I have a minor problem. When I turn on the head lights, the "burnt" bulb
indicator light comes on, and stays on until I press on the brake.
At that point it goes out, and stays out.
I have checked all the lights, and all are fine.
Any ideas ?

I just went through this awhile back. My bulb failure light would come on when I pressed on the brakes during the day (headlights off) and would come on all the time at night (headlights on). So, I would replace a tailight that was out. This would fix the problem for about a day and then the bulb failure light would come back on. A different taillight would be out.
I finally bought a complete set of tailights, indicators and running lights. Before replacing the bulbs, I cleaned the copper contacts. I ran my fingers across them and the contacts were greasy! Nothing visible though. Replaced all the bulbs. Turned on my headlights and guess what...the bulb failure light came on!
I walked around the vechile, all lights on. Had a friend press on the brake pedal while was behind the vechile, all the lights came on.
I replaced the bulb failure relay (www.gapa.com...about $30-$40 I think) and haven't had a problem since.
Another note, I believe there is a set of fog tailights that will not come on unless it is switched on, the switch next to the head fog lights.
I have been told that those relays go out after about 10 years.

Chas.
'89 740 Turbo
175,000 miles

I have a similar problem. But it's not just the brake and headlights, but also when the turn light is on and the brake is pushed. I have been aiming to the relay. I have not looked into this problem much, but seeing your post I hope someone will verify the relay thought.

Larry

If any of the bulbs are a different type or the sockets corroded this will happen. The "relay" bulb out sensor measures resistance in the system that is being used at the time and reports an outage if the measured resistance isn't correct.

Also bulbs placed in backwards will sometimes cause this problem. Had my brake bulb in backwards so that it burned when the parking lights were on. The burn-out indicator read the change in voltage on that circuit as a blown bulb.

Understood, but my out indicator only does this when it cold out(morning)

I am having a similiar problem. When I want to make a left turn, after about 2 blinks the bulb out indicator comes on. I have chasing a ground problem in the left front ground block for some time. At one point last week, if you turned on the headlights all of the wipers would come on. After cleaning the ground block that stopped happening. Sort of. Now the bulb out indicator comes on only when the left directional is on. Also if I flash to pass, the rear wiper still does one swipe. I am going to replace the spade connector for the light ground in that corner since I couldn't really clean it. It is still somewhat corroded.

In short, check the grounds if you are sure the bulbs are the same type and installed correctly. Volvo loves using common ground blocks. There is one in each of the front corners and at the bottom of each A pillar inside behind the kick panels and I believe the tail lights are grounded directly to the chassis in back (maybe someone else can verify this). Also look for a light that is dimmer than its twin, it might be a bad bulb.

Just my 2cents.

-Chris