Air Conditioning Problem
Thread Starter
3rd Gear
Joined: Aug 2006
Posts: 3
Likes: 0
From: California
Air Conditioning Problem
Newbie here… hello to all!
Since recently having my AC compressor rebuilt and the system recharged, I’ve noticed while driving, when I accelerate, the dash vents stop blowing all together and only the floor vents will blow. Then when I slow or come to a complete stop the dash vents will start to work again?
The dash vents always seemed to work fine before and have never had a problem… any ideas?
Sure is hot out here in this SoCal desert…
I would be very grateful if anyone could help me with this!
Thanks,
Mark
Since recently having my AC compressor rebuilt and the system recharged, I’ve noticed while driving, when I accelerate, the dash vents stop blowing all together and only the floor vents will blow. Then when I slow or come to a complete stop the dash vents will start to work again?
The dash vents always seemed to work fine before and have never had a problem… any ideas?
Sure is hot out here in this SoCal desert…
I would be very grateful if anyone could help me with this!
Thanks,
Mark
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
on the right side of the manifold, there is a three way t/checkvalve thingy.
make sure it's in good shape. They break. I am thinking you are having a vacuum related problem here... and that's a great place to start checking. The vacuum goes into the dash via the harness, so check it out.
good luck!
make sure it's in good shape. They break. I am thinking you are having a vacuum related problem here... and that's a great place to start checking. The vacuum goes into the dash via the harness, so check it out.
good luck!
Instructor
Joined: Jun 2006
Posts: 124
Likes: 0
From: Arlington Texas
Had same problem. My vaccuum hose was rotten between the 3-way (that Bogus spoke of ) and the front of the car somewhere. the hole was actually in the hose near the brake booster, but this line wraps around and attaches to something near front driverside wheelwell.
Thread Starter
3rd Gear
Joined: Aug 2006
Posts: 3
Likes: 0
From: California
Hey guys,
I had to order a vacuum pump with a gauge since mine didn’t have one.
Anyway, I’ve checked the entire system for leaks and haven’t found any?
Tested the round vacuum canister on the left front wheel well, the “T” from the manifold and all the lines from the “T”… no leaks???
I can’t find anything that looks like a vacuum line on the right side wheel well.
Is it possible that there’s an electric part of some sort, somewhere that switches the vacuum from upper vents to lower vents or to defroster vents?
I remember I used to be able to hear the vents open and close when I pressed the different buttons on the dash. It now seems that all for the air is blowing from the lower and defroster vents only, like the vents are stuck in Heater mode.
I had to order a vacuum pump with a gauge since mine didn’t have one.
Anyway, I’ve checked the entire system for leaks and haven’t found any?
Tested the round vacuum canister on the left front wheel well, the “T” from the manifold and all the lines from the “T”… no leaks???
I can’t find anything that looks like a vacuum line on the right side wheel well.
Is it possible that there’s an electric part of some sort, somewhere that switches the vacuum from upper vents to lower vents or to defroster vents?
I remember I used to be able to hear the vents open and close when I pressed the different buttons on the dash. It now seems that all for the air is blowing from the lower and defroster vents only, like the vents are stuck in Heater mode.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Vacuum runs from the source to the checkvalve with one side going through the firewall and the other to cruise and the tank in the left headlight well (where it's stored to provide a source during times of low vacuum). Once through the firewall, it either goes to the dash (manual air) or to the Programmer (electronic air), an electronic device that directs vacuum to any one of 4 solenoids that controls the position of the HVAC doors. Since the source appears to be good at least to the firewall (and your tank does hold vacuum?), you need to check it at the Programmer (assuming it's electronic air) - a postcard size device usually above the brake pedal or near the console above the accelerator. If it's good there, then a Bi-directional scanner comes in handy because it can emulate the Control Panel and send signals to the Programmer to see if it works. If it does, then you usually have a problem with the Dash Controls or if it doesn't, you need a new Programmer. Flat rate should be no more than an hour to check it out at a Dealer (should take all of 5 minutes).
Instructor
Joined: Jul 2005
Posts: 123
Likes: 0
Does anybody have a idea why my electronic air (-87) allways fade, when i drive longer trip? Blower blows at highest speed, but no air is coming out of vents. I assume that on of the doors closes gradually. But i have no idea, what it could be.
I really can hear blower motor blowing fast, but only very small amount of air is going out of vents. And it happens only, when i drive longer continuously.
I can fix it, if i put AC to ECON-position, and wait 1~2 minutes. Then it air flow from vents strenghts gradually. I wait until it blows powerfully, and then put it back to auto. Then i can drive half an hour without no problems, until air flow starts to fade again.
It is very annoying, car gets really hot inside when no air is coming in.
Also one of my friends is having same problem with his -87, so i think it can be common problem.
I really can hear blower motor blowing fast, but only very small amount of air is going out of vents. And it happens only, when i drive longer continuously.
I can fix it, if i put AC to ECON-position, and wait 1~2 minutes. Then it air flow from vents strenghts gradually. I wait until it blows powerfully, and then put it back to auto. Then i can drive half an hour without no problems, until air flow starts to fade again.
It is very annoying, car gets really hot inside when no air is coming in.
Also one of my friends is having same problem with his -87, so i think it can be common problem.
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Melting Slicks
Joined: Jul 2006
Posts: 3,356
Likes: 1
From: Chesapeake Va
Originally Posted by Mark_K
Hey guys,
I had to order a vacuum pump with a gauge since mine didn’t have one.
Anyway, I’ve checked the entire system for leaks and haven’t found any?
Tested the round vacuum canister on the left front wheel well, the “T” from the manifold and all the lines from the “T”… no leaks???
I can’t find anything that looks like a vacuum line on the right side wheel well.
Is it possible that there’s an electric part of some sort, somewhere that switches the vacuum from upper vents to lower vents or to defroster vents?
I remember I used to be able to hear the vents open and close when I pressed the different buttons on the dash. It now seems that all for the air is blowing from the lower and defroster vents only, like the vents are stuck in Heater mode.
I had to order a vacuum pump with a gauge since mine didn’t have one.
Anyway, I’ve checked the entire system for leaks and haven’t found any?
Tested the round vacuum canister on the left front wheel well, the “T” from the manifold and all the lines from the “T”… no leaks???
I can’t find anything that looks like a vacuum line on the right side wheel well.
Is it possible that there’s an electric part of some sort, somewhere that switches the vacuum from upper vents to lower vents or to defroster vents?
I remember I used to be able to hear the vents open and close when I pressed the different buttons on the dash. It now seems that all for the air is blowing from the lower and defroster vents only, like the vents are stuck in Heater mode.
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
Originally Posted by morgan_kane
Does anybody have a idea why my electronic air (-87) allways fade, when i drive longer trip? Blower blows at highest speed, but no air is coming out of vents. I assume that on of the doors closes gradually. But i have no idea, what it could be.
I really can hear blower motor blowing fast, but only very small amount of air is going out of vents. And it happens only, when i drive longer continuously.
I can fix it, if i put AC to ECON-position, and wait 1~2 minutes. Then it air flow from vents strenghts gradually. I wait until it blows powerfully, and then put it back to auto. Then i can drive half an hour without no problems, until air flow starts to fade again.
It is very annoying, car gets really hot inside when no air is coming in.
Also one of my friends is having same problem with his -87, so i think it can be common problem.
I really can hear blower motor blowing fast, but only very small amount of air is going out of vents. And it happens only, when i drive longer continuously.
I can fix it, if i put AC to ECON-position, and wait 1~2 minutes. Then it air flow from vents strenghts gradually. I wait until it blows powerfully, and then put it back to auto. Then i can drive half an hour without no problems, until air flow starts to fade again.
It is very annoying, car gets really hot inside when no air is coming in.
Also one of my friends is having same problem with his -87, so i think it can be common problem.
Team Owner
Joined: Oct 2000
Posts: 96,443
Likes: 9
From: Fort Knox, KY
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This is going to sound whack, but if you have the Electronic Climate Control System pull the ECM fuse for 30 seconds, then re-install.
This will clear all the stored codes and reset your system defaults.
I did this on my '92 and now my Electronic Climate Control HVAC system is working normally. Apparently the blender door function is controlled electronically in accordance with both interior temp sensor and panel temperature inputs.
If you've ruled out a vacuum leak and check valve, this is a logical next-step and cheap fix.
This will clear all the stored codes and reset your system defaults.
I did this on my '92 and now my Electronic Climate Control HVAC system is working normally. Apparently the blender door function is controlled electronically in accordance with both interior temp sensor and panel temperature inputs.
If you've ruled out a vacuum leak and check valve, this is a logical next-step and cheap fix.
Instructor
Joined: Jul 2005
Posts: 123
Likes: 0
Originally Posted by toptechx6
Your problem sounds more like the evaporator is freezing, the frost restricts the air flow, when you go to economy it defrosts. Clutch cycling switch or evaporator temperature switch is likely bad depending on which one your stsyem uses.
When using A/C in auto-position, does compressor stop in any situation? For example, if outside temp is colder than inside. I think my comp is allways running when using auto.
Can clutch cycling switch be changed without emptying refrigerant?
Last edited by morgan_kane; Sep 5, 2006 at 03:32 PM.
Instructor
Joined: Jul 2005
Posts: 123
Likes: 0
Originally Posted by onedef92
This is going to sound whack, but if you have the Electronic Climate Control System pull the ECM fuse for 30 seconds, then re-install.
This will clear all the stored codes and reset your system defaults.
I did this on my '92 and now my Electronic Climate Control HVAC system is working normally. Apparently the blender door function is controlled electronically in accordance with both interior temp sensor and panel temperature inputs.
If you've ruled out a vacuum leak and check valve, this is a logical next-step and cheap fix.
This will clear all the stored codes and reset your system defaults.
I did this on my '92 and now my Electronic Climate Control HVAC system is working normally. Apparently the blender door function is controlled electronically in accordance with both interior temp sensor and panel temperature inputs.
If you've ruled out a vacuum leak and check valve, this is a logical next-step and cheap fix.
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
Originally Posted by morgan_kane
VERY GOOD POINT, It did not even cross my mind.
When using A/C in auto-position, does compressor stop in any situation? For example, if outside temp is colder than inside. I think my comp is allways running when using auto.
Can clutch cycling switch be changed without emptying refrigerant?
When using A/C in auto-position, does compressor stop in any situation? For example, if outside temp is colder than inside. I think my comp is allways running when using auto.
Can clutch cycling switch be changed without emptying refrigerant?
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Power is cut to the compressor whenever the pressure drops low enough to make ice cubes (about 25 psi for R12; 22.5 psi for R134). It doesn't matter if it's on Auto - it matters what the pressure is when it hits the switch. Best to check it with a manifold gage set, but you can probably duplicate an icing situation by running it on max at about 1200 rpms and pulling the blower connector. The lack of air flow will drop the pressure and if you see ice on the evaporator outlet before the compressor cycles off, the low pressure switch is bad or needs to be adjusted.
You really should see what the pressure is to do either, partcularly if it's an R12 charge as the last low pressure switch I bought for my '89 (R12) was set at the R134 threshold or 22.5 psi. Didn't bother to check it until I noticed all the ice one day. Adjustable switches have a screw between the terminals. Turn it clockwise to reduce the cutoff threshold; clockwise to raise it.
As to changing the switch, it's on a schrader so you just unscrew - and screw it back - really fast, minimizing the loss of gas. Wear gloves, either refrigerant is about -32 at normal atmospheres.
You really should see what the pressure is to do either, partcularly if it's an R12 charge as the last low pressure switch I bought for my '89 (R12) was set at the R134 threshold or 22.5 psi. Didn't bother to check it until I noticed all the ice one day. Adjustable switches have a screw between the terminals. Turn it clockwise to reduce the cutoff threshold; clockwise to raise it.
As to changing the switch, it's on a schrader so you just unscrew - and screw it back - really fast, minimizing the loss of gas. Wear gloves, either refrigerant is about -32 at normal atmospheres.
Instructor
Joined: Jul 2005
Posts: 123
Likes: 0
Originally Posted by SunCr
Turn it clockwise to reduce the cutoff threshold; clockwise to raise it.
Is it counterclockwise to raise it?Thanks SunCr and Toptechx6 for the info.
I have r134a in the system, so maybe that's why i need to adjust. If switch is not adjustable, is there different switches in the market? What kind of switch should i buy? Or is adjustable best?
EDIT: I checked, and it has adjusting screw middle of it.
So, is this correct procedure to adjust:
I pull the blower connector, and let car idle with ac on. If/when i get icing on the evaporator outlet, i turn adjust screw to counterclockwise to raise cutoff pressure. Test again, and if no icing, good. ??
How much should i adjust screw at a time? Is one turn ok?
Last edited by morgan_kane; Sep 5, 2006 at 04:48 PM.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Counterclockwise to lower it - clockwise to raise it.
You really need a manifold gage set (about $80) and while observing the low side gage, pull the blower connector so you can see what the pressure is when it cuts off (and if it doesn't cutoff at all, you usually need a new switch). And if your Vette has been converted from R134, there's a possibility that somebody monkeyed with the switch and got it out of whack. On the other hand, if it's OEM and has never been touched, there's a stronger possibility that it needs to be replaced - most of these things can't go any lower than 20 psi. Anyway, assuming the compressor did cutoff, start by turning the screw 1/4 to 1/2 turn in the direction it needs to go and repeat the test while observing the gage. It takes a couple of trys (for me at least) to get it deadon, which for R134 would be 22.5 psi. If it's too low, you'll make ice; too high and the vent temps will rise - which since, you allready have that situation, is a good reason to see what your operating pressures are first - it might not be ice (even though it's suspect), and operating pressures (high and low) will narrow it down for you.
You really need a manifold gage set (about $80) and while observing the low side gage, pull the blower connector so you can see what the pressure is when it cuts off (and if it doesn't cutoff at all, you usually need a new switch). And if your Vette has been converted from R134, there's a possibility that somebody monkeyed with the switch and got it out of whack. On the other hand, if it's OEM and has never been touched, there's a stronger possibility that it needs to be replaced - most of these things can't go any lower than 20 psi. Anyway, assuming the compressor did cutoff, start by turning the screw 1/4 to 1/2 turn in the direction it needs to go and repeat the test while observing the gage. It takes a couple of trys (for me at least) to get it deadon, which for R134 would be 22.5 psi. If it's too low, you'll make ice; too high and the vent temps will rise - which since, you allready have that situation, is a good reason to see what your operating pressures are first - it might not be ice (even though it's suspect), and operating pressures (high and low) will narrow it down for you.
Team Owner
Joined: Oct 2000
Posts: 96,443
Likes: 9
From: Fort Knox, KY
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Originally Posted by morgan_kane
I have had battery cable disconnected often, but no effect. I also have checked vacuum leaks, and i believe doors work fine.