HELP ⚠️🌡️HVAC Problems HELP 🆘 PLZ‼️

602gbody

Not-quite-so-new-guy
May 13, 2020
34
8
Phoenix
1984 Buick Regal I'm trying to get Air to blow thru my top vents & get my blower motor to work on highest setting.
so far from what I read the vents are controlled by vacuum from the carburetor ? (Not sure) And I'm supposed to have a vacuum tank (black ball) mounted to my HVAC box ? (Again not sure) I have a vacuum ball mounted by the driver side headlight from what I read this is for cruise control not HVAC I don't have one on my HVAC Box.

I found a vacuum diagram on here somewhere (see attached pictures) and from what I understand I'm looking for a white & violet colored vacuum line coming from the inside of the car out by the passenger fender side and going into the vacuum tank.

As far as the blower motor issue I've replaced the resistor and relay so I'm guessing the blower motor itself needs to be replaced since it's not working on the highest setting?

I found what I think is the heater control valve with a white line connected to it is that my white line I'm looking for?

One last thing I read that there's a red wire leading to the starter motor that needs to be connected in order to get the blower motor to kick on in highest setting is that right?
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57 Handyman

Greasemonkey
Feb 6, 2017
158
43
Here are a couple of tips on resolving HVAC problems on 5th Gen G-bodies which I can contribute and hopefully will help. My 5th Gen is an 87 El Camino so some of the parts may be a little different but the functionality and schematics should be similar and apply.

1. The resistor is the electrical control for fan speeds. Since you've replaced both the resistor and the relay and have not resolved the high speed fan problem, you need to run a test on the motor itself. In order to test for the highest speed, run 12v directly to the fan via the single wire on top and by having the fan body grounded to the negative side of the battery. If the fan does not run full blast, then replace the motor.
2. Make sure you have a good vacuum source attached and goes to your HVAC control panel inside the vehicle. Yes, the carb and vacuum ball provide the continuous source.
3. The vacuum connects to the control panel thru the purple plastic hose via the passenger's side harness below the AC housing. The beige broken hose in your picture goes from the control panel BACK TO the hot water control valve near your heater. I believe the valve is in the last picture you've posted.
4. You should use a vacuum pump to help troubleshoot vacuum operational functions. I prefer to troubleshoot vacuum issues with a pump that I know works and so opted to buy one. However, you can probably borrow a vacuum pump from Autozone.
5. Start tracing backwards from the carb-to-ball-to-control panel and making sure there aren't leaks. If you find leaks or broken plastic tubing, a good substitute/replacement is black plastic tubing sold at parts stores for air bag applications. Also, the best way to connect good/new tubing with old/broken lines is to use rubber vacuum hose that is available at auto parts stores. I found both of these at NAPA.
6. Once you've established good vacuum up to the control panel, you'll have to verify by testing that each of the vacuum diaphragms are functioning properly. There are 3 or 4 diaphragms that control the airflow by opening and closing doors/pathways in the AC box. This is tedious work but necessary to locate the problems with airflow in the cabin.
7. Unfortunately, the diaphragm which directs airflow between the top vents/defroster and down-to-the-floor is the hardest to replace. In order to correct this, your options are: (1) to cut the plastic ducting (which is marked) to gain access to the nuts inside OR (2) to pull this part of the air handler out from under the dash.

Good luck!
 
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602gbody

Not-quite-so-new-guy
Thread starter
May 13, 2020
34
8
Phoenix
Here are a couple of tips on resolving HVAC problems on 5th Gen G-bodies which I can contribute and hopefully will help. My 5th Gen is an 87 El Camino so some of the parts may be a little different but the functionality and schematics should be similar and apply.

1. The resistor is the electrical control for fan speeds. Since you've replaced both the resistor and the relay and have not resolved the high speed fan problem, you need to run a test on the motor itself. In order to test for the highest speed, run 12v directly to the fan via the single wire on top and by having the fan body grounded to the negative side of the battery. If the fan does not run full blast, then replace the motor.
2. Make sure you have a good vacuum source attached and goes to your HVAC control panel inside the vehicle. Yes, the carb and vacuum ball provide the continuous source.
3. The vacuum connects to the control panel thru the purple plastic hose via the passenger's side harness below the AC housing. The beige broken hose in your picture goes from the control panel BACK TO the hot water control valve near your heater. I believe the valve is in the last picture you've posted.
4. You should use a vacuum pump to help troubleshoot vacuum operational functions. I prefer to troubleshoot vacuum issues with a pump that I know works and so opted to buy one. However, you can probably borrow a vacuum pump from Autozone.
5. Start tracing backwards from the carb-to-ball-to-control panel and making sure there aren't leaks. If you find leaks or broken plastic tubing, a good substitute/replacement is black plastic tubing sold at parts stores for air bag applications. Also, the best way to connect good/new tubing with old/broken lines is to use rubber vacuum hose that is available at auto parts stores. I found both of these at NAPA.
6. Once you've established good vacuum up to the control panel, you'll have to verify by testing that each of the vacuum diaphragms are functioning properly. There are 3 or 4 diaphragms that control the airflow by opening and closing doors/pathways in the AC box. This is tedious work but necessary to locate the problems with airflow in the cabin.
7. Unfortunately, the diaphragm which directs airflow between the top vents/defroster and down-to-the-floor is the hardest to replace. In order to correct this, your options are: (1) to cut the plastic ducting (which is marked) to gain access to the nuts inside OR (2) to pull this part of the air handler out from under the dash.

Good luck!
Thank you sir I appreciate your response I'm about to test out the blower motor fan as you mentioned.
I'm gonna have to source a vacuum tank my car doesn't have it anymore.

Funny you mentioned the diaphragms I was just watching a video some guy was testing each one out with a hand held vaccum pump & said the exact same thing that was the most expensive and hard to come by part.

I'm gonna see if I can borrow a vacuum pump if not I'll buy one at this point I don't care and I'm determined to get this HVAC system restored.

Thank you for mentioning what type of tubing I'll be needing that was gonna be one of my follow up questions.
 

602gbody

Not-quite-so-new-guy
Thread starter
May 13, 2020
34
8
Phoenix
So far I've replaced the Relay with part with part number RY20 from O'Reilly's the blower motor with part number PM140 from O'Reilly's and the blower motor resistor with part number 973-032 from O'Reilly's...

I also removed the speed switch and cleaned all the contacts (seen it on a YouTube video)


Still the highest setting on the blower isn't working....
 

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602gbody

Not-quite-so-new-guy
Thread starter
May 13, 2020
34
8
Phoenix
At 9:00 time mark he mentions an orange wire that sends a signal coming from the blower motor speed selector to the relay might be my problem ?

 

602gbody

Not-quite-so-new-guy
Thread starter
May 13, 2020
34
8
Phoenix
🤔
 

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L92 OLDS

Royal Smart Person
Mar 30, 2012
2,496
113
West Michigan
You’re throwing a lot of new parts at it. Did you check your fusible link to make sure you have power for high fan? There are two fusible links down by your starter that provide power for the entire electrical system. When one of them blows it cuts power to the high fan circuit. This is a common problem on G body cars.
 
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