Blower motor slows when under acceleration

[Van I]

When I have the AC/ or heat on and the blower on at any setting, when I accelerate the blower slows down almost to no air flow. What could be causing this and how can I fix it?

Thanks for any help
Van I

[LaRy]

What kind of Volvo is it, 240, 740 or 940? Do you hear any odd sound like the fan is hitting the walls or do you just notice that it slows down?

[Van I]

It's a 960, i am pretty sure its a vacume leak (vacume servo is what i suspect)

[Volvord]

My thinking exactly. The problem is probably not the motor, but actually a vacuum leak causing the ventalation system to "change" to defrost under accelleration. Check for loose hoses, also check the function of the one-way-valve from the vacuum resevour