Help wanted - Lighting Control issues

[Phenex]

Main Beam not staying and Side lights stay on even after turning off switch, sounds like a relay is getting stuck in the control unit, any ideas how to fix?
Does anyone know what this relay is stuck on the side of the control unit.

[Phenex]

Added some annotation to the spliced wiring as suggested by Alex.

[Juddder]

Hi Jason

Great - so here's the pin out for the Lights ECU with the colours labelled on it, cropped out of the main wiring diagrams



From your photos we can see that

B9 = Blue / White - Positive Output to Main Beam (Red 2)
A9 = Red - Positive Input Battery (Red 3)
Black - Assume GND

and then the ones that are hard to see from the photo

A1 (?) = Red / Yellow - Positive Input Dip (Red 1)
A6 (?) = Yellow / Red - Positive Output to Dim/Dip (Centre wire)

From the relay photos we can see that it is a Lucas SRB501 normally connected from 35/51 to 87A and switched on power from 35/51 to 87 with 85 and 86 acting as the switch inputs

So if you can continuity test the connections from the relay to the pins on the white plug and verify which ones they go to, then we can work out what is switching what

I'll go and find the datasheet for that relay as it will show the orientation of the terminals which means we can map wires to relay connections

[Juddder]

SRB501 from the Lucas Datasheet



Therefore

30 = Red 1
87a = Red/Yellow middle
87 = Red 3

86 = Red 2
85 = GND (Black)

So Red 2 (86) is switching the relay from the middle Red/Yellow (87a) to Red 3 (87) and the output when switched is fed from Red 1 (30) being the power line

[Juddder]

BTW If the side lights are staying on, even with the switch off, then it's continually wired to +12V which could be either part of this relay or just another wiring splice

Side lights output is A3 - Red / White

[Phenex]

You are correct with the Relay pins.

I have continuity checked them:

30 = Red 1
87a = Red/Yellow middle - to A6
87 = Red 3 to A9

86 = Red 2 to B9
85 = GND (Black)



Sorry for not great photo.

[Phenex]

Just trying to clarify how think the logic for Full Beam works (there must be a similar logic for Fog Lights).

[Juddder]

What would make most sense to me was if 87a was connected to your side lights (this would explain why they are on all the time) and 87 was connected to your main lights.

This would mean when the light switch dial is turned to main beam, the main lights turn on and the side lights turn off

Can you measure which pin 30 (Red 1) goes to as that is the bit we need to know next?

[Phenex]

Pin 30 (Red1) goes to Red/Yellow Cable on the DIP/DIM Unit.

[Gladers01]

Phenex said:

Pin 30 (Red1) goes to Red/Yellow Cable on the DIP/DIM Unit.

Check if there is voltage on pins 85 & 86 when switching from side lights to headlights, the relay coil needs to be energised to allow the contacts to switch from normally closed (when off) to normally open (closed when the coil is energised) you may be able to hear the relay click.

[Phenex]

Plan on checking Friday

On the meantime have replaced the defective relay in control unit (hoping my soldering is up to scratch)

The issue is still there, if I remove the sidelight fuse the main and full beams work properly.

Don't know if this is relevant but the small lights in the lower headlight (full beam unit) Don't illuminate with the sidelights. Could blown bulbs cause this issue.

Edited by Phenex on Tuesday 1st April 10:22