Heat and Vent fan in Volvo S80

check fuses first?
that is rare, mostly it is backwards from that.
the controller , is the car with the the climate control option
or manual heater controls?
2 systems and not the same

read the manual use a voltmeter to find fail point

https://eautorepair.net/Marketing/Default.asp

Hi,
These are usually related to a FUSE. In the OWNER's MANUAL look for the FUSE section and see if the non-working devices are listed on the same fuse, and where the FUSE panel is located. Fuses can be purchased @ an Auto Parts, Hardware store or the dealer.

It could also be a relay for these devices. Look online in the Volvo Forums for more info.
TD

When the blower works only on the high setting its usually a bad blower resistor which is right near the blower motor. now you say it would always blow high regardless of the fan speed setting that would indicate probably the climate control unit or a connector problem somewhere. finally it not working at all may be the climate control unit or connection went bad even further. it might have a blown fuse or a bad blower motor in addition to the climate control unit or connector problem .check for power and ground at the blower motor. the power is supplied from fuses and may have a relay also. the ground is supplied from the climate control unit and goes through the resistor to control the fan speed. good luck

Blown Fuse

• Usually the first thing to inspect when the blower fan stops working is the fuses to see if any are blown. Locate the 10A cluster fuse or the 25A HVAC fuse in your car manual, and examine them to determine if they need replacing. The car owner's manual will tell you where to find the fuses that are connected to the heat and/or air conditioning. On the interior fuse panel of the car, a 30 amp fuse is labeled "Heater" or "HVAC."
  

Bad Blower MotorIf the fan only works on setting number 3 or 4, or just on the highest setting, it is most likely that your blower motor is failing and is about to die. Use a voltmeter to test the amount of voltage at the blower motor connector with your ignition on and AC running. If it reads 12V, the motor needs replacing.Automatic Climate Control SystemAnother thing that causes the blower fan to malfunction is the Automatic Climate Control System (ACCS). If the ACCS's settings are off, it may cause the fan to stop working. If it is the climate control on the car, typically it is a bad thermostat or electrical circuit that is the culprit.
hope this helps, James Booth

I had the same problem with my 2001 s80 my battery went dead and it just stopped working me and a friend looked at every fuse even all of the relays and the relays under the fuse box in the engine compartment but to do that you have to remove the battery terminals so when we were finished checking everything we connected the terminal and started the car and everything was back on I'm assuming that the computer or something needed to be reset.

Which fan motor do you want to repair, the one inside the car for climate control or outside for engine cooling next to radiator? Inside locate fan please note some libraries have repair manuals that you can check with them for free you usually can go and find at least the location this way. Check fuse location and electrically check BOTH SIDES of the fuse with a digital volt meter not a test light some circuits in newer computer control vehicles can be damaged by test lights. Once you find the fan (inside) it also has a resister pack usually somewhere on the a/c heater assembly, check for voltage at the input of the motor AND the ground side also remember electricity needs a complete circuit.
If outside cooling motor look for a fuse box outside in the engine compartment and check that also inspect the wiring connections in line for melting usually at the motor this is a tell tale sign that the motor is using too much current. Also there needs to be a temperature switch in the cooling system sometimes in the radiator or in the engine/block/head. watch the color code of the wire from motor trace back usually to a relay or two speed resister block. Also some cars have a secondary fan for the A/C condenser I assume you don't mean this one.

The fuse for heater/ac fan is number 36.30 amp located end of dash
If this is ok,you need to replace heater control module behind heater controls.Save money buy haynes manual,check e bay

if the fan is blowing this could be a problem with the climate controll switch that changes the direction of air from floor to defrost to vents, some are vacuum controlled through a vacuum operated mechanism that opens and closes a door in the vents which redirects the air to different places.

Your CCM (Climate Control Module) is dead, or asleep. Look in the fuse box at the left end of the dashboard and pull the fuse and see if it resets the CCM. The module may need to be reprogrammed or replaced.

My suggestion is that you take this to a Volvo mechanic, one who has experience with working on these 1999- Volvo models. They have a networked computer system that requires special tools to diagnose and download software into the modules.

Also, it is a good idea to have them perform a total software upgrade, it will address many issues, and may prevent other issues from occurring.

Bret
RepairPal.com

The heater controls would be the first thing I would check, and then the actuators for the mode door(s) would be the next. There should only be one heater fuse.