We have 2001 S40. We noticed a few weeks ago when the heater was on the high temp it was still blowing cold air we would have to move the dial and after a while the heat would come back on. Sunday when I turned on our the heater and it worked for a like 5 mins then shut off . I moved the dials to change the temp still no heater. Same thing Sunday night I let the car warm up and Still no heater. Yesterday the heater worked after an hr of running then worked all day but last night it had stopped working and hasn't worked today thus far.

Any ideas what it might be?

 

What is the engine temp at?

 

About half - I read on one of these threads that if the coolant was low that could have something do with it. So on Sunday night i did added coolant and it worked somewhat Monday.

 

Mine quit working with low coolant on a 2005 model. Not sure with a 2001 though. It sounds as though your engine temp is correct at half way on the gauge. Does it run cold with a full coolant reservoir? Maybe check for air in the system?

 

I just checked reservoir is filled with coolant.


We checked both fuses and they were both good. Then we took out the old motor and tested it on the battery (connected to 12V) and the fan worked. So this had led us to believe that it is the resistor. Using a voltage meter we checked voltage on resistor by moving the dials and the voltage output did not change.

NOTE: The blower motor in a 2001 Volvo S40 was easy to access under the passenger side dashboard. No need to remove the glove box. The motor is held by 3 screws.

 

Ok, the problem is no air blowing? By no heat I thought you meant it was blowing cold air.

Are you going to change the transistor with the low cost Radio Shack option? Mine has quit blowing air twice now. The first time I replaced the whole resistor/heat sink as sold by Volvo. It was $79 way back when. This latest time I decided to try replacing just the transistor portion. So far it has worked flawlessly. It's easy too. You need some small tools like a computer tool set or eyeglass tools and a soldering iron, both very low cost.

Resistor:


2N3055 NPN Transistor: