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Author Topic: Headlight query  (Read 811 times)
Drbagheera
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Posts: 52


« on: January 14, 2017, 01:16:05 pm »

Hello everyone

My murena has a headlight issue. The lights come up whenever the engine is running regardless of the headlight switch position.

There has been some modification to the loom unhappily, and a separate switch operates the sidelights, but the headlight stalk twist switch still works main and dipped beam.
I have confirmed that the wiring to the solenoid is live from ignition rather than from the switch which I think is incorrect?
The plunger can manually switch the vacuum supply to either side of the diaphragm controlling the lifting of the lights ok. 

So should the power supply to the solenoid be switchable or do I need to play around with vaccuum plunger and the metal strip that retains it as I have read elsewhere?
Thanks
Ian
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suffolkpete
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Posts: 453



« Reply #1 on: January 14, 2017, 01:39:46 pm »

If there is a supply from the ignition to the solenoid then it will cause the headlights to come up whenever the ignition is on.  It should only come on when the either the main or dipped beams are illuminated.  It is fed from connector 4 on the green connector on the fuse panel on the left hand side of the front compartment.  Get the electrics right before considering the solenoid itself.
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roy4matra
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Posts: 871



« Reply #2 on: January 14, 2017, 11:33:49 pm »

Hello everyone

My murena has a headlight issue. The lights come up whenever the engine is running regardless of the headlight switch position.

There has been some modification to the loom unhappily, and a separate switch operates the sidelights, but the headlight stalk twist switch still works main and dipped beam.
I have confirmed that the wiring to the solenoid is live from ignition rather than from the switch which I think is incorrect?
The plunger can manually switch the vacuum supply to either side of the diaphragm controlling the lifting of the lights ok.  

So should the power supply to the solenoid be switchable or do I need to play around with vaccuum plunger and the metal strip that retains it as I have read elsewhere?
Thanks
Ian

The fact that the solenoid is being fed from the ignition, and the head light pods are lifting, and going down again when the ignition is off, shows that the solenoid and double acting head lamp servo are operating correctly and there is nothing wrong with that part of the system.  The fault will probably be on the circuit board and since someone didn't understand it or know how to repair it, they have altered the wiring and given the solenoid that direct ignition feed.

The circuit board contains three diodes and it is through these that the solenoid should be fed.  The diodes get their feed from the same circuits as the ones operating the dip and main beam relays, and they are operated from the stalk switch.  Since you have confirmed that the headlamps do work, it means that one or more of the diodes or their circuits have failed.  Probably the diode(s).

I have seen this before where both dip and main beam would come on together because a diode had failed such that it was allowing a feed in both directions, the consequence of which meant that there was a cross feed joining the dip and main beam circuits.  If it happened on your board and the person did not understand this, or how to put it right, they have disconnected the solenoid feed from the board and simply wired it to the ignition instead, which means that the pods will lift anytime the ignition is switched on.

It is possible the feed between the board and the solenoid has failed, rather than a diode, but either way, hopefully you can now diagnose the problem and put it right correctly.

Roy
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Drbagheera
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Posts: 52


« Reply #3 on: January 14, 2017, 11:43:41 pm »

Many thanks for the advice above. I will investigate further, but it would be better to go back to stock operation I think.
One additional point however, was that with ignition off, the headlights don't fall unless I disconnect the vacuum hose feed, I.e. The supply to the solenoid is stopped but the vacuum feed to pull the lights down fails to switch over. Would thus then be another fault?
Cheers
Ian
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roy4matra
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Posts: 871



« Reply #4 on: January 15, 2017, 12:59:56 am »

Many thanks for the advice above. I will investigate further, but it would be better to go back to stock operation I think.
One additional point however, was that with ignition off, the headlights don't fall unless I disconnect the vacuum hose feed, I.e. The supply to the solenoid is stopped but the vacuum feed to pull the lights down fails to switch over. Would thus then be another fault?
Cheers
Ian

Hello Ian,

Your answer here tells me you don't really understand this system properly.  You say you think 'it would be better to go back to stock operation' and my previous answer had told you how it was designed to work so you could fix it to do that.  You didn't originally state that the pods were not being pulled down, and pulling the vacuum supply hose off the solenoid should *not* make them drop as they need to be *pulled* down.

Your statement above suggests they are dropping after the vacuum is removed, and that should not happen if the linkage is set up properly.  The head lamp pod linkage is designed to go 'over-centre' so it locks in the up position, and neither weight nor aerodynamic forces should cause them to drop if the vacuum is lost.  So if all vacuum is lost and you pull the pods up with the emergency cable, they will stay up.  To get them down when there is no vacuum, you need to pull the linkage back past the over-centre position that locks them in the up position so they can then be pushed fully down.  If the linkage does not go over-centre and lock, then pulling them up with the emergency cable will result in them dropping again, which is obviously no good!  To manually release the lock position you have to go underneath the front and push the bar connecting both pods, backwards.

For the system to function from the stalk as originally designed, the stalk switch when switched to either the dip or main beam positions, sends a 12v feed to the circuit board which feeds both the relay for the relevant head lights (dip or main) and also supplies a feed to the diodes which sends a signal to the vacuum solenoid.  This solenoid moves the internal valves to direct the vacuum from the reservoir to the lift side of the dual acting servo, and the light pods are lifted.  The relay will have already switched the lamps on.

If you now change the stalk to the other beam setting, the first relay will switch off and the other relay will switch on and the beam will change (either from dip to main or main to dip depending on which was already on).  Since both settings send a signal to the diodes the pods will remain up between changes.

If you now switch the headlamps off and go back to side lights or lights off altogether, the voltage signal to both relays and diodes is cut off.  With no feed to the lift/lower solenoid, the spring should push the valves back to the off position and the vacuum from the reservoir is now directed to the down side of the dual acting servo, the linkage is pulled out of the lock position and the pods are pulled down.

So you need vacuum to pull the pods up and vacuum to pull them down.  If yours are not being pulled down, you need to determine if this is the valve not springing back into the down position; or there is a leak and/or there is no vacuum to pull them down for some reason; or the servo is not moving in the correct direction to pull them down as it is stuck, or there is something wrong with the linkage...  etc.  Since we are not there we cannot see what is happening and therefore what part(s) are faulty, but if you understand exactly how it should function, you should be able to determine which part of the system is not functioning as intended.

One final point is that the bonnet release should be inhibited when the head lamps are up.  This is because the gap between the pods when up is narrower than the bonnet between them and if the bonnet was lifted it would hit the edges of the pods and damage would result.  So if the interlock is not working and you *can* release the bonnet with the head lights up, please note you must not lift the bonnet until the head lights are lowered.

Roy
« Last Edit: January 15, 2017, 01:08:04 am by roy4matra » Logged

Drbagheera
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Posts: 52


« Reply #5 on: January 15, 2017, 07:45:11 am »

Thanks a Roy. I understood the system, I just didn't explain the situation well.
Spent an hour on the problem today and fixed it by-

Hardwiring a failed track in the fuse board
Adjusting the vacuum plunger metal end cap

Thanks everyone
Ian
« Last Edit: January 15, 2017, 03:28:33 pm by Drbagheera » Logged
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