As stated in the title, one of the two instrument cluster MFD bulb positions won't light up. Any of the same size bulbs work in all the other four positions. All the bulbs work. They are not LED's but standard, quality replacements (Flosser). The bulb housings are original. I have tried:
*Swapping other bulbs assy's into the position
*cleaning the contacts on the bulb housings
*cleaning the contact 'track' on the circuit board.
Thinking the bulb housing wasn't making good contact, I even tried a conductive silver paint, put on with a syringe. Let it dry for three days. No dice. Used a bit of 430 grit sandpaper, to smooth out the conductive strip of paint. still no function. Used a nick sander for the same purpose. Not a chance.

There are two contact 'tracks'. With no bulb installed, I found 12.24 volts on one side and .11 volts on the other. I have pulled the cluster apart to inspect it related to this problem before this, but also did it again tonight. This time I carefully worked the MFD unit off the board to see the other side of the PCB where the two bulbs are hidden by it. Looks fantastic under there.

Has anyone else run into this particular problem?

I find myself wishing for a substitute bulb base, one that maybe has a slightly different contact track, to test this with. That's about all I got. Any suggestions out there? Thanks in advance for any help or guidance.

If you can find a small 16 ohm resistor, just tack it in there being sure it isn't shorting to another track. It doesn't have to be an SMD

Here's some White LED wedge lights that I have for my 850 instrument cluster.
http://www.dx.com/s/81588?categoryId=1353
There's four of them and I have not tried them yet. They offer some benefits, less current draw, not prone to blowing out up to 16 Volts, way more immune to shock and vibration, and long life, which is always nice in the instrument cluster. LEDs make filament bulbs obsolete mostly, and they might be less expensive.

They come in many other colors.
This is the page for T10 wedge lamps in blue

http://www.dx.com/s/t10+blue?categoryId=1353

Maybe the Blue LEDs will do the trick for you?

There's two types of sockets for the T10 wedge: one has the bare wires bent over a plastic base, and that arrangement didn't like the red door markers socket in the 850. The more reliable T10 base uses a PC board and works fine.

There's quite a selection there, be careful that you don't over do it since a
5W LED will most likely be way too bright maybe this one might be suitable?
They're cheap enough to give em a shot.

http://www.dx.com/p/sencart-t10-1-25w-70lm-5-smd-5050-led-ice-blue-car-backup-light-12-16v-2-pcs-181993
You might find the 1.25W too bright as well?

The LEDs are polarized so you can install them backwards.
I don't know if they are dimmable.

Post back with any good results.

Bill

Thanks Bill, I will post up any results. I suspected a more common resistor might do the trick. I have a local Mom & Pop electronics store that will most definitely have what I need. Hell, they have what I don't know I need sometimes. Unless I hear otherwise, I am thinking of leaving the bad one in place and just tacking trimmed wires in on top. The bulb contact is right there to clip a small aluminum heatsink onto so I shouldn't cook anything else while I'm working there.

I had bought a few LEDs and dabbled at replacing the entire clusters worth plus switch illumination. On paper the benefits are there to be sure. There is such a wide variety of color hue, brightness, diffusion, physical shapes and sizes out there and it's mostly subjectively described by sellers if at all. Too much trial and error for me to get it right. Basically I got to point where it's enough already and I'm out of time to mess around with it anymore. I'm left with a very satisfactory COB LED in the trunk with new flanking 6 LED boards in mk4 VW Jetta housings popped into new cut outs in the trunk lining. That mod worked out very well. I also left in the license plate lamps and for now, floor/step lamps. I may revisit the tail/brake lamps, turn signals and running lamps later. When I can find good replacements that won't set off the bulb out sensors. For now they work and I'm good with just that.

Look at what's on EBAY:
http://www.ebay.com/itm/99-00-VOLVO-V70R-Speedometer-Instrument-Cluster-with-Blue-Face-223-793-Miles-/181722288083?fits=Make%3AVolvo&hash=item2a4f7e0fd3&vxp=mtr

All you need to do is swap mother boards, so you have your mileage...
--
My back feels better when I sit in a Volvo seat

I saw that cluster, thanks. Hopefully there will still be a few out there when I get a bit more cash scraped up. Other priorities are taking precedent right now.

Well, I picked up a 1/4 watt 16ohm resistor yesterday and tested it by touching the contacts with a known good bulb and she worked. I soldered it in tonight, right over that dead SMD and hopefully it still works. There is a little blue fuzz on it where I wiped it off with a rag.

I tested it late last night and it seems to work well. Time will tell I suppose. It seemed very solidly mounted once it was on there so I think the only problems that might crop up would be related to the actual resistor spec, since I had to guess at some of the specifics. I will report if it fails in the future.

Hi Duke

OK on your luck with LEDs, Not all are involved with the bulb out sensors.
Low Beams, Brake and tail lights, leaving Courtesy lights mostly ready for
LEDs. Here is what works great in the license plate lights
http://www.dx.com/s/273523

I found the interior and trunk LEDs to be well worth the trouble, since the light is so much better. I changed out most running lights in an effort to reduce
the current flow enough to see some increase in MPG by reducing the alternator
load, but I can't prove there's a payoff like that.

Bill

Well I made some headway last night with this and , in trying to add it my original post, managed to create new ones.

The bad socket has no continuity between the two contacts while the rest do have it. In following the circuit pathway, I discovered an SMD resistor that does not have continuity either. The mirror circuits' SMD resistor (for the other MFD display bulb) does. Pic below:

From what I can tell, the "160" marking means 16 ohm. It certainly looks as if I'm going to be replacing that resistor if I want that lit up at night anyway. The dash is out of this car but I may still wait. I was interested in finding blue face gauges which means I will likely be buying a used cluster anyway. Might be best to have that around before I try my hand at replacing the SMD resistor.

At the very least, I know much more than I did before and that there isn't anything wrong with my sockets, bulbs or contacts.