New to website from Golden Colorado- Hello Everyone

[GreenCabbie]

I have a 1992 Cab that I just painted and put a new top on. Also added a new windshield as well. She is coming together nicely. Kind of my hobby car. I love the way she drives. I have a question and maybe this isn't the right forum and someome could tell me where that forum might be.

Has anyone had problems with a/c not coming out of the central vents. I can only get hot hair out of the central vents ? What did you do?

I can get a/c out of the side vents but the manuals and websites say a/c should be coming out of the central vent as well.

Any help would be appreciated.

I tried to post a picture of my Cab but it didn't work . If anyone knows how to do that I would be thankful for some instructions.

[92 Drop Top]

Welcome !

I have a 92 as well, no A/C from the central vents either. I look forward to the answer.

As for pics, I added mine as files, there is a place to attach files with a "Browse" button next to it when you add a post. Be sure to click on "Add the file" when you pick one.

Cheers

[GreenCabbie]

Thanks for the help in posting a picture. On the air vent problem. Check out the discussion in the General Car Work Forum pg 5 of 7 there is a question from BigDaddy90Cabby who is "trying to get to the center vent servo?" The answer sounds really well described. I suspect this for could be an all day job since you have to take the entire dash off to get to the servo. I have had my dash off before and maybe it will be easier this time. I think the time would be worth it to get the cool air coming from the central vent. Good Luck.

[Briano1234]

Yes a vacuum leak or a BAD SERVO causes that condition.

where is the bad servo, under the dash.


And that thread says it all.

To post pictures you have to have a "photobucket" type of account, you upload your pictures there, then you post the link that says

[CalAltaDubber]

Hello Green Cabby and welcome to TRF.

Since I don't have AC in my cars I can't help you directly, but if you check http://www.cabby-info.com you might find that Kamy has something there to help you.

Best way to post pictures is first to have your picture loaded to the internet, Photobucket is a good choice or if you have some web space with your provider is another. When you are typing your post, use the Img button and a set of tags will appear. just put the web address for your picture between the two tags It should look something like this (I removed the first bracket so you can see the tags)
img]http://www.picture_address/picture.jpg[/img]
Again welcome and hope to see your car soon

[GreenCabbie]

Thanks for all the help. I'll try loading some pictures.

But Briano I loved your post in the General Car Work responding to " Trying to get to the center servo" . Since I have the same problem. And it sounded so easy so I started trying to get to my center servo in my 1992 VW Cab. I removed the radio, htr, and gauges are out . I was able to remove 2 screws on the outside by the doors holding the ends of the dash. Also the front of the dash by the windshield is loose.
It feels like it is ready to come out. But the middle section by radio feels like it screwed down. I don't know if I have to take out the white bench that goes all the way across the dash to access any additional screws or not. Or even how to take out the white bench?

Can you give me further instructions on how to remove the dash including the white bench if I need to.

Thanks,
GreenCabbie

[kamzcab86]

First, welcome!

Second, in order to replace the center vent servo, you must remove the dash (don't bother trying to do it without removing the dash ~ been there, done that ), which requires removing the kneebar*: http://www.cabby-info.com/Files/DashRemoval.pdf .

Third, bookmark this site: http://www.cabby-info.com/index.htm . The answers to most of your questions are there. Specifically, the problem you mention: http://www.cabby-info.com/hvac.htm#Only_Heated . There is a difference between "no air" and "only heated air" exiting the center vent. So, if air is coming out of the center vent, but it's not cold air (when the A/C is on), replacing the servo won't solve the problem.


*Kneebar is the proper term for it, not "bench". Some folks leave out the connector screws along the top of the kneebar when reinstalling for future ease of dash removal.

[GreenCabbie]

Thanks for the help Kamzcab86. You know I was all over the cabby-info website before I found this Topless Rabbit Forum . The two together have been a huge help. I am with you on how come I can get heated air out of the center vent but not cool air. I studied the flow graphics for all the vents and the air controls distribution diagram on the cabby-info website. And something is off.

Cabby-info stated it could be a servo. Not knowing where else to go I am headed there to eliminate that possibility first.

Since cool air , really cool air comes out of the side vents I am thinking the a/c unit is ok.

Do you know how to remove the kneebar? ( thanks for the correction of the bench labeling by myself)

This job is a tough one,

[Briano1234]

Thanks for the help Kamzcab86. You know I was all over the cabby-info website before I found this Topless Rabbit Forum . The two together have been a huge help. I am with you on how come I can get heated air out of the center vent but not cool air. I studied the flow graphics for all the vents and the air controls distribution diagram on the cabby-info website. And something is off.

Cabby-info stated it could be a servo. Not knowing where else to go I am headed there to eliminate that possibility first.

Since cool air , really cool air comes out of the side vents I am thinking the a/c unit is ok.

Do you know how to remove the kneebar? ( thanks for the correction of the bench labeling by myself)

This job is a tough one,

Well the issue is:....... you have air flow out the center vent....


Heater Valve isn't shutting the flow of water through the core.
No dash removal required.

Replace the heater control valve or make sure that it is all the way off.

Engine bay drivers side to the left of the brake booster.

If fully off, it still will trickle some coolant, but the a/c can over come it and blow out cold.

[GreenCabbie]

I checked out the heater control valve and when it is completely off there is no hot air coming through the center vent when the ac or cool air is selected. When I select heat and check the heater control valve it is in the open position and hot air flows generously out of the center vent. So the heater control valve seems to be working.

When I select full ac there is a whisper of a flow that is somewhat cool out of the center vent but not near the flow when the heater control valve is blowing hot air. It is like the cool air is blocked somewhere. Is there a flap in the blower box that could be stuck? I am guessing but I thought it might be a servo to check first.

What makes me think it is the distribution system somewhere and not an ac problem is the side vents ac works fine.

I now have the dash and kneebar off so hopefully I have access to all I need to check. Any further advice is appreciated.

Where would I find the vaccum pressures to test the servos. Are they all the same pressure . I have a vaccum tester. Plan to test all of the servos tomorrow. Also plan to put a supply vaccum on the HVAC selector to see if each position works and the servo works at each location.

Again thanks for the help.

[Briano1234]

I checked out the heater control valve and when it is completely off there is no hot air coming through the center vent when the ac or cool air is selected. When I select heat and check the heater control valve it is in the open position and hot air flows generously out of the center vent. So the heater control valve seems to be working.

When I select full ac there is a whisper of a flow that is somewhat cool out of the center vent but not near the flow when the heater control valve is blowing hot air. It is like the cool air is blocked somewhere. Is there a flap in the blower box that could be stuck? I am guessing but I thought it might be a servo to check first.

What makes me think it is the distribution system somewhere and not an ac problem is the side vents ac works fine.

I now have the dash and kneebar off so hopefully I have access to all I need to check. Any further advice is appreciated.

Where would I find the vaccum pressures to test the servos. Are they all the same pressure . I have a vaccum tester. Plan to test all of the servos tomorrow. Also plan to put a supply vaccum on the HVAC selector to see if each position works and the servo works at each location.

Again thanks for the help.

There is no valve or flapper save for the center/defrost one that controls the cooling.
It could be that you have some debris in the way.


here are the dash vents.





For vacuum you have to pull enough with a mighty vac.
you can see the internals here:
http://www.cabby-info.com/Files/AddingH ... eVents.pdf

There is the one flap that controls the foot well that may be an issue but if you get heat out the center, then you should get cool air out.

Now the side vents give raw air, that is air a/c or fresh that doesn't go over the heater core.

If the heater valve isn't fully at the off stop but slightly cracked open it will produce enough heat to over come the a/c in the center.
Heater Valves do go bad internally, where the arm moves but the center roller doesn't.

The side vents are about 10 degrees cooler than the center vents normally.

[GreenCabbie]

Thanks for the diagrams and the link. Explained alot .Good idea on the debris it could be the culprit. Even harder to get to based on the exploded views. Would it most likely be past the fan and built up on the evaporator?

I have a hand vacuum pump that I was going to use to test the servos. If I connect the vacuum pump to the supply port of the vacuum distributor and move the control selection lever. Shouldn't each of the servos be activated and hold their new position? Including the central vent servo.

The flap for the central vent is closed and feels really stiff to move. I tried to push on it but it would not budge. Must be restricted by the cable or servo.

If the servos check out I'll start looking for debris. I guess that means taking the blower box apart?? Or do you know a better way?

Any other thoughts are always appreciated.

[Briano1234]

If you don't have a debris guard on the hood vents, then depending on if you have a screen over the fresh air plenum then debris can enter the system.

If your fresh air plenum don't have the screen, then you may want to add one or get a plenum out of a later cabby.
The Debris guard is in the General car work catagory...

Yes pulling suction with a mighty-vac should operate all the servo's nicely, as that is how I do it.

If the heat or non-heated air comes out fast, then it isn't debris that is the problem.
If the air is chilled from the side vents, then it may be that you need to charge your system.

Don't discount a broken heater valve as that is usually the issue. As under defrost you get a/c air with heat, and with the slider you can get any level of a/c with heat.

[GreenCabbie]

I went out and purchased a Mityvac vacuum handpump today. I was wasting alot of time with the other one I had only to find out it wouldn't hold a vacuum. What a great vacuum handpump. Thanks for that.

Couple of questions if you don't mind. The servo that is on the left side of the radio that is the footwell vent servo. When I hooked the Mityvac up to each line directly from the Mityvac to servo. There are two lines to this servo and neither held a vacuum. I am assuming one vacuum line holds it in the defrost position and one holds it in the vent position. I am assuming this a bad servo.

The same was true with the Center vent defrost servo. Wouldn't hold a vacuum as well. So do you know where I might find these servos to purchase? I assume this is the center vent I am trying to get air out of .. correct?

Since I was in the mood to continue I decided to test the Vacuum distributor so I blocked all the outputs and added 18 in Hg vac to the supply port and it held...... so at least one component is good.

I'll check the air recirculation servo tomorrow and hopefully it will be good.

I really appreciate you help on this as this has been a learning curve for me but I feel I am almost there in getting this fixed. I'm thinking if I replace the bad servos and even the heater control valve I could be in good shape. Beside the challenge of putting it back together.

Thanks again

[Briano1234]

The center vent servo it on the right side of the heater box. It is the only one that requires dash removal for replacement.
The one on the drivers side is the one used to control "bi" level, that is foot area cool or heat.
It is a dual servo, and I have never seen them go bad personally.

The defrost/center servo is the same one that is one the outside of the heater, on the fresh air/recirc flapper control.


You can usually find them in a wrecking yard, They were used on quite a few VW's mk1's and Golfs.
If you find a "metal" canned one they usually are good and rarely are bad. I usually pull the metal ones off the cars in the yard that I find.


The best way to pull a vacuum that I have found is to connect the "egg" crate or balls under the hood to the air intake, and with the "T" connector under the hood.

You hook the balls in line with the vacuum distributor, and then suck it down as low , ok high of a reading that you can get. Then you use the heater controls to cycle between the servos to see if they are working. The Foot well servo is a little different and it uses Vacuum to open or close it if I remember right.

The Center/defrost servo is home or rest and air comes out the defrost only.
The center vent is on the Full out/or bi-level.

The foot well is Bi-level, and floor only.

I have also gone as far as to install a a/c cut-out switch on the dash, so I can have non-a/c air in defrost as well as any position I choose.

To do that I moved the wires off the switch on the passenger side of the heater controls to a on/off switch that I installed on the dash blanks.
viewtopic.php?f=27&t=2036

Debris guards can be found on some rabbits and Sirocco's .
There are 2 spring clips that hold it in place, but never fear you can make one:

viewtopic.php?f=27&t=1509