Help - MOT Fail on Headlamp levelling Control

portculisz4 · Post by **portculisz4** » Fri Sep 17, 2021 5:38 pm

Just got my car back with a failure, the fail comments were
- Headlamp levelling device inoperative (offside) and Headlamp aim too low (offside)
I assume they mean the beam angle controlled by the thumb rotary control, can anyone tell where this device is located and the nature of its operation. I guess its electric, is a motor or a sort of relay.

bigwinn · Post by **bigwinn** » Fri Sep 17, 2021 5:53 pm

You car have xenons?

portculisz4 · Post by **portculisz4** » Fri Sep 17, 2021 6:16 pm

No, it has rthe standard bulbs for the headlight

bigwinn · Post by **bigwinn** » Fri Sep 17, 2021 6:20 pm

Righto- just helps to know to remove the fault being with the levellers connected to the suspension on xenon light set ups

Headlamp too low is a simple fix and can be rectified using screwdriver- no drama

Headlamp levelling device inoperative- when you move the headlamp adjustment switch on the instrument panel, do both headlights move up and down if you shine the beam on a wall?

portculisz4 · Post by **portculisz4** » Sun Sep 19, 2021 10:13 am

Sorry for late response (at Goodwood Revival yesterday). The beam on the offside seems to be stuck low and does not move when operating the thumb wheel, the nearside does move up and down. I suspect that the offside beam is out of spec because the leveling device is holding it down

enuff_zed · Post by **enuff_zed** » Sun Sep 19, 2021 11:42 am

portculisz4 wrote: ↑Sun Sep 19, 2021 10:13 am Sorry for late response (at Goodwood Revival yesterday). The beam on the offside seems to be stuck low and does not move when operating the thumb wheel, the nearside does move up and down. I suspect that the offside beam is out of spec because the leveling device is holding it down

That makes sense. So the next question is: dodgy connection or knackered motor?
'Umfaan' is breaking a Z at the moment, but not sure if it has the right bits for you?

portculisz4 · Post by **portculisz4** » Mon Sep 20, 2021 8:54 am

Thanks for the response. I guess the motor is adjacent to the headlamp unit and will need the plastic liner inside the wing removed to check, I am about to do that this morning.

enuff_zed · Post by **enuff_zed** » Mon Sep 20, 2021 8:55 am

portculisz4 wrote: ↑Mon Sep 20, 2021 8:54 am Thanks for the response. I guess the motor is adjacent to the headlamp unit and will need the plastic liner inside the wing removed to check, I am about to do that this morning.

Fingers crossed it's a bad connection and a simple fix.

portculisz4 · Post by **portculisz4** » Mon Sep 20, 2021 11:06 am

Thanks for your response. Have removed plastic under wing cover and also headlamp cover revealing the small motor inside the headlamp unit. This does appear to work when operating the headlamp thumbwheel but the headlamp assembly does not move. There appear to be two beam adjusters on unit itself one fed but a flexy stainless cable (on the outside of the unit), this was very stiff when trying to manually adjust so it appears something is gummed inside the headlamp stopping the beam unit from tilting up and down. Will have to remove the whole headlamp assembly to look inside and try and find the cause.

enuff_zed · Post by **enuff_zed** » Mon Sep 20, 2021 11:42 am

portculisz4 wrote: ↑Mon Sep 20, 2021 11:06 am Thanks for your response. Have removed plastic under wing cover and also headlamp cover revealing the small motor inside the headlamp unit. This does appear to work when operating the headlamp thumbwheel but the headlamp assembly does not move. There appear to be two beam adjusters on unit itself one fed but a flexy stainless cable (on the outside of the unit), this was very stiff when trying to manually adjust so it appears something is gummed inside the headlamp stopping the beam unit from tilting up and down. Will have to remove the whole headlamp assembly to look inside and try and find the cause.

Well that's a pain!
Hopefully nothing is broken and it'll just take time and a good clean up.
Just hope that the seized headlight hasn't caused anything to shear or strip inside the motor!
Often little motors like that will have a weak link built in so that if the thing they're moving does get stuck then the motor can continue to spin and doesn't overheat.

portculisz4 · Post by **portculisz4** » Mon Sep 20, 2021 11:52 am

Won't really know until I can take a more intimate look inside the lamp unit although there is a small issue in trying to remove electrical connectors. The cable to the headlamp assembly is a large single cable that forks into two just before the connectors, One is quite substantial and I guess is the main power for both beams, the other is quite slender and I guess is the power for the tilt motor. Its the small one I am having difficulty removing, do you know if there is a special clip to this connector

enuff_zed · Post by **enuff_zed** » Mon Sep 20, 2021 11:56 am

portculisz4 wrote: ↑Mon Sep 20, 2021 11:52 am Won't really know until I can take a more intimate look inside the lamp unit although there is a small issue in trying to remove electrical connectors. The cable to the headlamp assembly is a large single cable that forks into two just before the connectors, One is quite substantial and I guess is the main power for both beams, the other is quite slender and I guess is the power for the tilt motor. Its the small one I am having difficulty removing, do you know if there is a special clip to this connector

Sorry, I don't. Not been in there yet!

portculisz4 · Post by **portculisz4** » Mon Sep 20, 2021 3:42 pm

The motor control is the small 4-wire connector. I have removed head lamp unit and ascertained how the level adjustment works - it is driven from a small motor that winds a plastic piston in & out tilting the whole lamp assembly. The motor is easy to disassemble and consists of two identical stator coils with a pair of wires from each going to the socket in the headlamp casing. Continuity of the coils was good (9 ohms each) and there was no issue with the mechanical operation of the rotor and the screw mechanism which winds the piston in and out. I now believe the problem is at the thumb wheel end and need to remove the mini panel that holds the thumb wheel control.

So my next qestion - is this mini panel straight forward to remove, do I need to remove any panels under the dash first ?????

Sidewaze Samm · Post by **Sidewaze Samm** » Tue Sep 21, 2021 1:08 pm

portculisz4 wrote: ↑Mon Sep 20, 2021 3:42 pm So my next qestion - is this mini panel straight forward to remove, do I need to remove any panels under the dash first ?????

If you mean removing the trim panel around the lightswitch (LCM) to provide access to the LCM, then it's simple:
Preferably using a trim removal tool (or large screwdriver with tape around the blade) lever up the lower edges of the trim piece. I think starting at the lower left corner gives the best result (but it might be the lower right...). Either way, being careful will result in the panel being popped off. You then have two screws to release the LCM, which can then be pulled out of the dash (a little awkward and will require some fiddling and tilting) until it is far enough out that the cable connection can be released.

portculisz4 · Post by **portculisz4** » Thu Sep 23, 2021 12:43 pm

Problem at last solved - worked out problem could only be in the headlamp unit (stepper motor), the LCM or the cable harness. Stepper motor easy to check and OK, tried the wiring harness next. Managed to get at the socket connectors at each end and started testing for continuity from the 4-pin socket at the headlamp end, it was trial & error by probing each of the 48 sockets at the LCM plug end. Only found 3 wires with continuity could not find a forth so assumed this was the issue, an open circuit, so the fix was to create an replacement link between the two sockets to replace the open wire. First major problem was getting through the 40 plus wires on the back of the 48-socket plug to find the bad wire so scrapped this idea. Removed circuit board from LCM and it was easy to trace the circuits going to the 4-pins on the circuit board substrate and identify the pin relating to the open wire connection. From here I soldered short length of wire to the circuit board and took this out through the LCM casing. Next problem was finding a way to feed 2M length of wire through the bulk head to the engine compartment but managed to pierce the large rubber gasket that the main wiring harness passes through and force a single wire through it. Just a matter of passing along headlight harness and breaking the connection at the 4-pin socket end and attaching the new replacement wire, Problem solved, headlight angle adjustment now working. My guess is that the Garage would have by default replaced the headlamp unit and then the LCM before realising that didn't solve the problem. They would then have as a last measure replaced the whole wiring harness (how much labour cost is that ??) giving me a total bill of several hundred pounds for only a faulty wire connection. Always worth having a go yourself first.

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