I picked up a S90 a few weeks ago that has parking light/turn signal light problems. I have to face this head on so I'll post back in a few days.

My problem is that turn signals do not work when the lights are on and my left signal indicator in the dash cluster shows a steady left signal light on. Also, when the lights are off, the signals work but when you turn on the left signal, the right front one blinks as well. And the reverse lights are alway on with the signals as well. Crazy!

 

Correction, it's not the left reverse light that is on, it's the turn signal light that is staying on. The reverse light is in the trunk lid.

Also, the blue relay in the drivers side trunk area behind the wheel under that small floor panel, does NOT control the blinkers or the turn signals. It only controls the tail lights and brake lights.

I pulled the head light switch and put it in my other car and everything works fine in the other car, good head light swith. I also pulled the turn signal control and took it to the other car and all was well again. Turn signal switch is fine.

So, that leads me to a question... Where in the heck is the relay that controls the turn signals? Rumor has it (from Matthews Volvo site) that the hazard flasher button also doubles as the relay. The think is like 4 inches long so it may be true. I'm going to swap that in my other car and see if the problem follows.

 

Well, I swapped the flasher switch and the switch does stop the turn signals from working but the problem did not follow the car. So I'll be looking for wires under the radiator in the morning.

 

Did you change out the front bulbs? If not change them first I think that will fix the problem.

 

Wow!!! Imagine that, it works...

This was the problem with mine: The socket contacts are pressing hard on the bulb tips. The bulb tips flaten after time and then make contact with each other. Once they make contact they short out when you turn the lights on. Below is a pic of the bad bulb end and a good one.

 

LOL I had a feeling it was that.

 

I am having a similar problem on my 1998 C70 . Battery dead in the morning .checked it and alternator . both check out fine. And have a light inr ear that does not work even when replacing bulb.