So long story short, the front defroster on my 240 hasn't worked for a while. Air isn't coming out. I live in the midwest, so I need to fix this. How should I start diagnosing it?

Thanks again, you guys rock.

Edit: I do have a disconnected vaccuum hose, its the one on the throttle body, but at the risk of sounding stupid i'm not exactly sure which hose it connects to

 

That vacuum hose is probably the one that operates the heater direction doors which explains your problem. There aren't that many vacuum hoses on a 240. Just Google a "vacuum hose diagram for a Volvo 240", you will get it.

 

There is a vacuum block behind the controls for the vents. You could have a leak there, or might be disconnected. You have to remove the interior panels to see them

It is in this lower area:



Do any of the other vents work?

 

it would help to say what year 240, as there were a few different heater/ventilaition/airconditioning control panels through the years, but yeah, most all of them are vacuum activated. with no vacuum, you'll get air from the central dashboard vents. on the most common middle/late years control panel, the defrost button opens the vents on top, while the heater button opens the vents on the bottom for foot/floor heat, and of course, the fan speed switch controls just how much air you get. oh, and the recirc button closes the fresh intake from the cowl.

 

Sorry, its an '88

I definitely connected the right vaccum hose, going to the charcoal canister underneath the car, still no change.
My floor vents are working fine. I might open up the dash and check for a leak there.

 

I think #38 above is the bellows for opening the defroster vents

#32 above opens the heater vents above your feet.

this is the exploded rest of the system,


#7 on that is the recirc control, and #12 is the rear floor heat..

 

awesome, thanks pierce!

I looked online, and even with my masterful google-fu, I couldn't find anything resembling these. Almost everything was for 850/940s

 

The vacuum line that runs the flaps for the heating/cooling connects to the top of the intake manifold. You should see a black/white plastic check valve there that connects to the intake manifold with a large hose. It has then a smaller hose that runs through the firewall on the passenger side of the car.

I would first check to see if you are getting vacuum inside the car. You should be able to see that hose where it comes in if you remove the kick panel on the passenger side of the center console. With the engine running, disconnect that hose from the vacuum reservoir in the console and see if it is pulling a vacuum. If it is, then start checking the hoses where they come out of the 3-button flapper control.

 

my defrost wasn't working and i consider this an emergency situation living in the northeast. personally i would rather be able to see the road than have toasty feet. anyway, instead of messing around with vacuum lines i did the following:
on the vents there are vacuum actuators with levers to direct the air flow to the top defrost vents. i pulled the glove box and turned the lever manually to full defrost position. pulled the instrument cluster to get at the driver's side vent and did the same thing. the controls on the dash are all set to off or full out if you will, and i don't ever touch them. air now goes full blast to defrost vents if all the dash vents are closed. no or very little air goes to the floor vents.
i can still get heat from the dash vents by opening them manually as needed.
this is working very well this winter. maybe someday i will look at the vacuum lines to figure out where the leak is.

good luck

 

(from memory) the vacuum comes in through the firewall, goes through a 1-way valve and into a 'reservoir' (looks like 4 ***** in a row), then from there to a series of T connectors, that connect up to the control button block. then from the control block, there's a vacuum line to each actuator/bellow.