Hi I am new here and very new at working on a Volvo. The heat/ac suddenly stopped working. Doesn’t blow at all when I turn it on. Fuses seem fine. I thought maybe it was a relay issue but I can’t find which one it is. Any ideas?

 

Model, year?

 

my bad. It’s a 1992 740 turbo

 

There is a relay clipped by the headlight, 2 actually, one of them is for the fan. Forget which side they are on but they are there, can't miss them...

 

isn't that relay for the engine cooling fan?

I believe Jor is talking about the HVAC fan under the dashboard.

There's 3 different heating systems, the manual heater without AC, the manual combined heater/ac, and the electric climate unit. since you mentioned AC, I'm going to assume you have the manual combo system

power goes from the ignition switch to fuse 16 (behind the ash tray) and from fuse 16, it goes to the control panel.

the fan switch has 5 positions. position 5 connects the power directly to the fan motor, while positions 1-4 connect the power to various 'taps' on the fan resistor module... this is behind the glovebox, mounted on the outside of the air housing near the fan motor. if you get fan in position 5 but not in 1-4, then that resistor is probably the problem.

if you get no fan at all in any position, then its either the fuse 16, or its the fan motor itself... if you ahve a volt meter, connect it to resistor pins 1 and 2 (white-black and red-white, either of the two lower 2-pin connectors), and turn the fan on 5 and see if there's 12V at those pins. no juice and the problem is in the switch or the power supply. if you see juice, then its probably a bad fan motor.

 

Yeah, right, HVAC fans... sorry! Yeah, either the motor, or the dash "controller"... Check fuse first, of course...

 

with the manual combination hvac, the fan switch is separate from the hvac controller.