1968 Deville No air from dash issue

[Pmartin2204]

Hello club. New member here. Have been reading posts for awhile and finally gave in I guess. So I recently purchased a 68 Deville 2 door hard top and I replaced the dash unit for the climate control, the master switch and relay as well as the power servo, have ordered an nos transducer as well. My question however is that I can get the blower to operate at low and high speeds when I operate the dash switch but the air only will come from the windshield and lower passenger kick panel and not the dash. I plan on buying a new diaphragm actuator for the kick panel as well as the one on the firewall and I believe there is another  the dash unit in the car next. Any advice would be appreciated.

[Pmartin2204]

The compressor is disconnected at the moment due to no freon in the system as well.

[cadillacmike68]

Welcome to the fora.

You replaced a lot of parts that might not have needed replacing. Was it doing anything at all before all the new parts?

The vacuum motor (it's called a motor) On the firewall, right under the power servo's "donut" is the one that changes from defroster vents to dash vents. The default operation is defroster vents. NO vacuum on this motor gets you defroster air flow. Vacuum pulling the door closed gets you dash (or lower heater) air flow.

First, you might have a vacuum leak - check Everything.

To test, you can apply vacuum to that round vacuum motor on the firewall while the system is running and see it if changes the air flow from the defroster vents to the dash.  Make sure you plug the disconnected vacuum line.

Also, if you have not already done so, get an original shop manual, readily available on ebay. I also strongly recommend you get Cadillac Tim's book on 1968 Climate Control. That book has helped me immensely with my 1968 DVC.

To check the operation of the transducer, and this is a good time to test with milder weather, set the system to AUTO and the temp dial to 65. Make sure it's warm enough like in a garage or outside in the sun. Look at the lever sticking out of the passenger side of the power servo, it should be all the way Out. Slide the temp dial to 85 while watching that lever. It SHOULD pull IN towards the main body of the power servo. If not, wither the big doughnut on the power servo is bad (but you just replaced this) OR the transducer is not functioning.  For the transducer No vacuum means full cold and Full vacuum means full heat. Another visual test is while it is in full heat (if it goes there), pull and hold the line closed on the big doughnut on the power servo and that lever out the back should extend - and the air should no longer blend in heat. Doesn't matter where the air is going, the heater blend door should kick in when on full heat. I could go on...

[chrisntam]

Welcome to the club & Cadillac ownership as well.

I have a '70, so I'm not much help.  Do you have a factory service manual?  There is a pretty good diagnosis chart in that manual that can likely help you.

Also, there's a member here, screen name is Cadillactim, he has a very good alternative manual to the FSM that he sells (he wrote it).  That manual takes you through testing, diagnosis and potential repair (if appropriate) of each component.  He sells his manual for around $40, IIRC.  I highly recommend it and the FSM as well.

Here's a link to his posts, you can send him a private message (pm) to inquire about how he can help you. He also sells a/c, cruise control and some electronic parts for our old cars.  On of his posts may have his phone number it it, a quick search did not reveal it.

http://forums.cadillaclasalleclub.org/index.php?action=profile;area=showposts;u=79

Others will chime in as well.

Welcome!  And don't be shy about posting questions, answers and pictures!

[Pmartin2204]

Thanks for the insight fellas. I do have the fsm which helped get a lot of the vacuum lines routed as the previous owner had things rerouted. When I got the car it didn't do anything as far as the climate control and blower motor operation. So I got the fsm and I believe I have the vacuum lines routed. Next I replaced the dash unit as I could see the amp was blown out visibly. Then I replaced the tugboat switch which was also torn and broken and replaced the relay while I was at it. Next I got a used power servo which was said to hold vacuum but I think I'll sand the rotary valve and vacuum grease it. So that could be an issue. Anyway mine was junk as the white clip was broken. But I didn't toss it for a good core. Anyway I am waiting on a nos transducer. So after I did all that I could get the fan to come on with the dash unit. And in the morning I'll fire it up and  see if my power servo does anything after trying your suggestion Mike. Thanks Chrisntam for the link  and for the tip on Cadillactim. I was hoping they were still around as i have read in the past they are a great parts source. Anyway I'll keep you posted.

[Pmartin2204]

So a little update. I installed a nos transducer and when I start the car and turn the climate switch to vent I can see the passenger side kick panel vent close but it slowly opens back up which indicates a vacuum leave I believe. I have one arriving in a few days. As far as getting any air to come from the dash vents i am going to say at the very least the vacuum motor mode door is inoperable. There is good vacuum to it but I don't believe the vacuum motor holds vacuum. I can hear the blower change speeds from low to high and when I operate ice and fog I can see the kick panel vent open and close slightly. So as of right now I will replace the vacuum motor and probably the heater core as it has a small leak since I'll have the heater box open. Thanks guys.

[Pmartin2204]

So I got the heater core replaced and the vacuum motor for the mode door replaced and now I can get air flow from the floor to the dash. Still need to look into a new power servo. I applied vacuum to it from the manifold, looked away for a minute for some reason or another and hear a loud pop and found the arm of the power servo had popped off. I reinstalled it along with the clip but not sure if I blew out the donut. Also need to make sure my transducer works as well. Just because it was a nos unit it still may not be functional. I do know however if I manually move the blend door to either driver or passenger side I can get hot or cold air. Anyway just a quick update. 

[cadillacmike68]

Apply vacuum to the port on the big donut.  If the arm pulls in and stays in, that part is still good.

The rotating valve might have worked loose inside.

[Pmartin2204]

Applied vacuum to the power servo and the arm pulls in. Looks like I have to check out the vacuum transducer next and the in dash sensor as well. Thanks for the help cadillacmike.

[cadillacmike68]

you're welcome.

If you haven't done so, get Cadillac Tim's Climate Control book for 1968. It helped me a lot.

[Pmartin2204]

Looks like my transducer is working along with my power servo. Now just have to see about adjusting the screw at the end of the power servo arm to hook on to the blend door arm. I'm not sure if someone swapped springs at one point. I'll try to attach a picture this evening of what I have going.

[cadillacmike68]

There is supposed to be a little c-nut type of fastener to hold the Power Servo arm onto the pin.

[Pmartin2204]

Thanks for the heads up mike. Looks like I have to get a clip the previous owners tossed it.