so all of a sudden, both rear door locks won't go up/down by pushing switch on master panel...hear 'clunk', but no actuation either way...any hints? hate tearing into a door....master switch less than a year old BTW...

The fact that you hear a clunk tells me your switch is doing something and is very likely OK. Are the lock actuators still stock (as in still have the resistors) inside? Was it hot/had the car sat out in the sun?

funny you should mention the heat Duke...been in the 90's here for the last week...once the temps cooled down some, they worked as they should...swedish electrical gremlins?...

Well I know what your trouble is.

I guess none of us find out about this until it's finally a problem. Inside each door lock actuator, there is a small electric motor that drives it to function. Inside each motor is a resistor, about 9x7mm, & 1mm thick. It looks like a sheath of aluminum on a plastic wafer. They are in the motors the operate very much like a resettable breaker. If someone were abusing your door lock switch, like a bratty kid, they heat up and the lock actuators stop working until they cool down again. Over time they gain a higher and higher baseline resistance that they barely pass enough current to operate the locks. The warmer the ambient temp the higher the resistance. You've probably noticed they have been sluggish for some time.

Now, if you want to solve the problem quickly and have money to burn, have the actuators replaced.

OK, you've got a thousand dollars worth of door lock actuators, so let's get to the real solution.

The only other solution is to pull each actuator and cut off the glued on lids that house the motors and gears, remove the chips and replace them with a suitable conductive material. Many just cut and flatten a piece of solid copper wire from Romex. I did that. Works well. See this link:

https://youtu.be/j_MWPJPJgW8

Kind of a sucky job, but pretty much a permanent fix. Think of the savings and pull the trigger.

wow Duke...thank you so very much for the explanation....who knew?...but your explanation makes it pretty clear..think I'll leave be for now..wound up cracking surround trim when I replaced the door master switch...pulling off door covers would probably go disastrously...but knowing the what is good...'the pursuit of knowledge is it's own reward'...somebody more famous than me..

I know what you mean about the trim. As old as they are, the trim gets pretty brittle sometimes. Those door latch bezels get pretty easy to remove if you are looking at a picture of the trim already removed. That way you know where all the tabs are and just how to approach it.

When pulling to door panels on mine, I always have a razor blade, a sharpie and some silicone 'goop' to deal with the plastic tab anchors that always try to pull away from the door panel. You have to mark the panel however you need to in order to re-adhere the anchor to it in exactly the same place. The razor is the easiest way I've found to get the green factory glue off the panel and the mating surface on the black plastic anchors.

Other than that, be careful with your white plastic arms coming off the actuators. The ones that connect with your door post pins that go up and down to lock and unlock the doors. I filled mine with the same silicone so that if they do break, they are still just as usable since the silicone holds it all in place anyway. See the pic in this link:

https://www.brickboard.com/AWD/volvo/1619988/S70/99_s70_idea_prevent_door_lock_pin_plastic_fastener_breaking.html

Good luck.