2004 XC70 Headlights always on

altalake · Post by **altalake** » 01 Apr 2021, 02:24

This XC70 has Xenon headlamps and the always-on lights (daylight, lights turned to off) are supposed to be the daytime running lights, not the actual headlights. The DRLs never turn on. The Xenons are always on. The daylight sensor is supposed to be one and the same as the "alarm on" LED on the dash, yes? Could this be a relay on the CEM or elsewhere? If this car had halogen headlights, this would be normal, but not supposed to work like this with Xenons.

Post by **- Pete -** » 01 Apr 2021, 08:37

This is an election in ViDA. The previous owner either had it set that way or received it that way and didn’t notice/care/know that it could be altered. It’s not a difficult task by any means, but you need ViDA/DiCE to alter lighting configuration.

The only time you should need to think about relays is if you are adding functions to a car that previously didn’t have them, such as adding fog lights to a car that didn’t come with them. As far as I know, all P2 XC70’s came with factory installed fogs.

Post by **June** » 01 Apr 2021, 12:49

No something is wrong! My 1st S80 T6 had Xenon optional lights. The Xenon should automatically come on at dark via the sensor on dash. Otherwise it reverts to standard bulb type Daytime Running Lights. I imagine some lighting module is acting up. Have you had the car checked? June

altalake · Post by **altalake** » 21 Apr 2021, 23:10

Thanks for your replies. Apparently this is not a VIDA option problem because sometimes the running lights come on when they're supposed to - but usually not even in bright sunlight. The daylight sensor is part of the alarm-active LED on the dash I believe. No errors relating to lighting show up on the cheapo aftermarket VIDA.

Post by **kcodyjr** » 23 Apr 2021, 10:13

Just a WAG, but could your daylight sensor be on the fritz?

Post by **matthew1** » 23 Apr 2021, 10:53

kcodyjr wrote: ↑23 Apr 2021, 10:13 Just a WAG, but could your daylight sensor be on the fritz?

This is bang-on the bullseye for the Check Easy Stuff First ethos... the simple -> complex diagnostic workflow I, for one, adhere to, and champion.

Post by **abscate** » 24 Apr 2021, 04:13

Canada is a different market , with full time DRL mandatory, so cars made for this market might not give you the options in VIDA that Southern British Colonies get.

It’s a conspiracy to sell auto light bulbs and contaminate our precious bodily fluids, Mandrake.

altalake · Post by **altalake** » 25 Apr 2021, 22:28

I fully concur that checking the easy stuff first is the most sensible plan. Re: that daylight sensor - It is what/where exactly? Is it the very same LED on the dash that flashes to show the alarm is on? If so, it flashes just fine - which does not mean it's working as a sensor just fine. If not, where might it be?
And that sensor is connected to a circuit which is where? Anybody know? I have checked several wiring diagrams and haven't found it. Likely the CEL but maybe not.
And last of the simple things (I think), that either/or circuit (DRL or Headlights) probably goes to a relay. Possibly this one: https://www.carid.com/standard/intermot ... l=13834578
I haven't found a relay described for this function in the wiring diagrams. I lean towards this being the problem because it's intermittent - something an electromechanical device like a relay could exhibit. And there are no associated fault codes. The lights behaved just as they were supposed to when the car was with my mechanic but only rarely before or since then.
Yes, this car is Canadian issue with either DRL or headlights on and I'm not trying to defeat or modify that - just trying to not have the $100 xenon bulbs lit up 100% of the time.

EngineeringBloke · Post by **EngineeringBloke** » 28 Apr 2021, 18:57

A LED is a light emitting diode (like a bulb) - it cannot act as a sensor.

I found a discussion of the location of the daylight sensor. It seems to have been located on the climate control panel at one time: https://www.swedespeed.com/threads/loca ... sor.27820/

altalake · Post by **altalake** » 30 Apr 2021, 20:57

Thanks so much. It turns out the sensor is, in fact, a 1mm x 2mm spot at the bottom of the Climate Control Module. Odd place for it, to be sure. It might just need the sludge cleaned out for it to work more reliably.
FYI, LEDs can be and are used as light sensing devices as well and it looks like the newer Volvos do make use of the alarm LED as a sunlight sensor.
Thanks again.

https://www.wikingerparts.de/en/shop/vo ... r-31288760