Rain Light Sensor (RLS) - Intermittent wipers not working

[rule1110]

Originally Posted by Clavurion

You are so focused on those sensor readings even though the ISTA screen shot clearly tells you that wiper motor grounding rest position signal is missing on the rain sensor and those linked diagrams were to guide you what to measure with multimeter.

Good point, I'll have a look at the wiper motor today and see if I can test it. Any tips on how I would do this? Would I have to locate '2' on the wiper motor, put the multimeter on it then engage the auto wipers and spray the sensor to see if a signal is sent when the sensor is wet?

[Clavurion]

Originally Posted by rule1110

Good point, I'll have a look at the wiper motor today and see if I can test it. Any tips on how I would do this? Would I have to locate '2' on the wiper motor, put the multimeter on it then engage the auto wipers and spray the sensor to see if a signal is sent when the sensor is wet?

Like i said on my earlier post if the wipers with normal wiper activation are doing a full sweep and stopping in the correct end position that switch is working correctly. So there is no need to investigate the switch.

In this case that signal is not routed to rain sensor correctly. So the rain sensor does not know if the wipers are still sweeping or in the neutral rest position. Measure the voltage and resistance to ground on that rain sensor pin 4 (brown/green wire) and see if the values change according to wiper position. Then if needed check the continuity from that pin to wiper motor switch and body module (GM3).

[rule1110]

Originally Posted by Clavurion

Like i said on my earlier post if the wipers with normal wiper activation are doing a full sweep and stopping in the correct end position that switch is working correctly. So there is no need to investigate the switch.

In this case that signal is not routed to rain sensor correctly. So the rain sensor does not know if the wipers are still sweeping or in the neutral rest position. Measure the voltage and resistance to ground on that rain sensor pin 4 (brown/green wire) and see if the values change according to wiper position. Then if needed check the continuity from that pin to wiper motor switch and body module (GM3).

I was able to check the voltage by back probing pin 4 with the positive and back probing pin 2 with the negative. With the wipers parked I get reading of 9.8 volts. When I operate the wipers on demand with a single wipe the voltage drops down to 0.5 volts then returns back to 9.8 volts when they stop. I tried to measure the ohms but multimeter wasn't able to pick up anything, it just gave a reading of 1.

[Clavurion]

Originally Posted by rule1110

I was able to check the voltage by back probing pin 4 with the positive and back probing pin 2 with the negative. With the wipers parked I get reading of 9.8 volts. When I operate the wipers on demand with a single wipe the voltage drops down to 0.5 volts then returns back to 9.8 volts when they stop. I tried to measure the ohms but multimeter wasn't able to pick up anything, it just gave a reading of 1.

On rest state that voltage is produced by GM3 measuring circuit and when grounded the voltage drops so it sounds like the line is working correctly. (Though I've never measured what that voltage should be exactly.) But is ISTA still thinking that rain sensor is not seeing it working correctly? Is there a tab on rain sensor live data/status page showing the switch position? (I don't remember if there is one on rain sensor diagnostics. On GM3 there is a tab showing wiper motor switch position.)

On rain sensor coding options there is one parameter regarding this switch function.

WISCHERMOTOR_RSK
wert_01 or wert_02
wert_01 is correct on E53/E39 and wert_02 on E46
I assume this difference is because these vehicles use different type body module (perhaps different voltage produced by body module on that sensing line).