Ac clutch engages on defrost and not dash - First Generation Pontiac Firebird (1967 - 1969) - Firebird Nation

Jump to content


FirebirdNation.com is the premier Pontiac Firebird forum on the internet. Supporting Members do not see the above ads.
Photo
- - - - -

Ac clutch engages on defrost and not dash


  • Please log in to reply
17 replies to this topic

#1 Birdstein

Birdstein

    Firebird Newbie

  • Full Member
  • Pip
  • 10 posts
  • Gender:Male
  • First Name:Chris
  • City:Saint Marys
  • State or Province:GA
  • Country:USA
  • Interests:Muscle cars, Sports Memorabilia
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 383 stroker
  • Transmission: Turbo 350

Posted 3 weeks ago

I have a 1968 pontiac firebird. The ac works good, but only when selector switch is turned to defrost. I want it to blow cold air when selector switch is on dash. I put on a EFI system and maybe crossed some wires somewhere. Maybe heater control switch. I have a horton Heater control valve 46115vuh. there are two male spade terminals. If I have the wrong one grounded could this cause my problem.



#2 sea dog

sea dog

    Firebird Master Tech.

  • Administrator
  • 2979 posts
  • Gender:Male
  • First Name:Robert
  • City:Fruitland Park
  • State or Province:FL
  • Country:USA
  • Interests:cars, guitars, women, firearms,
  • Year: 1995
  • Make: Pontiac
  • Model: transam
  • Engine: 5.7 lt1
  • Transmission: 4l60e

Posted 3 weeks ago

AC control unit uses vacuum to control what passage ac goes to. The most common problem is a vacuum line or lines are leaking or have become disconnected from control unit.

 

Also the control unit can break down.

 

If you'll go to 1st gen tech section. Then hit master index at top, new page will open with 69 Pontiac service manual. It should have vacuum diagram of ac control unit. Plus other info on ac system.



#3 Birdstein

Birdstein

    Firebird Newbie

  • Full Member
  • Pip
  • 10 posts
  • Gender:Male
  • First Name:Chris
  • City:Saint Marys
  • State or Province:GA
  • Country:USA
  • Interests:Muscle cars, Sports Memorabilia
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 383 stroker
  • Transmission: Turbo 350

Posted 3 weeks ago

Thank you I downloaded the diagrams. I will go thru them. I looked for a vacuum line coming thru the firewall to connect to engine somewhere. Have not found one yet.  I will get under dash on passenger side a look for something. It probably is a vacuum. 



#4 fourthirteen

fourthirteen

    Firebird Tire Changer

  • Full Member
  • PipPip
  • 55 posts
  • Gender:Male
  • First Name:B
  • City:East
  • State or Province:TN
  • Country:USA
  • Year: 1967
  • Make: Pontiac
  • Model: See the above photo
  • Engine: 400
  • Transmission: Manual, 4-speed, Muncie

Posted 3 weeks ago

Your subject line says “Ac clutch engages on defrost and not dash”...does this mean the compressor clutch doesn’t engage when the dash vents are selected? If so then it’s an electrical problem. I don’t know the answer but I think that you need to be looking at electrical issues and not vacuum issues as vacuum is used to actuate the duct dampers, not to actuate the AC compressor clutch...that’s electrical.

#5 Birdstein

Birdstein

    Firebird Newbie

  • Full Member
  • Pip
  • 10 posts
  • Gender:Male
  • First Name:Chris
  • City:Saint Marys
  • State or Province:GA
  • Country:USA
  • Interests:Muscle cars, Sports Memorabilia
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 383 stroker
  • Transmission: Turbo 350

Posted 3 weeks ago

Yes clutch engages on defrost and blows cold air to defrost vents, but when I have selector switch to vent the compressor disengages. Of course other selectors are on Hi and cold.  Do you think I have power and ground switched on horton Heater control valve 46115vuh.  What would happen if I switched the wires on that solenoid. And I cannot find any vacuum lines on my ac control unit. I am not sure my unit is factory. DO all units have vacuum lines coming off of them.    Thanks for the help. I really appreciate it.



#6 sea dog

sea dog

    Firebird Master Tech.

  • Administrator
  • 2979 posts
  • Gender:Male
  • First Name:Robert
  • City:Fruitland Park
  • State or Province:FL
  • Country:USA
  • Interests:cars, guitars, women, firearms,
  • Year: 1995
  • Make: Pontiac
  • Model: transam
  • Engine: 5.7 lt1
  • Transmission: 4l60e

Posted 3 weeks ago

GM is a big believer in vacuum control. But on many aftermatket units, it's either electric or cable control

 

When you say you switch to vent, are you switching ac control to the vent setting? If yes, this turns off compressor and only fan runs. Ac compressor runs in ac, mak, & bi-level modes.



#7 Birdstein

Birdstein

    Firebird Newbie

  • Full Member
  • Pip
  • 10 posts
  • Gender:Male
  • First Name:Chris
  • City:Saint Marys
  • State or Province:GA
  • Country:USA
  • Interests:Muscle cars, Sports Memorabilia
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 383 stroker
  • Transmission: Turbo 350

Posted 3 weeks ago

R561167.JPG

 

 

 

 

 

This is unit I have. has electronic not vacuum hose.   I will post picture of my heater control system later, but top lever says fan; left is off and right is HI, Middle lever is cold left hot right and bottom lever is vent left defrost right. 



#8 fourthirteen

fourthirteen

    Firebird Tire Changer

  • Full Member
  • PipPip
  • 55 posts
  • Gender:Male
  • First Name:B
  • City:East
  • State or Province:TN
  • Country:USA
  • Year: 1967
  • Make: Pontiac
  • Model: See the above photo
  • Engine: 400
  • Transmission: Manual, 4-speed, Muncie

Posted 3 weeks ago

So its an aftermarket system? Are you using the non-A/C factory controls that look like this? If so then how do you turn the A/C on...is there an aftermarket A/C button that you push? If no aftermarket button then whoever installed it must have decided to use the Defrost setting to trigger the A/C compressor clutch, although Im not sure how you would do that.
I still dont know the answer but some things are becoming more clear now.
Well get there.

Attached Files


Edited by fourthirteen, 3 weeks ago.


#9 Birdstein

Birdstein

    Firebird Newbie

  • Full Member
  • Pip
  • 10 posts
  • Gender:Male
  • First Name:Chris
  • City:Saint Marys
  • State or Province:GA
  • Country:USA
  • Interests:Muscle cars, Sports Memorabilia
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 383 stroker
  • Transmission: Turbo 350

Posted 3 weeks ago

Don't know if this information helps, but when the middle lever is full cold I have 12v to heater control valve wire. When I begin to move it towards heat I lose 12 volts to heater control valve wire. If wires are hooked up right I assume it opens the valve and sends water to heater core. When that happens does it send a signal to AC compressor to do something?



#10 Birdstein

Birdstein

    Firebird Newbie

  • Full Member
  • Pip
  • 10 posts
  • Gender:Male
  • First Name:Chris
  • City:Saint Marys
  • State or Province:GA
  • Country:USA
  • Interests:Muscle cars, Sports Memorabilia
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 383 stroker
  • Transmission: Turbo 350

Posted 3 weeks ago

This is a picture of my control panel

 

 

 

 


Edited by Birdstein, 3 weeks ago.


#11 Birdstein

Birdstein

    Firebird Newbie

  • Full Member
  • Pip
  • 10 posts
  • Gender:Male
  • First Name:Chris
  • City:Saint Marys
  • State or Province:GA
  • Country:USA
  • Interests:Muscle cars, Sports Memorabilia
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 383 stroker
  • Transmission: Turbo 350

Posted 3 weeks ago


Edited by Birdstein, 3 weeks ago.


#12 sea dog

sea dog

    Firebird Master Tech.

  • Administrator
  • 2979 posts
  • Gender:Male
  • First Name:Robert
  • City:Fruitland Park
  • State or Province:FL
  • Country:USA
  • Interests:cars, guitars, women, firearms,
  • Year: 1995
  • Make: Pontiac
  • Model: transam
  • Engine: 5.7 lt1
  • Transmission: 4l60e

Posted 3 weeks ago

Ah yes, the invisible control unit



#13 Birdstein

Birdstein

    Firebird Newbie

  • Full Member
  • Pip
  • 10 posts
  • Gender:Male
  • First Name:Chris
  • City:Saint Marys
  • State or Province:GA
  • Country:USA
  • Interests:Muscle cars, Sports Memorabilia
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 383 stroker
  • Transmission: Turbo 350

Posted 3 weeks ago

Attached File  heater.jpg   121.39KB   0 downloads Sorry can't get it to attach and show up


Edited by Birdstein, 3 weeks ago.


#14 fourthirteen

fourthirteen

    Firebird Tire Changer

  • Full Member
  • PipPip
  • 55 posts
  • Gender:Male
  • First Name:B
  • City:East
  • State or Province:TN
  • Country:USA
  • Year: 1967
  • Make: Pontiac
  • Model: See the above photo
  • Engine: 400
  • Transmission: Manual, 4-speed, Muncie

Posted 3 weeks ago

www.vintageair.com has the installation and operating instructions for your unit, as well as wiring diagrams. It says compressor should engage when temp lever is pushed to full cold position, and you should be able to direct the cold air to any of the three locations (dash, floor, or defrost). Heat is actuated when temp lever pushed full hot. So I’d think that you should have 12v to heater valve in “Hot” and 12v to compressor relay in “Cold”. I don’t understand why compressor only runs in Def position.
May want go through the lever calibration exercise they describe.
I’d post link but these are downloads I’m looking at from their website.

#15 Birdstein

Birdstein

    Firebird Newbie

  • Full Member
  • Pip
  • 10 posts
  • Gender:Male
  • First Name:Chris
  • City:Saint Marys
  • State or Province:GA
  • Country:USA
  • Interests:Muscle cars, Sports Memorabilia
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 383 stroker
  • Transmission: Turbo 350

Posted 3 weeks ago

Thank you found calibration instructions. https://www.vintagea..._pdf/473047.pdf    Will give it a try and respond back.



#16 Birdstein

Birdstein

    Firebird Newbie

  • Full Member
  • Pip
  • 10 posts
  • Gender:Male
  • First Name:Chris
  • City:Saint Marys
  • State or Province:GA
  • Country:USA
  • Interests:Muscle cars, Sports Memorabilia
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 383 stroker
  • Transmission: Turbo 350

Posted 3 weeks ago

:rockindude: Thank you very much. That calibration was the key. First it didn't work, but something different happened, so instead of having only one lever in beginning when calibrating, I had all three to the left then two back to the right for calibration. Cold and hot air when and where it is supposed to be. Again Thank you.



#17 sea dog

sea dog

    Firebird Master Tech.

  • Administrator
  • 2979 posts
  • Gender:Male
  • First Name:Robert
  • City:Fruitland Park
  • State or Province:FL
  • Country:USA
  • Interests:cars, guitars, women, firearms,
  • Year: 1995
  • Make: Pontiac
  • Model: transam
  • Engine: 5.7 lt1
  • Transmission: 4l60e

Posted 3 weeks ago

Even us old timers learn something new every day at the firebird nation.



#18 fourthirteen

fourthirteen

    Firebird Tire Changer

  • Full Member
  • PipPip
  • 55 posts
  • Gender:Male
  • First Name:B
  • City:East
  • State or Province:TN
  • Country:USA
  • Year: 1967
  • Make: Pontiac
  • Model: See the above photo
  • Engine: 400
  • Transmission: Manual, 4-speed, Muncie

Posted 3 weeks ago

Great! Thanks for the update.




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users