After forever (maybe a year?) I finally got around to checking out the door locks on my daughter's cream puff 1994 940 w/ 117K miles.

The car acted just as if it didn't have electric locks. You could lock and unlock all the doors and trunk manually, only the drivers door would require the key. Seemed like a very reasonable Volvo feature. But I was told ALL 940s had electric locks and a lose ground and bad relay were suggested.

The Volvo guy and I had looked briefly and couldn't find the problem.

I could hear the relay clicking when I pushed down on the drivers door lock so I pulled the panel and shorted the leads at the door connector back to the relay, relay clicked but nothing else Then I tried 12 volts directly to the passenger door actuator connector and that's when I realized it was every actuator except the drivers door was burned out.

I pulled all the ones out of my donor car and now she has electric locks. But what a PITA

The actuator are part of the door lock so you need to pull part of the window track and the whole lock assembly to get to it. After about a hour of this I found I could cut it to a few minutes per door by drilling 1/2" witness holes to get to the two screws that attach the actuator to the lock and just reach in and feel around to pull/replace the actuator. The back doors are far easier.

I'm not sure how common of a problem this is, but it's very easy fix (after the first one)

I'm still curious what could burn out all the actuators on a OEM car with no alarms or other aftermarket parts.