A/C Fan Motor Intermittent Failure

We have a 98 V70 with about 85K miles. Recently we have had several
occasions when we have been driving for about an hour with the A/C on low
that it stops cooling. We can feel cool air at the vent but the fan isn't
blowing it around. We don't hear the fan stop, but it does start making a
roaring sound especially if we turn it up some.

Two weeks ago, the dealer changed the fan motor in response to this problem.
But, the problem has continued as if nothing has changed, except that one of
the last two times it happened, we smelled a burning odor. We have found
that if we turn off the A/C for about 10 minutes, and restart it, that it
then runs properly again. The car has gone back to visit the dealer again.

Has anyone run into this problem? What was the solution?

 

Do you get any flashing lights on the A/C unit? If so get them to check out
the resistor pack - it gives the same error code as a failing fan motor.

 

I have a '96 850 with an identical problem, roaring sound and all. To diagnose
the problem, I shut off the compressor and continued to drive. A few minutes
later, volumes of cool air emanated from the vents.

Conclusion:

The evaporator was icing up and obstructing the flow of air. Knowing that, the
question distills down to what's causing the icing to begin with.

Does anyone have any ideas?

BTW, the dealer tried to rope me into changing the blower motor, as well, on
another issue, which was that the fan motor operated on high all the time, even
when the ignition was turned off.

Turned out, as someone else pointed out, to be the resistor. The dealer said it
was a bad motor. (How could it be a bad motor if it was operating very well on a
high setting?)

I straightened it out, but it was a pain and a future cause to be wary of such
misdiagnoses in the dealer's favor.

 

If the evaporator is icing up, then it's too cold, probably caused by
the low pressure switch. If you can measure your low side pressure, it
shouldn't get below about 22 psi (with A/C running of course). If it
does, then the low pressure switch is not cutting the compressor off as
it should. (When the low side pressure gets down to 22 psi the switch
should turn the compressor off until the pressure raises to approx. 40
psi.)

 

This happened on my 2000 S-40. The only advice the dealer had was to close
the cabin air intake when the A/C is on.