[LaurieB]

Nice design using a stopper, I would guess if conducted and calibrated properly that would be a robust fix, however I am perhaps to lazy to do this job properly.

I have adopted a slightly different, perhaps easier and less complex approach. Rather than an electrical engineer I am a metallurgist/mechanical engineer, just for the record.

My approach is based on the assumption that the variable swirl system in question is not measurably sensitive to one or two degrees of butterfly valve rotational variance. I am guessing it mostly uses completely closed, completely open and maybe three or four different positions in-between.To support my assumption without going into fluid-mechanics, I would argue that the original Volvo design is not a true servo system, and therefore is susceptible to a considerable amount of rotational drift itself, particularly in between calibration periods, therefore Volvo obviously decided that this system did not need to be accurate to 1-2degrees.

So I thought why not use a really ductile and tough piece of wire, to act a bit like a spring between the actuator and valves, I used a keyring that I uncoiled and looped round the ball on the actuator arm and hooked on to the valve actuation arm on the block side. This system means when the actuator is fully open the valves are fully open, and when the actuator is fully closed the valves are fully closed. However in between open and closed positions I would estimate there could be 1-2deg of rotational drift.

The fact the linkage is so flexible means that it is practically impossible for any components of the linkage to be excessively stressed and fracture.

I think the problem allot of people, including Volvo it would appear have run into, is that they assumed they needed to make a bigger stronger linkage, which then breaks because the excessively powerful actuator loads it up when it drifts and when it re calibrates. The true culprit of the failure however is the inaccuracy of the actuator, and to solve this you need a flexible linkage. The forces needed to actuate the butterfly valves are minute, so a small piece of wire is more than capable of transferring the required load.

My Keyring fix is working fine for solving the performance issues (Was very down on power), just need to get the error message removed at some point, I will report back if the message returns. Although I am highly doubtful it will as I am sure that the 1-2deg of variation will have no significant effect on the flow through the system, as the turbulence are so unpredictable anyway. There is no chance that an AMFS with a +/- 15% tol will be able to pick up a tiny variation in the swirl valve position.