Hi Guys,

I'm new to this forum, looking forward to contributing.

My 2005 S40 T5 AWD has started having an issue with the heat where it will not blow hot air unless the rpm are above idle. Even after a 1hr drive, the heat will blow hot only if rpm are up. I had the coolant flushed at the end of this past summer and wonder if there is some air pocket that could be causing this. the other thought I has was that there could be a vacuum hose that could have a stuck/malfunctioning valve, but I don't know enough about the heating system to diagnose. Hope someone on here has seen this before.

Thanks Guys!!!

Tom

 

My 2006 S40 had a problem similar to this, noticed it before I took delivery and the dealer I was purchasing from it couldn't figure it out so they sent it to the nearby Volvo dealer to get it fixed. They said they re-calibrated some "damper motors" and cleared some related faults. I too thought it was some sort of vacuum problem, but I now suspect the air system in this car doesn't use vacuum actuators.

In my car when I would accelerate briskly for a good bit (say over five seconds), the air would completely stop flowing though the vents. As soon as I'd get off the gas and slow down, within five seconds or so, the air would come roaring back. Not exactly the same as your problem, but similar enough it may have the same root cause.

I realize this doesn't really help you fix this problem yourself, but hopefully points you in the right direction.

 

Mine would blow cold air due to low coolant. Check the coolant reservoir in the engine compartment.

 

Thermostat stuck open even if the temperature gauge is right at the middle of the dial. The coolant that warms the blower air, doesn't have time to get hot enough because it's continuosly circulating through the radiator. When the engine revs, it gets hotter and transfers more heat to the coolant.