'01 V70 surging Cabin air (heater core/resistor pack)
 

******EDIT*****I meant Blower motor, not heater core.*****

Ok, I am going crazy. We bought a 2001 V70 about a year ago. With in a couple months the cabin air would surge from high to low/low to high every so often. It does not matter if we have it on heat, A/C or where you have the air directed(IE floor, defrost, dashe, etc).

I replaced the motor under the passenger side dash as I seemed to find that to be a common problem when viewing some of the forums. Well this did not fix it.

The problem has gradually gotten worse. I had read in a forum that it might be the resistor pack that is mounted to the heater motor, so i replaced that today.

No fix!! I am now $250 in parts into this with no fix. :confused:

Any ideas what I should look at next?

First let me clarify my comments, I'm now Volvo expert, but have worked on cars in general for over 40 years. My V70 varies the fan speed by the "request". The bigger the temperature differential of desired temp and the actual temp determines the fan speed. Somewhat dependant on this part of the equasion, is the cars's outside temp sensor. I've read prior posts about the outside sensor playing havoc on the system. So the 1st question is "Is the shown outside temp on the display reasonable"? If all is reasonable here, the the internal temp sensor may be the issue. I wonder if there might be a code in the computer that might help. That is where I might start.

Jerry