traxtar928

I just replaced the recirculation actuator on my early 87.

I checked system vacuum near the brake booster with a mightyvac and I can maintain 10-15inHG of vacuum on whatever is connected to that set of lines. I also hooked up the mightyvac to the blue vacuum line and can open the flap, so the line and new actuator is is functioning properly now.

I've checked all the lines at the small HVAC manifold with the mightyvac, and capped off the ones that have a leaky actuator and don't hold vacuum. When the car is running, the black line that feeds into the small HVAC manifold provides vacuum to the HVAC system. When I put the mightyvac up to that manifold I can't hold vacuum. This tells me that vacuum is getting to the manifold, but isn't being directed to the blue line when the AC is on.

Is there something else I can check? Is this symptomatic of a broken manifold? Some electronic controller has malfunctioned? What should be my next step for troubleshooting?

Kevin in Atlanta

I have the same issue on a 91 S4. On my 87 the flap actuates as soon as I start the car. While working on Kevin Wilson's 87 (Jetson...) I noticed that as soon as the AC switch was connected properly his flap would actuate on startup.

davek9

So one of the solenoids has failed, yes?

soontobered84

Traxtar,
I have spare activation solenoids.

FredR

Apologies if I am missing osmething but is the line to the actuator for the recirc flap holding vacuum or not?

Mine failed so I fastened the flap closed as a temp stop gap- about 4 years ago!

Rgds

Fred

SeanR

You can test the solinoid with ease. It's the furthest one towards the passenger side. Apply direct power to it and see if the flap does it's thing. I've added a switch to this a couple of times to make the recirculation flap do it's thing manually.

Alan

You seem to be missing an important bit of data... exactly how the recirc flap is controlled.

It's good to know how it is supposed to work before you try to check system operation. See the manual for more details and ensure you are provoking its activation. Easiest to be sure of is DEF mode.

Alan

traxtar928

I haven't examined the solenoid itself... It's pretty tucked away behind the center console. Looking at Dwayne's writeup I'll pull the solenoid and test for actuation. Doesn't seem TOO difficult, just a pain to remove everything to get access to those screws.

Alan, my thoughts that the recirculation flap should automatically open with AC operation came from Roger, who tipped me to it when I was describing my AC woes the other day. I'll run through the manual to see when the flap should activate (can you cite a section number from memory??). I do remember cycling through the different settings while the car was running with AC on, and the flap would not open on its own.

Will report back.

Captain_Slow

I read somewhere or was told that the recirculation flap actuates when the AC is switched on.

Kevin in Atlanta

Recirc flap actuates as soon as the car starts with or without the AC switch engaged. If the blue electrical connector is disconnected from the AC switch on the console the recirc flap does not close. This is true in 2 87's. There must be something that actuates the solenoid. Could be the temp slider at full cold?

traxtar928

Kevin, that doesn't make sense to me. If it's default closed, then starting the car would, if anything, open it (since that's what applying vacuum does). The slider is always at full cold, so that's not it either.

Are you saying that the blue wire was disconnected from the solenoid in two models you've looked at? Seeing as how supply vacuum is working, and i can actuate the flap using a mightyvac, I think we can collectively agree that either the solenoid itself is bad, or there is no signal opening it to vacuum.

Kevin in Atlanta

I am saying the flap closes off outside air. That may be the confusion. Sorry about that.

All I know is that it actuates upon start up with the turn of the key for me and Kevin Wilson. My assumption something sends a signal. In the case of the the heater valve it is the setting motor that actuates its solenoid.

Alan

Quite possible you did - there lots of supposition on the web though can't trust it all...

Max cold (full left on temp slider) should cause recirculation as do other temp settings - sometimes. DEF certainly always does which is why I recommend it for testing (but it makes a lot of blower noise and causes other vent changes so audibly it is not so good).

Alan

Captain_Slow

I was told by a knowledgeable person on this forum that AC on set to max cold or set to defrost will set flap to recirculate position.

Does defrost position set the flap to recirculate regardless if AC is on or off?

traxtar928

I dug into it more today. Here is where the vacuum system is. Does anyone have a recommendation for troubleshooting? I'm not sure where to go from here. Does this point to a bad HVAC control unit?

All the solenoids appear to be working, and click over when 12V is applied manually. They do get very hot while activated (open)

(Blue) Recirculation flap only opens when the HVAC is set to 'OFF'
(White) Heater valve is always open unless temp is set to HEAT
(Orange) Center comb flap is always open regardless of setting
(Green) Defroster flap never opens regardless of setting
(Yellow) Footwell flap never opens regardless of setting