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I have a 92 Volvo 240 that has done me no wrong. But there is one thing that has always bugged me. The flow-though ventilation (fresh air) hasn't worked in ages - only recirculation. Which means I keep the fan on low most of the time even at highway speeds for heat and interior windshield condensation.
Well, the other day the flow through started working again as if by magic. I was amazed! But perhaps I hadn't fully woken up when this occurred and maybe my coffee hadn't kicked in properly. So I just had to test the system and set it to recirc for a moment and then back to fresh air. And I got nothing out of the vents, even at 55.
I realize vacuum hoses run the system for the most part, but the switch definitely killed a good thing and now I would like to fix the problem. But I'm at a loss as to where to start. Any thoughts?
I'd start by eliminating any obvious vacuum leaks in the hoses and check valves.
What I do is to pump a vacuum with a MityVac hand pump over a run of the hoses, starting at the vacuum supply under the hood. By pinching off or capping a length of hose, you can test it's integrity, or test a vacuum switch or cell.
Keep in mind that you can actually pull a strong enough vacuum to pinch a failed hose back together, so you have to wiggle the hose section you're testing. Sometimes, you'll wiggle a hose and it will finally snap in two, showing you where a leak may have been, especially when there's a hard plastic line rather than a rubber tube. This is how the intermittent problem may have happened in your car ... a bump in the road jostled a hose and it went back together momentarily to deliver vacuum where needed to cycle the dashpot back to normal position from the recirc ... and then failed again when the vacuum was released on that circuit.
It helps your troubleshooting to have the vacuum schematic for the car, so you can isolate vacuum components and hoses for the testing. If all other functions for airflow are working properly, then you've already isolated the vacuum defect to the fresh/recirc portion of the system.
Thanks ferretkona. Actually, the blower motor works just fine, but they all seem to have that habit of dying eventually. I just don't want to kill it prematurely. I'm aware of the labor involved in replacing that part so what I'm hoping for is a direction to begin with. I'm an occasional poster on Brickboard, so maybe you're right - that's where I should take my Volvo-specific problem.
My problem seems to be either a bad vacuum hose or the fresh/recirc switch as far as I can tell.
I seem to have cross posted with you sunsprit and that's where I shall begin my search. Thanks to both of you.
Well yes - and thanks, pelle. But I'm in the sticks of northern Vermont, which is near... well, nothing really - especially Gainsville, Fl. Actually, I have a good mechanic nearby and he could probably find and fix the problem but I was looking for perhaps a home remedy. BTW - the air was coming in yesterday just fine but only for a little while and then it petered out again. I guess an obstruction could also be a possibility. As yet I haven't found any vacuum leaks.
It might not even be a torn hose, but a loose one. Do the floor/defrost controls switch over? If so, then I would say the leak is either the hose (likely) or the switch (uncommon).
If they don't switch over, then there's a lack of vacuum to operate them. Start checking under the hood for loose/torn/broken vacuum hoses off the intake manifold.
As for the blower motor ... I've done two of those before.
I have done maybe 40 of those motors.... Some bean counter got the bright idea a metal carbon brush holder was too expensive, and so used plastic which getsb hot over time and melts down.
That has nothing to do with the vac switches.
If all the the other vac switches work then the one bad one, is goobered up with some thing. These witches don't have any known problems, so the cure is going to be a easy find. I have worked with volvo since 1970 and so have worked on a good many dating back to the 544. O got out in 85, but the 240 was made then too.
The one I drive daliy is a 240 turbo with a B21 FT engine from 1985. I did the heater motor in that one too.
The other end of the switch goes to vac pod linkage which could be faults as well.
Just pull the 2 screws, undo the plastic screw like cams and pull the dash face off.
Start the engine to get vac, and press the switch, listen and look at the vac lin.... follow where the lines.. There could be difference from 85 to 92 maybe..
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I drive by this place everytime I go over to the VA Hospital.They aways look busy.Apears to be a clean shop also.
