I have a 93 850 GLT. I just purchased this car. This is my first Volvo.The heat does not work. I have the dual climate control with the auto heat control dash unit. My first thought wasthe blower motor was worn out. I did test on the blower motor and it works fine. In my test I learned that the heating system works off of the ground system to turn the blower motor on and off. I then switch out the whole control unit in the dash. (with a used one) I still have the same issue. I can see and hear the electric componets opening the flaps in the heaterbox from floor to defroster. I felt the hose's coming to and from the heater core and they are hot. I have grounded the fan to the body just to blow heat. The only thing that happens when I do this is I get cold air from all of the vents. Can someone help me find out what is not working.

 

heater core is most likely bad, check to make sure that the heater core is ok, and that it has not been bypassed, it will not heat unless the engine is warm, so make sure that your engine is running and warm as well

 

Do you hear and feel your blower running when you put it in manual mode? While the motor may be good and the component switches good there is a resistor mounted on the heater box right next to the blower motor... if it is bad you will not get motor movement, no matter how hot the engine gets...

GL

 

If your fan is not blowing and will only run when you ground the blue wire the problem is with your power stage which is also (incorrectly in the case of the ECC) called the blower resistor. They are expensive little devils but I guess they are cheaper than frostbite. The power stage is inset into the main air duct, between the blower fan and the shelf with the A/C relay and it is held in place with a torx screw. Tough on the wallet but a very easy repair.

...Lee

 

I am looking for the location of my blower risistor. I would like to know specific location such as left or right side of the blower, number of pin connector and/or wire colors.

 

For a North American (left hand drive) car they are to the left of the blower as you look at it through the glove box hole. The style of connector(s) depends on which type of climate unit you have. It is the only thing that is screwed into the air duct if that helps.

...Lee

 

Thanks for your words of wisdow. I got the part from the junk yard for $10 and the heat works great.