Partial intermittent dashboard display lights failure.

[rogereld]

Usually after the car has been parked unused for a week or more, I get failure of some of the interior dashboard backlights. They sometimes come back on after a period of driving. Mostly the rear illumination of the speedo/rev counter dials, the radio and the headlight on/off switch. Climate control backlights work OK. Sometimes I get very dim illumination even when the dimmer is set to max. Sometimes the headlight switch remains on daylight running and will not switch to sidelights or dip/main beam, and fog lights will not operate.

Any suggestions where I should start to look for the source of the fault?

[shezzav70]

Perhaps start with checking any relevant fuse(s) & connections there?
If not, remove the cluster & check connections there? Perhaps a connection is loose? Maybe wiggle the connector around with lights on to see if it gets better/worse...
https://www.youtube.com/watch?v=ZvSXIM-RWn8
Looks easier than I was expecting....
Not sure if you'd have to disconnect battery before removing plug to cluster but might be worth doing to be safe.
Good luck

[Simmy]

always disconnect the battery before unplugging components to avoid any chance of triggering warning lights which may require vida or similar to reset

[rogereld]

The problem with my headlight switch module has now re appeared.
Very dim, or no backlight on both the radio and the text displays on the dashboard. Daylight running lights work but the switch for sidelights and main headlights for night time driving do nothing, so I cannot switch full beam on at night. Rear and front foglight, beam adjust and dash dimmer switches do not work. Sometimes after driving for a while the problem disappears and all controls work as normal.
This has not been a problem during warm weather and mostly daylight driving. I suspect cold and/or damp may be causing problems.
My own internet research has found a couple of similar reports and hints that failing solder joints on the headlight control switch module may be the source of the problem.
I have found a youtube video of someone soldering the circuit board but there is no commentary to explain. I have a soldering iron but the microscopic joints are beyond my capability so I am looking for a replacement.
If anyone is breaking a 2001-2007 V70 and has a working light switch module available that matches this part number please let me know. The part number for my 2001 V70 is 9441233.

[rogereld]

All the faults have been fixed by replacing the Light switch control module.

Instrument dimmer and headlight level adjuster works. Sidelight and headlight full beam work. Front and rear fog lights work.

For anyone with a similar problem in future, The circuit board inside the V70 lighting control module is the same as the one used in some XC90's. I found a cheap used switch module with part number 8685452. The original V70 part number is 9441233.

The XC90 switches were a slightly different colour, so I removed the XC90 circuit board and fitted it in to the V70 module.

[volvo2]

Originally Posted by rogereld

Usually after the car has been parked unused for a week or more, I get failure of some of the interior dashboard backlights. They sometimes come back on after a period of driving. Mostly the rear illumination of the speedo/rev counter dials, the radio and the headlight on/off switch. Climate control backlights work OK. Sometimes I get very dim illumination even when the dimmer is set to max. Sometimes the headlight switch remains on daylight running and will not switch to sidelights or dip/main beam, and fog lights will not operate.

Any suggestions where I should start to look for the source of the fault?

I have almost exactly the same problem, except my headlight switch is not affected and operates as normal. I guess as you were able to replace with a secondhand unit, these are not coded to the car in some way? By the way, my local Volvo dealership now want £186 just to plug the diagnostic test in!

[rogereld]

The light switch control module is not coded to the car and was fairly easy to replace with a used item from another car. Changing the climate control module may be less straightforward. I had some strange intermittent problems with the dashboard and climate control illumination even when the headlight switch module appeared to be working correctly. Cold and damp conditions sometimes made the problems worse or more evident. I first noticed faults during February/March 2023 and it took me almost a year to fix because the faults were not evident when the climate warmed in Spring. Also as I was doing a lot less driving in the dark I didn't notice the dim backlights until November. I think corrosion or failure of some components or solder joints in the light switch module was causing problems in my case.

If your problems appear in the illumination of the radio, climate controls and also the speedo/rev counter etc it is most likely to be a fault in the lighting control switch circuit board.

[volvo2]

Yes, that is the problem I have in a nutshell. I'll see how much a new unit is from Volvo and if that is a crazy price, look for a used one. I first have to find a way to clear the "SRS-AIRBAG SERVICE URGENT" error message I now have. I'm pretty sure this is unrelated and simply caused by me foolishly removing fuse number 24 (to see if that was the problem) and starting the car.

[volvo2]

Turns out that the iCarsoft i906 diagnostic reader was able to both read and erase my SRS error message. I’m very impressed with this device – it cost me less than one diagnostic visit to the dealer. Based on this excellent video (https://www.youtube.com/watch?v=gTSZX0yw8RQ&t=134s) I was also able to find the cracked solder joint and repair it. Hopefully the issue of intermittent dim / no instrument lights is now solved. In the attached image I highlight the surface mount component with the cracked solder joint. I was able to see the crack with a 10x magnifying glass.