Sudden loss of main beam

[924nutter]

LIke it says. Had the car in for code readout for check engine warning, and had the airflow sensor changed for a test one to try for a week. Have to say the engine idles better not sometimes 1200 rpm just a steady 900. Unfortunately on the way home went for main beam and got nothing, headlight remained illuminated in low beam. Headlight flasher works. Can the high beam be accidentally disabled by the diagnostic lap top. One thing I notice is that if the ignition is turned off with the lights on, then turned back on the reflectors in the Xenon lamps seem to hunt for position and I wondered if something has jammed. This is happening on both headlights

 

[Richard_Hamilton]

The lights are all hard wired, so the diagnostics wouldn't affect them. Only the level control has a control module.

Headlight switch. Very common, and there is a DIY in the Technical Articles section.

 

[hopeydaze]

I had the same problem - replaced lightswitch (well, Northway did it or me) and problem solved.

 

[924nutter]

Yes thanks guys. I am having trouble getting my head around the switch being responsible for this fault. I would love to study the wiring diagram, but you can't both be wrong. My basic concept of headlight switches is power in power out to a change over relay. this looks like about a 3/4 hour job to me but I might try the box spanner in the tool kit or see if some of my double depth sockets will undo the retaining nut. Just typical as it is going to cost me £250 for the air-flow sensor. and now £85 for the switch.

 

[Richard_Hamilton]

ORIGINAL: 924nutter
.......My basic concept of headlight switches is power in power out to a change over relay. .........

Therein lies the problem - no relays. The full power goes through the light switch.

 

[minny]

The retaining nut is not tight. I undid mine with angled long nose pliers.

 

[924nutter]

ORIGINAL: Richard Hamilton

ORIGINAL: 924nutter
.......My basic concept of headlight switches is power in power out to a change over relay. .........

Therein lies the problem - no relays. The full power goes through the light switch.

Yes that was a stupid thing to say as even on my 924 the full current went through the switch which is why they used to melt with monotonous regualrity. So what happens? Even if the full power goes through the switch the contacts would be rated for it, and on the 944 the contacts on the column switch switch the load. Call me thick but why would you have two outputs from the switch, one for low and one for high when you can just send one output to the column switch and let it switch the load. Maybe it has something to do with the xenons. Don't get me wrong, I am not challenging the informed wisdom, I have already odered a switch, and actually a new switch and two speed fan switch for the 944T work out cheaper from OPC than from a well known independent when you factor in p&p.

 

[924nutter]

Now here's the thing, I now have a sudden re-instatment of main beam after driviing the car for about 60 miles. tried a few on/off cyles and many dip/main cycles 'til the locals thought I was around the twist. Apparently in good working order; of course OPC already have my new switch reay to be collected.

 

[Richard_Hamilton]

I think "apparently" is the key word there. They do become intermittent, so I would change it anyway. You don't want a failure at speed..........

 

[924nutter]

Yes good thoughts there Richard, I shudder to think of the consequenses should I experience a loss of low beam as well.