Hello,
I have an interesting problem. Normally, as far as I have read, ac vent failures usually default to defrost, but mine seems to be stuck coming out of front vents only. Read something about the lower-mode vacuum actuator. Can someone help me diagnose the problem?
Thanks.

 

you will need to get a manual and look at the vacuum diagrams, As well as the vacuum selector switch in the hvac controls.

 

Thanks for replying. Yeah, I do need to get myself a service manual

 

UPDATE.....
Well I be.... It was the freaking vacumn selector behind the ac controls. Didn't believe it because I always read a leak makes it default to defrost only. Did the bolt mod just to clear up the hiss and ...... Max was blowing harder than I ever had it blow since I bought it. Tried the other modes and they all work now as expected. I know I didn't have but the one comment, but i thank the forum as a whole because the solution was here all along.
Tjanks.

 

Curious, what's the bolt mod you speak of?

 

Here is the link I followed.

 

That's great information, thank you for sharing!

 

Fantastic, thanks!

 

I have a similar problem. I changed the cap and rotor and separated a vacuum line. Now I cant get any airflow through the interior vents. I attached a pic. The pic is of a 3-way line connector where one of the connections is broken. Is it just a 3-way connection or does it do something else? If so what do you call it? I have a early 80s Haynes manual, but don't seem to find a applicable vacuum diagram. (The car is a '87 V-6 EFI) Can I replace the connector or should I try to rig a repair? Appreciate any tips.

 

That part is called a three-way vacuum check valve. Dorman still makes them.

 

It's a check valve with 2 ports on one side of it. You can accomplish the same thing with an ordinary 2-port valve and a T. The end with 1 port goes to the intake manifold; the 2 ports on the other side together go to the cruise control and the HVAC controls.

In any case, you can find one hanging on a card in the Help! (Dorman) aisle of your local corner parts store. Sometimes they have them by the PCV valves (in the filter section) also.

 

Thanks for the feedback guys. I found a Dorman 3 way check valve at my neighborhood chain auto parts store today (see pic). Good thing, the original was so brittle the hose barbs came out in pieces. I'm happy to say it worked and I now have airflow thru the dash vents.


I've attached another pic of what I presume is a vacuum solenoid? Its about the size and shape of a roll of quarters with vac lines connected (and also brittle) . Any suggestions for a part number or replacement? Thanks again

 

What is the part number for the Dorman three way check valved, that worked ? There are several choices.

 

Dorman Two Port Check Valve part#: 47150

 

Thank you on behalf of all who may need one.

I just ordered on on Amazon. $6.40 and I get free shipping W/ my Amazon membership.

 

I’ve bought Dorman a few times.

The last one I bought was faulty right out of the box.

Went to Reilly and ordered the AC delco one for less cost and wayyyy better quality.

https://www.oreillyauto.com/detail/c...+valve+acdelco

learn from my mistake

 

Wouldn't surprise me one bit if both of em emerged from the same plastic mold in Shenzhen. Since AC Delco isn't a "manufacturer" anymore, only a name on a box, anything could happen, and probably does. They just buy from the cheeeeepest source that meets their specs ("Is it a vacuum check valve? Yup. Sounds good to me, ship it") just like everybody else does.

For example, here are the parking brake cables I put on one of my vehicles the other day.




I think you just got unlucky with the specific specimen of Dorman part you got. Odds are the same that an AC Delco one would have been bad. For the same vehicle in question, I ordered an AC Delco cam pos sensor in a batch with some other parts, and it turned out to be bad. Made it throw every kind of CPS code available and barely even ran. Ended up going down to the corner parts store and getting a Standard Ignition one, which works fine.

 

Ya, seems to be true for auto parts in general. I needed a cap and rotor last week for this car, my neighborhood chain Auto Parts store had a kit in stock. I bought it ,wisely looked at it after I got in my car at the store before I left. The rotor contact had uneven plating (and that's where it had plating, much of it was bare) and the underside had loose cellophane flapping on it. I took it back in the store, the counter clerk agreed it looked bad, she got the Mgr who looked at it, then he challenged me "what's wrong with it"? after I gave him a review of the issues, they gave me another rotor. However, given the seemingly scarcity of Gen III parts, I guess I should be glad there's something out there we can work with .

 

I had a similar situation and ended up calling a New Jersey chimney sweep, which made things way easier. They handled the cleaning and inspection in one go, and I liked that they shared photos and clear pricing before doing anything. The techs followed NFPA standards, so I felt confident everything was safe. Plus, catching minor issues early saved me from a bigger repair later.