Reduced air through defrost vents

Hi Ken,
Thanks for the reply. I actually read this article prior to contacting you. I traced as much of the vacuum lines as I could see but did not find anything clearly broken. I will check again and get back to you ASAP.

Thanks again,
Eric

Hi Ken,
I double checked everything under the hood. I did not see anything obviously broken or cracked. Here is what I found under the hood as best I can tell. There is a main tube that goes from the engine (near the PCV or EGR valve at the back of the engine) that goes into what I believe is a check valve. Off the top of the valve is a small hard black plastic line. Below that is a larger (3/8" - 1/2") rubber line that goes to a black box on the driver's side just ahead of the cruise control. Below that line is a round disk shaped part of the valve. Below that is a port with a rubber cap on it. This is directly across from the tube coming from the back of the engine. The next line below the capped one is a larger rubber line (3/4"?0 that runs to the brake booster. Below that line at the bottom of the valve is a yellow line that meets up with the thin black line from the top of the valve. These two lines make their way into the driver's compartment near the accelerator pedal. The lines then split, the yellow line goes up into the steering column then returns as a white line to the actuator for the parking brake. The small black plastic line continues under the dash/ashtray/cup holder and into a white plastic disk-like device that has all the vacuum lines going to the two actuators (what I call the left and right) as well as the actuator on the passenger side for what I believe is for the defrost. Then the small black line goes with all the vacuum lines on the other side of the white disk into the control panel. I bought another of these a while back but haven't yet replaced it. It is a Motorcraft YH-380 (E1AZ-19B888-B) A/C Valve. That is what I can tell you regarding vacuum lines. All seem in good shape and securely connected. Okay, now this is what happens with actuators left and right when the car is running and I switch the lever from off through defrost. Note the lines going into left are red and yellow and the line going into right is blue. First in the off mode, left is fully in and right is fully out. Next, Max A/C, left is in and right is in. Next, norm A/C left is in and right is in. Next, vent, left is in and right is in. Next, floor, left is in and right is out. Next, defrost/floor, left is out one notch and right is out. Lastly defrost, left is out two notches and right is out.

Thanks again Ken. I hope this helps and I appreciate yours,
Eric

Hi Ken,
I need some clarification on your request. When you say "at the rear of the vacuum valve" do you mean the check valve under the hood at the firewall? If so, do you want me to disconnect the tube at the check valve (to the engine) and check for vacuum at the tube while the engine is running? As for the blower motor, it works at all speeds (unless you want me to disconnect the tube and see if the blower speed changes)? Also, I am not sure what I am looking for on the illustration but I see it is for an ATC. My car has a Manual HVAC system as far as I can tell. One more thing, I see illustrations mentioning a cable that goes from the HVAC Control panel to a Temperature Blend Door but my system has no cable. Mine must be electronic like this illustration shows at the lower right. The illustration appears to be similar to what I have. The part number on my Control Panel is F3AZ-19980-A.

Thanks for your help Ken,
Eric

Hi Ken,
Although I could reach the line from under the ashtray area, I was not able to get the line disconnected. I tried pulling and twisting it but all I was able to do was break the seal of a rubber base that holds all the lines to the HVAC vacuum control. I will remove the control or the whole unit this weekend and see if it is any easier that way. Are there any tricks to removing a vacuum line? I may have damaged the black line trying to remove it. I will find out tomorrow morning on my way to work.

Thanks again Ken and I will let you know what I figure out,
Eric

Hi Ken,
I ended up removing the A/C Valve from the Control Unit and then pulling the cluster of lines off the Valve via the rubber block. I started the car and could hear a hiss and could feel vacuum from the black opening. I also hooked-up my vacuum pump to check how much vacuum I was getting and it showed between 18 - 19 in. Hg? Seeing as I now have the valve out, when I put things together again I might as well install my new one, right?

Hopefully this helps with the diagnosis. Let me know what to do next. I appreciate your help.

Thanks Ken,
Eric

Hi Ken,

I used a jumper and all seems fine. I think there may have been a better seal with the jumper because the actuators seemed to move quicker and also the actuator with the blue vacuum line made a much more pronounced click when it was fully inward, almost like it was hanging up on or getting caught on something. All actuators moved inwards when vacuum was applied (the red moved one "notch" and the yellow moved two "notches"). It is impossible to see the end of the blue line's actuator arm due to it being enclosed in the large "black box" under the dash. I can see the arm moving but can't see what, if anything, it is getting caught on or even moving.

Let me know what you would like pictures of. I will try to take some. I will be re-assembling my HVAC system in a few hours so I can use it driving to work tomorrow.

Thanks Ken,
Eric

Hi Ken,
A quick update before bedtime. I re-attached the cluster of vacuum lines to the new A/C valve but also put a thin strip of rubberized two-sided tape on the base of the block to help with sealing. I cleared all the ports and re-assembled everything but it still does the same thing.
I will be anxiously awaiting your next suggestion.

Thanks again for your help,
Eric

Hi Ken,

Yep, the fan is good. I replaced it about a year ago. I get plenty of air movement just not through the defrost vents. I will try to shoot a video and show you what is going on.

Thanks,
Eric

Hi Ken,
I can hear the vacuum hiss and clunking of doors when I move the selector through its different positions.
I shot a video, although I had to stop a few times, so it is on four different videos. I think it will show my issue. You may be able to notice on the right actuator, the arm moves up and down slightly as it moves in and out. I do not know if that has anything to do with my problem or not. Too bad I cannot see inside that black box.

Thanks again Ken,
Eric

Hi Ken,
Wow, not what I had hoped for. This looks very involved. If I get the chance to do this, I will let you know how it turns out.

Thanks again for your help,
Eric