Expert A/C Question

[Shora]

I think that only those who really know their stuff will be able to help me this time. As usual, all help is welcome and really appreciated.

For the last 2 weeks, I have noticed a hissing/ whistle sound going when the A/C is turned off.

The A/C worked fine so I wanted to give see if it would go away on it's own. That didn't work so tonight I was on a mission.

Here is what I found out.

The noise seems to be coming from this item (found below the glove box) and which opens and closes the door responsible for recirculating air from the passenger compartment.

http://i512.photobucket.com/albums/t327/ShoraMarauder/IMG_0370.jpg

http://i512.photobucket.com/albums/t327/ShoraMarauder/IMG_0369.jpg

The problem seems to be that it won't open the door. If I put it on Max A/C and physically push it to open the door it will stay open fine and will also close fine if I push the Normal A/C button. If I push Max A/C again it tries to open but doesn't.

So the door will close fine but won't open unless I push it open.

I thought it might be an A/C vacuum line so I checked the white Vacuum line connected to the back of it and it seemed ok.

Then I took all the vacuum lines off the A/C control unit and reconnected them. Problem continues.

http://i512.photobucket.com/albums/t327/ShoraMarauder/IMG_0366.jpg

http://i512.photobucket.com/albums/t327/ShoraMarauder/IMG_0368.jpg

Any advice?

[Chas1955]

The unit is a vacuum actuator kind of like a motor that works by vacuum. The internal bladder may have a hole causing a vacuum leak which would explain the hissing sound you hear and the fact that the actuator doesn't open the door makes me think this is your problem. You can pick up a vacuum pump/brake bleeder from you local parts store for about fifteen to twenty bucks. Attach the vacuum pump to the actuator vacuum outlet and pump it a few times to see if it opens the door. If it does your leak is somewhere else. If it doesn’t the actuator is defective and needs to be replaced. Hope this advice helps.

[Shora]

The unit is a vacuum actuator kind of like a motor that works by vacuum. The internal bladder may have a hole causing a vacuum leak which would explain the hissing sound you hear and the fact that the actuator doesn't open the door makes me think this is your problem. You can pick up a vacuum pump/brake bleeder from you local parts store for about fifteen to twenty bucks. Attach the vacuum pump to the actuator vacuum outlet and pump it a few times to see if it opens the door. If it does your leak is somewhere else. If it doesn’t the actuator is defective and needs to be replaced. Hope this advice helps.

This is really good advice. Thanks.

Welcome to the site. :beer:

[cv2000pi]

I Second Chas1955 diag. You might spend a little more but purchase a MityVac (its a handheld pump/vac system). Detach the factory line and pump the handle it should hold the arm in a fully open/closed position, if not your part is bad. It is an excellent tool to have in your toolbox to bleed the brakes after a complete line replacvement or to apply vacuum to an old style vacuum advance on a distributor or working on old cars with vacuum headlamp doors.

[Dennis Reinhart]

When cars have a AC and a Max AC mode this is controlled by a blend air door that closes in the Max AC mode, allowing only the air in the car to be recirculated. When you shut the car off, when the AC is running the high side is at at about 250 PSI the low side is at 40 PSI when you shut the car off the high and low side equalize through the orifice tube and this can be heard as a hissing noise as well.

[Shora]

Well, I got back from Advance Auto Parts and they don't have what I need.

What sucks is that I threw away this brake bleeder kit a few months ago because it was a POS but could have been just right to test this A/C item.

http://www.mercurymarauder.net/showcase/files/3/5/1/3/157_5785.JPG

[Shora]

Update:

Good news. I went to a junk yard today and pulled one of those suckers off a 1994 Town Car and they only charged me $4.00.

Also, I met up with my good friend RoyalPITA and he changed out my driver side rear door lock accuator (or however it's spelled). If I had to pay him a nickel for every jam he got me out of I too would need a government bailout.

Thanks guys for all the help and advice.

Cheers.
:beer:

[Mike]

Update:

Good news. I went to a junk yard today and pulled one of those suckers off a 1994 Town Car and they only charged me $4.00.

Also, I met up with my good friend RoyalPITA and he changed out my driver side rear door lock accuator (or however it's spelled). If I had to pay him a nickel for every jam he got me out of I too would need a government bailout.

Thanks guys for all the help and advice.

Cheers.
:beer:

Gotta love this site :D

[Marauderjack]

I thought that blend door doodad required complete dash removal to replace??:confused:

[GetMeMyStogie]

No need for a vacuum pump if you have a piece of hose and a couple of plastic vacuum hose connectors (or simply a couple pieces of some small diameter plastic tubing, or even one long (maybe 8") piece of flexible plastic tubing) lying around. Stick one connector into each end of the piece of hose. Disconnect the vacuum connector from the back of the EATC. Start the engine. Stick one connector into the EATC vacuum connector black line (the vacuum source), and connect the other end of the hose to each one of the other 4 coloured hoses sequentially. This test basically bypasses the EATC, while enabling you to test each vacuum motor in the HVAC ductwork individually.

Odd thing, imho, to get a leaky HVAC vacuum motor. I've had several full size fords last well beyond 10 years without something like that happen. Bad luck, I guess. Or, maybe the problem is in the EATC - it's very common for them to wear out and start leaking. Have you seen the sticky about repairing your EATC (http://mercurymarauder.net/forums/showthread.php?t=36922&highlight=vacuum+o-ring)?

[Shora]

I thought that blend door doodad required complete dash removal to replace??:confused:

This is not the blend door.

This item is found below the passanger's side glove box and is used to open and close a small door up in the footwell area. This door opens when you set the A/C to the Max setting to allow the A/C to recirculate the cooler air found in the cabin rather than to work harder trying to cool the warmer outside air.


No need for a vacuum pump if you have a piece of hose and a couple of plastic vacuum hose connectors (or simply a couple pieces of some small diameter plastic tubing, or even one long (maybe 8") piece of flexible plastic tubing) lying around. Stick one connector into each end of the piece of hose. Disconnect the vacuum connector from the back of the EATC. Start the engine. Stick one connector into the EATC vacuum connector black line (the vacuum source), and connect the other end of the hose to each one of the other 4 coloured hoses sequentially. This test basically bypasses the EATC, while enabling you to test each vacuum motor in the HVAC ductwork individually.

Odd thing, imho, to get a leaky HVAC vacuum motor. I've had several full size fords last well beyond 10 years without something like that happen. Bad luck, I guess. Or, maybe the problem is in the EATC - it's very common for them to wear out and start leaking. Have you seen the sticky about repairing your EATC (http://mercurymarauder.net/forums/showthread.php?t=36922&highlight=vacuum+o-ring)?

I am still not 100% sure how to do the test that you mentioned, but I am 100% sure that the problem is not the EATC since I replaced the vacuum thing (picture in first post) and now all is fixed.

Thanks for the advice though. It may help for a different issue down the road.

[TAKEDOWN]

What a guy that RoyalPITA! I'm glad he's on my side!

[omarauder]

These hand vacuum pumps are very handy for troubleshooting any vacuum devices and hoses/lines. Just pump up about 20" Hg vacuum which should move the actuator fully. Monitor the gauge and it should hold this value for a long time. If it drops to zero quickly you have an internal leak.

[CKMustangCobra]

This thread has narrowed down my search to an issue I have with my A/C.

Whenever I turn the A/C on I heard this really loud bang from behind the A/C unit. It sounds like a small door slamming...

I guess it is the blender. :/