So my 2002 volvo s40 the heat just stopped working. Last year I put in a new thermostat in, and my Dad thinks it’s the heater control valve. I’ve been looking around to find out where exactly it is but came up with nothing. I’m probably looking in the wrong places. Can someone help me please? And thank you

 

There is no heater control valve, hot water constantly flows through the heater core - hot air to the cabin is controlled with a blend door, letting more or less air flow through the heater core.

The most common reason heaters stop being hot is the coolant is low in the engine, the heater hoses are very high up on the firewall and when coolant is low the water does not get pushed up there - and no flow.

Your 02 s40 does not have a low coolant level warning system like most other Volvos - so how low is your coolant?

 

Oh ok thank you for the information and it is at max for the coolant level