This is usually related to a failed vacuum check valve under the hood. It is connected to a large hose that runs directly to the throttle body. If it's stuck shut, the default is to direct the air to the floor plenums only, since you're not getting a vacuum feed into the control unit. Check by swapping in a known good unit or for a very quick check, remove the valve and install the hose directly onto the other line running into the car. If your modes work, that's the issue. If they still don't work, then the hose leading into the control unit is broken. If the hose is ok, then you're going to need to check the control unit itself (go to any pick-a-part, these can be had for a few dollars and I've rarely seen a bad one) and test by swapping it out. If that's ok, then it's time to check the vacuum motors and their connections and that can be a pig since you'll need to remove some interior components to get at them.
SOURCE: No air coming through vents and blower is OK
your blower motor might be damaged.replace the blower motor of the air con.
SOURCE: 97 Volvo S80 heater works but will only come out of dash vents
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.
SOURCE: Electronic vent control not working in Volvo S40
Hi,
I think here, by your description, that there might be something that has slipped inside the vent holes from outside. you can try to blow some compressed air through the vent holes at the bottom of the windscreen.
Otherwise you can try to look under the dash, activate the switch and see if you can locate from where the noise is coming and see if you can reach the mechanism that control the vent. Normally it must be moving free. Otherwise your local mechanic should be able to fix that ufor you.
Cheers.
Technopro
SOURCE: defrost is not working. Volvo 1989 sw240
You have a problem with the vacuum operation of the dampers that control the direction of the airflow. You will need to pull the front panel of the console and look at the vacuum hoses that attach to the back of the control buttons. If those are attached, look under the dash to see if they are attached to the small bellows that control the dampers. You should pull the glove box out so you can see the damper under the dash to get a look at it and get an idea for how the other one looks. There is a second damper to the left of the one behind the glove box. Behind the bellows there is a small nipple that any loose hoses should be attached to. Take a flashlight along when you start exploring. If those are okay, check the other side.
Your Heater Core is Bad= Coolant on Pass Floor
If A/C Does NOT blow Cold anymore the Evaperator Core is Leaking
First time I have seen them BOTH go Bad in 30 rs of Bein A Mech/Tech
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