90 XJS coupe, the recirc flaps never open.
They can be opened by hand against spring pressure.
I keep reading in the various Delanair III tech documents that
they are held closed by vacuum but I can’t see how this would be
the case? Can someone tell me how these should behave?
I’m assuming closed when the car is off since there is no vacuum,
and closed when the system is switched off, and open when max
cooling or heating is requested?
The upper (fresh air) and lower (recirc) flaps are connected with a link so they operate together. IOW, when one opens, the other is closed. When the engine is not running the upper flap is open, and the lower is closed. When the engine is started, vacuum closes the upper flap and the lower recirc flap opens. That is the default position, whether the climate control is on, or not. If the climate control is energized, the upper flap stays closed, and the lower recirc opens if full cooling or heating is demanded. As the temperature in the car stabilizes, the upper fresh air flap will open. Hope that helps.
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Excellent, thanks. Mine is clearly not working lol…
Vacuum controlled per Dave’s description; solenoid is on left side of HVAC main housing. One side of each of the 4 solenoids is fed constant vacuum via a reservoir and check valve on the right side of the vehicle. Refer to the above diagram for solenoid location. The switched side of the recirculating control solenoid tees and goes to the diaphragm on each blower housing. A disconnected vacuum line in any of that will prevent operation.
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Well at a minimum the driver vacuum actuator is bad, didn’t have time to pull the glovebox to get to the passenger one.
What a tedious job. The driver vacuum servo was bad, replaced it with a spare and recon’d the blower motors and speed controllers, all seems to be working now.
There was fair evidence of water (and red Oklahoma dirt) entering from the passenger side cowl, the seals were good near as I could tell, I added some black butyl string sealant to the sealing surface on both of them. Maybe it’ll help. Good thing this car is parked indoors these days.
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