Battery on way out?

thatfatbloke · August 27, 2016

Just done a 600 mile round trip to Somerset and noticed something I hadn't seen before. On leaving for home on a foggy Thursday morning I used the headlights for the first time since owning the car. Every now and then the dash lights,clock and outside temperature gauge would flicker. Just for a split second. I suppose I noticed it around 10/12 times in the two hours I had the lights on. Was it on here I read that it could be a sign of a Battery starting to die,or was it on the M**c***s forum?.Ta.

Jake430 · August 27, 2016

Is your car fitted with an automatic light sensor

thatfatbloke · August 27, 2016

2 minutes ago, Jake430 said:

Is your car fitted with an automatic light sensor

No.

thatfatbloke · August 27, 2016

Before anyone suggests it,I will of course check the Battery connections when SWMBO deigns to let me have my car back!. Battery was disconnected a couple of weeks ago for cambelt replacement.

Malc · August 27, 2016

....... never noticed it happening on mine over the last 5 years and now at @187k miles

wonder if it's something to do with the fog lights being in the same cluster as the headlamp .... did you turn the fog lamps on too ?

Malc

Titch LS · August 28, 2016

John, my mk4 occasionally does exactly the same flickering that you describe. It has nothing to do with a defective Battery but the light sensor Jake 430 was on about. It happens mostly at dusk or when you emerge from a tunnel or pass through a shaded area of road. Perfectly normal.

thatfatbloke · August 29, 2016

Strangely enough I did tend to notice it more when going under a bridge,but put it down to coincidence. I didn't realise I had an automatic light sensor,there is certainly nothing like my wife's M**c which has a position on the light switch for 'auto' lights. What is the job of this light sensor then please?. And no Malcolm I didn't use the fog lights.

Titch LS · August 29, 2016

The light sensor is the little button-like thing at the base of the windscreen. It is for use when the headlight stalk is turned to "Auto". I believe the sensitivity can be adjusted by the dealership. I've never used the auto setting myself, but now you've brought it up, I might just try it!

Verbout · August 29, 2016

6 hours ago, Titch LS said:

The light sensor is the little button-like thing at the base of the windscreen. It is for use when the headlight stalk is turned to "Auto". I believe the sensitivity can be adjusted by the dealership. I've never used the auto setting myself, but now you've brought it up, I might just try it!

I thought that was the air con temperature sensor.

sorcerer · August 29, 2016

As others have said it's most likely the light sensor but one thing I can say is that it's not a sign of a defective Battery. Once the car fires up and the engine is running, all onboard electrics are fed by the alternator, not the Battery. If there's enough 'spare' power (which there obviously should be and usually is) then the alternator will charge the Battery, but the Battery effectively becomes redundant once the engine and alternator are running.

Titch LS · August 30, 2016

Gary, the aircon temperature sensor is located just behind the dash near the steering wheel. It looks like a small 1" square grill in the plastic. Not very noticeable.

thatfatbloke · August 30, 2016

There is certainly no light sensor on my dash,nor is there an option for 'auto lights'. Perhaps only MK4's upwards had it. I'll take a pic later as I've got to go and change the bonnet struts anyway. There is a strange round 'thing' by the gear stick which I'll also take a pic of.

ambermarine · August 30, 2016

John

There is a light sensor in your Model the LS400 range from Mark 1-4 had them and they dimmed the dashboard lights when driving through tunnels and during dawn and dusk .

The sensor is located at the right of the base of the windscreen.

The Mark 4s were the only model to have the light sensor linked to the headlights.

thatfatbloke · August 30, 2016

1 hour ago, thatfatbloke said:

There is certainly no light sensor on my dash,nor is there an option for 'auto lights'. Perhaps only MK4's upwards had it. I'll take a pic later as I've got to go and change the bonnet struts anyway. There is a strange round 'thing' by the gear stick which I'll also take a pic of.

I may stand to be corrected here. I was assuming the sensor would be in the middle of the dash. I've just taken a pic of one I found on the nearside (the black domed one,fourth pic) and there's another one in front of the driver (third pic). Still no option on the light switch for auto though. I know the thing by the gear stick is irrelevant,but don't have a clue what it is.

thatfatbloke · August 30, 2016

1 hour ago, ambermarine said:

John

There is a light sensor in your Model the LS400 range from Mark 1-4 had them and they dimmed the dashboard lights when driving through tunnels and during dawn and dusk .

The sensor is located at the right of the base of the windscreen.

The Mark 4s were the only model to have the light sensor linked to the headlights.

Ah, I understand now ambermarine. Was assuming auto lights meant headlights as opposed to dash lights. Thanks.

thatfatbloke · August 30, 2016

My theory about the round thing is as follows. When the LPG system was fitted in 2008,the installers put the gauge in that position,the owner didn't like it there and had it moved to where it is now,behind the lights/indicator stalk (where you can't see it when driving!). It doesn't rotate or pull or push,so assume it was the nearest thing to hand to cover up the hole that was left behind when the gauge was moved.

39buss · August 30, 2016

It may be a sensor for the remote opening of the garage door. You could easily pop that gear lever cover off to see if there's any wiring running from underneath.