Looking for vacuum valve

[Ben Bruce aka First Born]

Folks, the HVAC control on my 1992 Roadmaster is bad. It is a vacuum "distribution" valve.  Difficult to get to. Probably impossible to obtain. Operates the doors in the hvac module.

 

  I have an idea of a panel of small vacuum valves, similar to a switch panel. The valves don't have to be high tech.  Seems like I cant ask the correct question on the search engines.   Are they available?  

 

  Thanks

  Ben

[Bill Stoneberg]

Ben..  Have you tried Old Air Products in Dallas ?   They have actuators which is what the valves are called at least in the old cars.

 

Good luck as I am fighting the same thing.

 

 

[Ben Bruce aka First Born]

Thank you, Bill

  I think the actuators are ok. The problem is that the controller does not send the vacuum to the actuators. This is a "manual" system as opposed to an automatic system.  Looking for something to make it MORE manual.

 

  Ben

[NTX5467]

I presume you've already traced the vacuum line from the engine to the vacuum reservoir and then inside the car to the a/c control unit?  AND that you've got good vacuum through all of those things?  What is the "performance complaint"?

 

The actual vacuum "switch" is usually on the backside of the instrument panel control.  IF all the air you get is "floor and defrost", then it's usually a basic vacuum supply issue.  That's the default mode for "no vacuum", typically.

 

ARE you sure it runs off of vacuum?  That the actuators have a vacuum line going to them?  By that time, many manual hvacs were using stepper motor actuators to replace the vacuum units.

 

NTX5467

[Ben Bruce aka First Born]

Have done so, Willis. Hooked my AC vac pump to the "supply" line at the throttle body. I have vacuum to a distribution thing at the dash.  There is a "mode" lever in he control panel. This works a rotary valve/switch that sends  vacuum to the different actuators to move the various doors.  There is a temp lever in the same panel. It controls the door to the heater core.  The entire HVAC unit is contained in a module under the dash.

 

  I have vacuum in the supply line to the mode valve/switch. Moving the mode lever seems to make no difference.  The best I can interpret from the manual ,obviously written by an engineer, this condition requires replacing the mode valve/switch. Which requires dash disassembly. IF one can be found.

 

  I guess I have no alternative.

 

  Thanks

  Ben

[JohnD1956]

Is this what you were looking for?

https://www.google.com/aclk?sa=l&ai=DChcSEwj9w_Dp6q3dAhWHnLMKHdCuBn0YABAPGgJxbg&ae=1&sig=AOD64_2_cSPVqDFrMBc90iiBOJgXCDSwcA&ctype=5&q=&ved=0ahUKEwiI1evp6q3dAhWPjlkKHdNQBvcQwjwIUQ&adurl=https://www.ruralking.com/master-manufacturing-3-8-barb-x-3-8-barb-valve-pbv-38hb-csk%3Futm_medium%3Dcpc%26utm_source%3Dgoogle%26utm_campaign%3Dshopping%26utm_content%3D78130180%26gclid%3DCj0KCQjwidPcBRCGARIsALM--eNwl4E-_QlKw8PmKNO9yw0bgGA1By1xgyIT4IS0c3iy9BBvghU5GgEaAkYGEALw_wcB

[Ben Bruce aka First Born]

Thanks John. Might work. Present plan is to attempt replacing defective part. Whatever that may be!

 

  Ben

[NTX5467]

The rotary style of "switch" was used for many years, from the middle '60s or so.  Earlier ones were pot metal with the later ones being plastic.  The side with the vacuum supply rotates against the outlet side, all held together by a wide clip.  Yours' should be the plastic version.  Once the control head is removed, I suspect you can disassemble the item and check for wear, which might be a simple "wear" issue that can be repaired, cleaned, or similar.

 

Find an AC/Delco (auto supply) catalog, or similar, which is an "Illustrated listing" of each item and what it fits.  You'll be surprised at what has been used and where!  If the orig item can't be made to work, you might discover another one with a different mounting tang, that might be modified to work.  Many of these valves had common items, but with different mounts.  Just as blower motor switches were common, until you got to the lever and mounting flanges.

 

I presume you've already checked for vacuum at the end of the affected vacuum line and that the actuator responds to vacuum?

 

Just some thoughts,

NTX5467

[Ben Bruce aka First Born]

I have vacuum. Removed vac line at throttle body and hooked to vacuum pump.  Mode control seems to make no difference. Scenario is this.

   With mode lever in Max and temp lever in Heat ,  air blows heavy from dash vents.  When temp lever is moved toward COOL, air starts to go away. At full cool, almost no air from dash vents.  MODE lever, which is supposed to move vac valve makes no difference. 

  Really has me confused.  I will attempt removing the dash parts so I can see everything this next week.  I really want this car to be my Daily Driver, and sell the '95 PA. 

 

  Thanks

   Ben