E31 hazard switch not working

[EHO850]

Hi everyone - I am new here and hope to receive some advice here - I appreciate you reading this!
I purchased an E31 (M70) Manual transmission that actually runs perfectly. It came with some little electrical problems that I mostly have solved now. One stubborn issue is that the hazard switch does not work and I need to see this fixed in order to be able to pass the Quebec safety inspection.

The connector that connects the hazard switch to the wiring harnas was in total shambles (somebody used brute force and threw half of the connector away ) I had to figure out how to connect the switch to the wiring harnas. I soldered 4 wires and a nice new connector to the switch.

The hazard switch has 4 connections numbered 2,3,4,5 and according the electrical schema should be connected like: .
pin 2 - open (?)
pin 3 - ground - brown
pin 4 - power (?) - grey/red
pin 5 - to hazard lights - blue/green - this powers the bulb in the switch

The observation is:

• With mounted crash relay all indicators blink together and cannot be turned off. Although the hazard switch does turn off its internal blinking light when switched off.
• without mounted crash relay the left and right indicators work. Turning the hazard switch on/off does not start the 4 way blinking.

The switch is new. I can measure the resistor connected to pin 4 and the resistance of the light bulb.
The hazard flasher relay is new, the crash control module is new.

My idea is that the wire coming from pin 2 or 4 is broken/shortening somewhere hence my questions:

• Does somebody have a schematic of the internals/electronics of the hazard relay and/or the crash relay so I can determine my next steps?
• Does somebody have an idea what (else) can be wrong or where to look?

Any suggestion/advice is appreciated!
thanks!
Emile

[revtor]

Remove the N17 crash control module (crash relay). With the hazard switch in the normal (off) position, measure the voltage between pins 6 and 8 of the crash control module socket. It should read 12 V. Then measure the voltage between pins 6 and 7 of the same socket. It should read 0 V. If you get 12 V, pin 7 is pulled low while this should be impossible with the hazard switch in the off position (bad wiring?). If you got 0 V, measure the voltage over pins 1-8 and 6-1. What do you get?

On the removed module measure resistance between pins 5 (+) and 8 (-). What do you get?

[EHO850]

Thanks Revtor!
Currently I simply removed the crash relay and bridged pin 5 with pin 7 on the equivalent positions of the socket. This is where the hazard switch signal comes in. So no bad wiring here and the hazard switch now functions. I measured both crash sensors. They show OK with each 0 Ohm on one pin and 10 k Ohm on the other.
Regarding the voltages (hazard switch off):
between 6 and 8 -> 12V
between 6 and 7 -> 0 V which is correct because of the hazard switch pulling this to ground.
voltage over pin 1 and 8 -> 0 V
voltage over pin 1 and 6 -> 0.04 V
the module resistance between pin 5 and 8 is 13M Ohm (another relay shows 16M Ohm)

[revtor]

The static voltages are okay. When you write "another relay shows 16M Ohm" does that mean you have two crash control modules? And both show the same behavior? In that case we can rule out the crash control module (for now).

You have also confirmed there is no wiring issue between hazard switch and K16 hazard flasher relay. If the N17 crash control module is fine, the only thing I can think of is the A1 general module (GM) pulling pin 1 low on the crash control module. Sadly we cannot draw conclusions from the measurements as pin 1 appears to be floating without the crash control module inserted (measures 0 V to power and ground).

[EHO850]

Thanks Revtor. You are correct;I have 2 crash modules. Question is what causes them to generate the 4 way alarm if all inputs are correct. 1 relay was newly purchased, the other came with the car. I can measure the GM module pin 1 - eventually place a pullup resistor like 4.7 kOhm to 12V and see if this is actively low or high. Would you know what it should be? Also the schematics that I have might reveal what it should be. I will place my findings later here.
Thanks again!
Emile

[EHO850]

With a pull-up resistor, pin 1 of the crash relay socket measures 12V so active high. According to the electrical troubleshooting manual this should be between 0 and 2 Volts (ground pulse during crash). Looks like a transistor went to heaven or the GM crash situation is triggered. Would there be any electronic schematics of the GM available or any idea what would trigger this?
Thanks
Emile

[revtor]

No, 12 V is correct under normal conditions (with a pull-up resistor). What the Electrical Troubleshooting Manual means is that during a crash pin 1 is briefly pulled low by the A1 general module (GM). I'll try to confirm the voltage with my E31 later today.

Can you do the same test with a pull-up resistor to 12V on pin 2 of the N17 socket? That's the input from the N1 anti-theft control module (DWA). It can also activate all indicators. The expected voltage is not described in the ETM but after looking at pictures of the N17 crash control module PCB, its input seems to be a mirror of that of pins 1 (GM) and 7 (hazard switch). Thus the correct voltage with a pull-up should be 12 V.

If pin 2 is correct as well, I'm baffled at what's going on.

In that case I think we'll have to test the N17 module even though you have two of them and it's rather unlikely both are faulty.

Update: Tested on my E31... With a pull-up resistor pins 1, 2 and 7 read 12 V under normal operation.

I've taken the time to trace the PCB of the N17 crash control module. If you'd like I can draw a diagram but I'll need some time for that.

Anyway, operation is really simple:

Pin 6 is power (12 V) and pin 8 ground.

Pin 5 is an open collector output. When it's active it pulls pin 5 to ground. Output pin 5 becomes active when input pins 2 (DWA) or 7 (hazard switch) are low. Pin 1 (GM) is a special case. It feeds a R/S flip flop to form a latching input. A (low) pulse on pin 1 activates output pin 5 and it remains active even when pin 1 returns to high. The only way to reset the output is by briefly activating the hazard switch (pin 7).

Pins 3 and 9 are drawn in the ETM as if part of a relay but in reality they are simply connected. No further circuits are attached to these pins in the N17 crash control module.

Pin 4 is unused.

Note that while pulling and re-inserting the N17 crash control module, I noticed that sometimes all indicators started blinking upon re-insertion. This could be stopped only by brief activation of the hazard switch. This is obviously caused by the R/S flip flop. This is probably also why the indicators sometimes start blinking when the batteries are reconnected. Thus when the indicators blink after re-inserting the module, it does not necessarily mean there's something wrong with it. Always briefly activate the hazard switch to make sure you're not fooled by this scenario.

[EHO850]

Pin 2 is low (0.01 V) indicating the anti-theft circuit (DWA) is triggered. I am getting an appreciation for the way this car's electronics are setup!
Following the schematics reveals that this can be triggered by various lights (doors, trunk, hood, glove box) and ...... the radio! Since the radio was not attached when I bought the car I guess we can conclude this mystery and I can say a valid lesson learned!

P.S.
I anticipated that the radio would be one of the last projects on this car. I will see that the radio gets connected or otherwise see that the switch is not triggered.
Thanks so much Revtor and what a great forum!!

Emile

[revtor]

I know the DWA radio contact is shown in the Electrical Troubleshooting Manual (ETM) for all years, but to be honest I have never seen it. It's certainly not present on my E31. Maybe it was omitted in later years without updating the documentation? If you do find it, can you make a picture or describe where it is?

Anyway, even if the contact is present on your E31 I don't think it is your problem. I assume you unlocked the car (how? with the key in the door lock or with the remote control)? In that case the DWA should be disarmed and none of its inputs can trigger the alarm. And even if the DWA is armed, it should react only to changing inputs. For example, you can lock your car and arm the anti-theft system with the hood open, the windows down, the glovebox open,... and all the car should do is rapidly blink the DWA LED in the center console for 10 seconds. That's the indication something is not properly closed. The horn will not sound, nor do the indicators flash but the DWA system is armed and will monitor the inputs (probably only those that are properly 'closed').

[ctuls]

This thread inspired me to figure out what is going on with my hazards:

Symptoms:

1. Hazards only work when button is depressed down. i.e. when released hazards stop flashing
2. When battery was reconnected the hazards came on and I had to press the button to the hazard button to turn them off

I measured:

between 6 and 8 -> 12V
between 6 and 7 -> 0 V
voltage over pin 1 and 8 -> 0 V
voltage over pin 1 and 6 -> 0 V

the module resistance between pin 5 and 8 is 1.1K Ohm. Which seems different than what others have


Wanted to check if there was any advice or anything else I should check.

1. Is a replacement crash module needed?
2. Is the hazard switch in the car supposed to toggle between depressed and not depressed when pressed? Mine spings back up

[revtor]

ctuls: I would first focus on the hazard switch. Yours seems to be broken. It should be a toggle switch - not a momentary switch.

Remove the N17 crash control module. With the hazard switch in the off position, measure continuity (resistance) between pins 7 and 8. It should show no connection (open circuit). Press and release the switch and measure continuity between pins 7 and 8 again. Now it should read a short circuit. If you still have an open circuit, the switch is bad.