Author Topic: emergecy flasher unit under dash  (Read 1775 times)

Green68MB

  • Associate Member
  • Junior Level
  • *
  • USA, NC, Taylorsville
  • Posts: 21
emergecy flasher unit under dash
« on: September 24, 2021, 14:08:30 »
How do you remove the emergency flasher unit under the dash to test if it is functioning.   ( 1968 280SL)    Fuse # 5 is operating, as are the stop and reverse lights. The fuel  reserve gauge is not, but I believe that is a broken wire issue.   Any suggestions would be appreciated. Thanks

lpeterssen

  • Vendor
  • Gold
  • *****
  • USA, FL, Miami
  • Posts: 592
Re: emergecy flasher unit under dash
« Reply #1 on: September 25, 2021, 11:19:10 »
Dear friend

First have a multimeter handy, leave the flasher unit connected, but separate a bit it’s Bakelite connector from the harness to check each of the leads.

Below attached on this post you will find a picture of the back of the standard Bosch flasher used on most mercedes of the era.  Double check that you have the same unit, as position of the pins may be different if not this particular model.

There are 6 pins.

This is what you should be looking for:

1. Terminal labeled 15, should have power only with ignition on
2. Terminal labeled 30, should have power all the time
3. Terminal labeled 31, should have continuity with chassis ground

Then you have the output terminals,

First, there are two terminals labeled “L” and “R” which are the output signals for the left and right turn lights when you activate the hazard relay for an emergency.  Pull up the knob of the flasher relay with ignition off and see if you have a pulsed 12v signal on each of these leads..  for that put your multimeter in DC voltage on a range close to 12V (50volts for example) which is what you are looking to measure. Put multimeter negative lead on a good ground and the positive lead use it to touch the flasher terminals L & R.

Now if above test was successful go for testing the flasher  turn signal function.  That function needs the terminal 15 to be energized, and the steering wheel switch should be activated pointed towards the LEFT or RIGHT.  Ignition ON in order to have power on terminal 15. 

Put your multimeter positive lead on the terminal labeled “49a” of the flasher, keep your multimeter negative lead on a good ground and see if you have a pulsating 12v signal.

Enjoy your experiment.

Best regards
L.peterssen

lpeterssen

  • Vendor
  • Gold
  • *****
  • USA, FL, Miami
  • Posts: 592
Re: emergecy flasher unit under dash
« Reply #2 on: September 25, 2021, 11:20:40 »
A better picture this time

lpeterssen

  • Vendor
  • Gold
  • *****
  • USA, FL, Miami
  • Posts: 592
Re: emergecy flasher unit under dash
« Reply #3 on: September 25, 2021, 11:47:10 »
Dear friend

A better way to do all these instructions is to open / remove the back plate of the connector attached to the hazard/emergency flasher relay.

In that case you will see the cable/lead Colour attached to each pin.

Here after a list of the cables and what are each of them for:

1. Terminal “L” cable BLACK/white
2. Terminal “R” cable BLACK/green
3. Terminal “49a” cable BLACK/white/green

4. Terminal “31” ground, cable BROWN
5. Terminal “15” switched 12v, cable BLACK/RED/GREEN coming from fuse 5
6. Terminal “30” always hot 12v, coming from fuse 1, cable. RED/WHITE

Best regards
L.peterssen

Green68MB

  • Associate Member
  • Junior Level
  • *
  • USA, NC, Taylorsville
  • Posts: 21
Re: emergecy flasher unit under dash
« Reply #4 on: September 26, 2021, 19:54:20 »
To LPeterssen, Thank you,  I will print all this and find an auto/electrician.

lpeterssen

  • Vendor
  • Gold
  • *****
  • USA, FL, Miami
  • Posts: 592
Re: emergecy flasher unit under dash
« Reply #5 on: September 27, 2021, 21:05:42 »
Your welcome mr green