My mk2  Octavia vrs (hatchback) reported a bulb out... I located this to be one of the small w5w bulbs, which I replaced. All was good for about 20 minutes then the dash light came on again with the same bad bulb, I then replaced the other one fiddled with the two larger 380/p21 bulbs and turned the ignition off then on again all was good so I put it all back together again and went to check and it had stopped working again. Any ideas please guys.

Did you turn off the headlight switch and then cycle the ignition?

 

I had similar problems when replacing the front running light and recall you had to "reset" the brainbox by turning off the switch.

Try another bulb in each, one of them is likely on its way out. The less likely option is that for some reason the MFD is sensing it wrong. If that is the case, you can always code it out using VCDS, but that has the con of not telling you when you have a light out of course.

2 hours ago, marfrohun said:

Try another bulb in each, one of them is likely on its way out. The less likely option is that for some reason the MFD is sensing it wrong. If that is the case, you can always code it out using VCDS, but that has the con of not telling you when you have a light out of course.

 

The MFD doesn't sense if the bulbs are working. The BCM or CECM both powers the bulbs and does the bulb checks. If it decides one or more bulbs are out of spec, it'll send a message over CAN-bus to the instrument cluster which will display the warning.

 

As Brad mentioned, once a bulb has been detected as at fault, the car will sometimes refuse to power it to protect itself. An ignition cycle should normally be enough to resolve this.

 

Otherwise, it's worth checking all the external bulbs are working and making good contact with their bulb holders. If the fault remains, it's worth using VCDS or similar to find our exactly why the car is unhappy.

1 minute ago, langers2k said:

 

The MFD doesn't sense if the bulbs are working. The BCM or CECM both powers the bulbs and does the bulb checks. If it decides one or more bulbs are out of spec, it'll send a message over CAN-bus to the instrument cluster which will display the warning.

 

As Brad mentioned, once a bulb has been detected as at fault, the car will sometimes refuse to power it to protect itself. An ignition cycle should normally be enough to resolve this.

 

Otherwise, it's worth checking all the external bulbs are working and making good contact with their bulb holders. If the fault remains, it's worth using VCDS or similar to find our exactly why the car is unhappy.

My apologies, I misspoke. Did not mean the MFD. 

I've replaced both bulbs of the same type and cycled the ignition/lights and it worked for a while then stopped again... Will plug in vcds and see what the code is.

You're fitting the wrong bulbs. Always replace like-for-like.

 

The MkII Octavia is very fussy over it's bulbs.

 

You need W3W, not W5W.

 

I had a similar issue, the W5W doesn't look obviously brighter, but they blackened very quickly and were regularly flagging as blown. After realising my mistake and sourcing some W3W bulbs, they were fine...

 

Ok... I will try w3w if I can source them... Just had new front tyres and the mechanic said that they are usually 3 watt but he thinks that it's a bad earth possibly where the cabling comes through the boot lid but I can't find anything wrong there so will try different bulbs