn signal bulbs/filaments: 1) the turn signal switch on the steering column, 2) the red triangle, and 3) the lock confirmation relay. #1 and #2 receive a "blinking signal" from the CCM (in the apparatus box under the hood) and simply pass that on; #3 is controlled by the DAS module (not the PSE) and generates it's own blinking signal.

I've tried repairing the relay inside the CCM - this helped only for a few days. I've considered replacing the CCM and wiring an aftermarket flasher relay into the circuit. I've done neither yet.

I've also wondered if one of the above might be drawing too much current and causing the relay in the CCM to burn... replacing the CCM wouldn't fix that.
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When the pse was playing up I'd get one side on solid, then both.
It may not be this, but the check is easy.
Damp foam worth investigating further.
Dry foam and doubtful it's a problem.
Avel Du,

When your PSE was failing, what were the symptoms? Were the green arrows in the instrument cluster affected? Or just the lights outside the car?
Thanks for the replies so far guys. My problem was/is (it is working at the moment after trying leapyfish's advice) that there was no arrow lights blinking on the dash or the exterior direction indicators. Hazard lights work as well as the blinking when I lock/unlock the doors. This leaves me to believe it is the "blinking unit" or (unlikely) the stalk.
My blinking lights had been working for several days until I tried leapyfish's reset procedure... I pressed the hazard button, the lights all started flashing as expected, then 10 seconds later they all stopped blinking and came on solid - and I'm back where I started. At this point I'm still just trying to gather information about this particular failure.


Are you saying your red triangle works as expected (all four exterior bulbs flashing, both green IC arrows flashing) but using your turn signal doesn't? If that's right, do you get 1) no lights anywhere, 2) solid lights everywhere you expect blinking lights?
efair, when this problem occur, there is NO lights, no green arrow blinking or exterior indicators flashing. When I press the hazard button, I have the triangle red light flashing and all exterior indicators operating.
The red triangle and the turn signal switch both receive "blinking signal" from the same source (CCM) via Z30; if the red triangle is working, the CCM is probably OK. I'm speculating your turn signal switch, or the wiring to it, is broken.
Have you changed any bulbs recently? When I bought my car, the turn signals operated normally. When I turned on my headlights, all the turn signals lit up solid (even the signal on the side mirrors). Found out later that the previous owner replaced the signal bulb with a wrong bulb. The replacement was a single filament not a double filament bulb. Replaced with double filament bulb - problem solved.
That's a great addition to the thread - thanks!

I bet your symptom was solid though, not intermittent...? And I also bet your previous owner put the wrong bulbs in the front corners - those should have two filaments as you mention (one for the blinker, one for the parking/standing lights). I bet putting the single-filament bulb was shorting these two circuits. That would explain your behavior at least.
Alot of these problems are caused by the intermittent operation of a relay in the pcb box under the bonnet (hood), the one next to the battery.
The relay is on a pcb that cost big bucks (part no.1708200926).

I think there is a post on this forum or the 170 DIY forum below that links to a thread on that shows a fix. However I cannot find it today.

Try this link to Benzworld "".

I cleaned the relay contacts with a slither of 2000grit wet & dry and some contact cleaner.

The exercise is not for the fainthearted. However the cheapest pcb board I could find was $350 on ebay, to fix an issue that on any other car would cost just a $7 relay.
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