The lamp to illuminate the temperature display is plugged into the top of the module and can be accessed from the back.

Take out the lower panel, knee cushion, and the relay bracket attached at the left side of the steering column to get access to the module. There will still not be adequate room to get enough grip on the lamp holder to turn it. I used my small 8mm combination wrench to give it a 1/4 turn CCW so with two fingers I could lift it out of the hole. (Get a new lamp with holder from the dealer and check the wrench size.) With two fingers drop the new bulb in the hole and use the wrench to give it the 1/4 turn back in.

I had to get part of the 1/4 turn with the wrench one way and then turn it over to get the rest of the turn.

The relay bracket is held with a single bolt on the lower end and has a tab and slot arrangement to hold the upper end. Check it out as you pul it down so you can get it back in the correct location on reassembly.

Hope this helps.
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'96 965 with 16' wheels at 119K. Had '85 745 Turbo Diesel for 200K.

I think JD was thinking of the earlier ambient temp guages. For the LCD gauges in the '95 900, the bulb is on top of the ambient temp gauge. The bulb has a blue base with a square end and inserts with a quarter turn into the top of the unit. I don't think you can find it anywhere except Volvo. Sorry, I can't find my receipt with the correct part number. The bulb can be a PITA to get at and replace as there is only a small space above it. The best way is to remove the instrument cluster so you can see what you're doing.

As for the switch bulbs, these have an integral black plastic bayonnet base. The switch cluster bulbs are p/n 1363149 and you won't want to be buying a box full as these are quite expensive (like around $10 each) and of course only available from Volvo. I believe there was a RWD post recently on re-building these bases using LEDs and there is also the option of getting the older style bayonnet bulb bases with the replaceable bulb out of a 740 and splicing the wires. Some bulbs are in the switches and some are inserted in a light tube at the top of the switch clusters. If you try to yank the switch clusters out you can damage the dash unless you press in a spring clip on the outer back side of the cluster and swing the switch cluster out. If you remove the instrument cluster to do the ambient temp bulb then they should be relatively easy to locate and replace without removing the switch clusters.

Read the FAQ and search the RWD forum for previous posts on these topics such as this and this thread.
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Dave -not to be confused with a real expert

The ambient temp gauge has a bulb inserted into the rear of the gauge. Check your owners manual for the size; it should be listed. It sits in a plastic sleeve and can be twisted and pulled out.
Lighting for the buttons is via replaceable peanut lamps in the rear of each. They are 1.2W I believe, and are availale through Volvo and other sources. Buy a box of them, and replace all of the bulbs, as they burn out fairly regularly. If you pop the switches out they are not too bad to switch, although some can be a royal PIA, especially if you can't remove the switch to get at them.
The other thing to check, if a continuous string of bulbs is out, is the black ground connection that connects each to each other and then to a common ground. I've never had a bad ground, though: it has always been the bulbs themselves.
JD