HVAC Issue: Diagnosis?
Thread Starter
Safety Car
Joined: Dec 2001
Posts: 4,295
Likes: 2
From: Indianapolis Indiana
Cruise-In III Veteran
Cruise-In IV Veteran
HVAC Issue: Diagnosis?
Issue: Weak heating/cooling on driver side, and NO heating/cooling (but blows air) on passenger side.
Onset: Doing a motor swap I briefly cracked a line open thinking I had to remove compressor. Line did not lose all pressure, just a few seconds. It has been this way since the swap.
Codes: None
Repair Attempt: I put my gauges on it and pumped in some R134a until the pressures were correct. The situation only improved minimally.
Ideas?
Onset: Doing a motor swap I briefly cracked a line open thinking I had to remove compressor. Line did not lose all pressure, just a few seconds. It has been this way since the swap.
Codes: None
Repair Attempt: I put my gauges on it and pumped in some R134a until the pressures were correct. The situation only improved minimally.
Ideas?
Last edited by BQuicksilver; Dec 19, 2013 at 11:34 PM.
Melting Slicks
Joined: May 2008
Posts: 2,606
Likes: 355
From: Rochester New York
Have you performed a full A/C evacuation and recharge?
Do you have manual or automatic HVAC controls?
There is a vacuum line that goes to the passenger side of the engine compartment under neath the battery. Easier to access it from the wheel well. I've seen these break, causing HVAC temperature/door problems. I think this is only if you have a manual HVAC controller.
Do you have manual or automatic HVAC controls?
There is a vacuum line that goes to the passenger side of the engine compartment under neath the battery. Easier to access it from the wheel well. I've seen these break, causing HVAC temperature/door problems. I think this is only if you have a manual HVAC controller.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Our AC system is VERY sensitive to proper R-134 pressures. The Service manual is VERY specific on operating pressures and has a procedure and detailed graph on pressure High Side & Low Side at various temperatures and humidity levels at a set RPM. Get a set of gages and obtain that chart. Knowing the high and low side pressures and help you pin point issues like low pressure, clogged orifice tubes excessive oil, etc…
You need a FULL SET of gages to monitor those pressures on both sides to get the unit to work correctly.
Can you switch the vent outputs to all the different levels Defrost, upper vents, lower vents, switch from recirc to fresh air??
OR
Does the air flow from all the vents and you are unable to command the changes. If that’s the case, you’re missing the reference vacuum line on the back of the intake manifold or you have a damaged vacuum tube. In the picture you can see the thin nylon vacuum line with the 90 deg boot. It is very short and pops off the vacuum
You need a FULL SET of gages to monitor those pressures on both sides to get the unit to work correctly.
Can you switch the vent outputs to all the different levels Defrost, upper vents, lower vents, switch from recirc to fresh air??
OR
Does the air flow from all the vents and you are unable to command the changes. If that’s the case, you’re missing the reference vacuum line on the back of the intake manifold or you have a damaged vacuum tube. In the picture you can see the thin nylon vacuum line with the 90 deg boot. It is very short and pops off the vacuum
Thread Starter
Safety Car
Joined: Dec 2001
Posts: 4,295
Likes: 2
From: Indianapolis Indiana
Cruise-In III Veteran
Cruise-In IV Veteran
n8dogg: No, I haven't done a full overhaul. Would prefer to diagnose what is up with the heat only on driver side before I fully recharge then realize I have some actuator issue as the main problem.
I have the automatic HVAC controls.
I'd be interested in seeing a shot of that vac line, just to be sure. My headers love to melt things.
I have the automatic HVAC controls.
I'd be interested in seeing a shot of that vac line, just to be sure. My headers love to melt things.
Thread Starter
Safety Car
Joined: Dec 2001
Posts: 4,295
Likes: 2
From: Indianapolis Indiana
Cruise-In III Veteran
Cruise-In IV Veteran
Bill: I have that $70 HF set of gauges. They're well-reviewed and seem to be one of HF's better tools.
What would I see with a clogged orifice tube or accumulator issue? I purchased both, but would rather not vac it down and open it up until I have a good theory on why the air only works for the driver.
I'm pretty sure recirc and the defrost work, but haven't tried the others. Will report back.
YES!! The air flows but I cannot command temps only in pass side. When I pulled the mani that little vac line was off without me pulling it. I could have just pulled it loose on accident during removal, but I'm suspicious it was off before now that you say this.
What would I see with a clogged orifice tube or accumulator issue? I purchased both, but would rather not vac it down and open it up until I have a good theory on why the air only works for the driver.
I'm pretty sure recirc and the defrost work, but haven't tried the others. Will report back.
YES!! The air flows but I cannot command temps only in pass side. When I pulled the mani that little vac line was off without me pulling it. I could have just pulled it loose on accident during removal, but I'm suspicious it was off before now that you say this.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
That Nylon line is inside the main wiring harness that runs from behind the engine to the PCM. If you look closely behind the passengers head, you can see where it enters the harness. You have to look in the passengers fender well to see where it comes out.
The DOES NOT like heat or battery acid!!!!!!!!!!!!!!! Acid eats it up like butter.
I made mine longer for ease of reinstallation and to fit better on my FAST 90 intake:
VACUUM RESIVOUR
The DOES NOT like heat or battery acid!!!!!!!!!!!!!!! Acid eats it up like butter.
I made mine longer for ease of reinstallation and to fit better on my FAST 90 intake:
VACUUM RESIVOUR
Thread Starter
Safety Car
Joined: Dec 2001
Posts: 4,295
Likes: 2
From: Indianapolis Indiana
Cruise-In III Veteran
Cruise-In IV Veteran
Bill, I just want a collection of all your secret views inside our cars, hehe.
I will have to reinstall that manifold and report back, but wouldn't we expect a code if the vacuum reference was off?
I will have to reinstall that manifold and report back, but wouldn't we expect a code if the vacuum reference was off?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Thread Starter
Safety Car
Joined: Dec 2001
Posts: 4,295
Likes: 2
From: Indianapolis Indiana
Cruise-In III Veteran
Cruise-In IV Veteran
Certainly a possibility. Would air cause the system to only work on one side? The pressures were correct after charging with reference to the chart on charge pressures vs temp, but the system still only adjusts on the driver side.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
How are you reading the DTCs??? If you use the DIC Built in code reader, it will show you actuator DTCs if the actuators are not responding.
They are B-0361, 0363, 0365, 0367, 0441, 0446.
NO,, the detached HVAC Vacuum reff line will not throw a DTC.
IF,, you have the DTCs and clear them, the actuators should cycle full range and then return to what the **** is set to.
If you listen to the center vent you can usually hear them cycle.
You can also pull fuse #25 and that will reset the controler and it should cycle also.
Bill
They are B-0361, 0363, 0365, 0367, 0441, 0446.
NO,, the detached HVAC Vacuum reff line will not throw a DTC.
IF,, you have the DTCs and clear them, the actuators should cycle full range and then return to what the **** is set to.
If you listen to the center vent you can usually hear them cycle.
You can also pull fuse #25 and that will reset the controler and it should cycle also.
Bill
Instructor
Joined: Mar 2010
Posts: 135
Likes: 1
Issue: Weak heating/cooling on driver side, and NO heating/cooling (but blows air) on passenger side.
Onset: Doing a motor swap I briefly cracked a line open thinking I had to remove compressor. Line did not lose all pressure, just a few seconds. It has been this way since the swap.
Codes: None
Repair Attempt: I put my gauges on it and pumped in some R134a until the pressures were correct. The situation only improved minimally.
Ideas?
Onset: Doing a motor swap I briefly cracked a line open thinking I had to remove compressor. Line did not lose all pressure, just a few seconds. It has been this way since the swap.
Codes: None
Repair Attempt: I put my gauges on it and pumped in some R134a until the pressures were correct. The situation only improved minimally.
Ideas?