Flasher/Hazard Mods on my 80SC

[targa80]

Still in the process of installing harnesses and buzzing out each circuit. When I started working on my 1980SC Flasher/Hazard circuits this week I noticed several issues. My 80SC has the Hella four contact relay P/N 003425-02 and it was fully functional when I removed it back in 2002 time frame.

The following issues were noted:
1) Signal indicators on Tach were dimly lit with ignition on.
2) Using the turn signal switch caused both Tach indicators to toggle between dimly lit and brightly lit in either turn setting. External directionals worked properly.
3)With ignition off and Hazard switch selected both Tach Indicators were toggling between dimly lit and brightly lit. External directionals worked properly.
4)In all three cases above the turn/hazard flasher would shortly after being energized start to buzz. This noise was caused by the flasher relay making and breaking contact rapidly (chattering)
5) The Hazard Switch was not illuminated when the light switch was pulled to the parking/internal light position.

I did a search on Pelican and found many post where the diagnosis was to replace the 4 post Flasher /Hazard relay. It seems that there are several manufactures and several part numbers with varying cost associated with them.

The below schematic is relevant to the 80SC and as you can see boxed in red for the Tach indicator lights to function properly when operated the terminal (C) on the turn signal relay provides an internal connection sinking to ground on terminal 31.



In my case terminal (C) was not sinking internally to ground but was suppling 12v and this causes the two Tach indicator lights to be constantly dimly lit and all of the associated issues noted. In my particular case it seems that transistor T4 on the flasher circuit board had internally shorted.



The below schematic of the 1985 Flasher/Hazard circuit shows that the circuit was modified to not use Terminal (C) on the Flasher /Hazard relay. The two Tach indicator lights are now tied directly to the ground terminal G116 in the luggage compartment. Do you think Porsche realized that the original circuit design was overkill?



I researched on the internet where I could purchase a replacement relay and realized none were available in my local area. I would need to mail order from our host and I did not want to wait for a delivery to fix my relay problem, Instead, I opened the relay and unsoldered the terminal (C) contact and removed it from the relay housing. Thusly removing the 12v source causing the indicator lights to be dimly lit. I added a ground wire from terminal (C) on the relay socket in the luggage compartment to the local ground terminal. I did this because the BL/WH wires from the Tach indicator lights are still attached to terminal (C) on the relay socket and this makes the mod easily reversed if I acquire a replacement 4 post Flasher /Hazard relay in the future. This mod resolved the first four issues noted above.

Also, it should be noted that the local auto parts stores sell a Tridon Novita 3 post Flasher relay P/N EP36 that has the same three terminals (49) (49a) and (31) and works in the modified circuit.

In the case of issue (5) above, I found that the 150 ohm resistor connected at terminal (58) on the Hazard Flasher switch in the 80SC schematic was terminated and not connected to terminal (58a) on the light switch. This prevented the hazard light from being illuminated and dimmed with he rest of the dash lights. I don't know if this was a factory mod but it did look like it was professionally done. I corrected the wiring to provide illumination of the hazard light when the light switch is enabled. It should be noted that the light is dim and is for visual recognition at night. When the Hazard switch is engaged the hazard light becomes bright and flashes in sync with the other lights.

[fanaudical]

Very well done article - I used this info to fix my blinkers today and get the dash indicators to work correctly. Thanks for the write-up!