Can't get cold air in ???
Former Vendor
Joined: Apr 2009
Posts: 766
Likes: 3
From: Charlotte North Carolina 704-394-5150
I guess this is for your 81? It does make a difference so we know what style of a/c system you have.
First off you have to make sure that you have vacuum getting to your a/c heater control unit. Over by your power brake booster there will be a series of vacuum lines that connect to a "t" vacuum fitting. Two of the lines will be about 1/4" and one will be smaller about 1/8". This small hose runs over to your passenger side of the firewall area, 9behind your valve cover area) and goes into theh large rubber grommet where you see twoother vacuum hoses of the same size coming out of. One of these hoses at the grommet will go to your hot water shut off valve, and the other goes to the vacumm pod that is mounted under the upper portion of your fender near the windshield, it is accessed through the wiper/cowl area.
Carefully remove your side console strip on the passenger side. You can see teh vacuum connector that is attached to your a/c heater control unit. This vacuum switch ( which often times goes bad) can be eaasily removed and installed. But you can first try cranking the car and slide te top lever back and forth and listen for air "hissing". If you hear air hissing, thehn you have a vacuum supply to this switch, which is important. BUt if the vacuum hissiing is loud and will not stop when you are moving the lever, then you may need to replace this vacuum switch. they are cheap.
If you have no vacuum hissing, then you have a problem in the mhose from that "t:" fitting to the control unit. Which also often occurs.
Ok lets say you got everything corrected.
The heater hose coming off of the front of the intake manifold on the passenger side runs back to your heater core. In this hose ther should be a shut off valve that is vacuum controlled. DO you have this valve?
If you have this valve. Remove the vacuum hose connected to it. Crank the engine and have someone move your hot/cold lever back and forth. When they are doing this, see if you get vacuum to this hose or not. If you get vacuum great, if you dont. You will need to remove your glove box liner and possible replace the vacuum switch that is bolted to the TOP of your heater box where the cable for hot/cold connects to a lever that activates this vacuum switch.
One IMPORTANT thing to remember. That when you are going to A/C. the hot water valve should shut so not to allow hot water to conflict with the a/c function. So you may need to remove the hot water valve and check it. These hot water valves can look teh SAME but be TOTALLY different.
IF when you want A/C. The vacuum line going to the shut off valve let say has VACUUM. Then you want to MAKE TOTALLY SURE that when vacuum is applied to this valve it will close and let no water pass. These valves come TWO way, normally OPEN or CLOSED. so making sure that you have the correct type is important depending on the way that the vacuum is or is not going to the shut off valve at the time that you ****ch the hot/cold lever to COLD.
"DUB"
First off you have to make sure that you have vacuum getting to your a/c heater control unit. Over by your power brake booster there will be a series of vacuum lines that connect to a "t" vacuum fitting. Two of the lines will be about 1/4" and one will be smaller about 1/8". This small hose runs over to your passenger side of the firewall area, 9behind your valve cover area) and goes into theh large rubber grommet where you see twoother vacuum hoses of the same size coming out of. One of these hoses at the grommet will go to your hot water shut off valve, and the other goes to the vacumm pod that is mounted under the upper portion of your fender near the windshield, it is accessed through the wiper/cowl area.
Carefully remove your side console strip on the passenger side. You can see teh vacuum connector that is attached to your a/c heater control unit. This vacuum switch ( which often times goes bad) can be eaasily removed and installed. But you can first try cranking the car and slide te top lever back and forth and listen for air "hissing". If you hear air hissing, thehn you have a vacuum supply to this switch, which is important. BUt if the vacuum hissiing is loud and will not stop when you are moving the lever, then you may need to replace this vacuum switch. they are cheap.
If you have no vacuum hissing, then you have a problem in the mhose from that "t:" fitting to the control unit. Which also often occurs.
Ok lets say you got everything corrected.
The heater hose coming off of the front of the intake manifold on the passenger side runs back to your heater core. In this hose ther should be a shut off valve that is vacuum controlled. DO you have this valve?
If you have this valve. Remove the vacuum hose connected to it. Crank the engine and have someone move your hot/cold lever back and forth. When they are doing this, see if you get vacuum to this hose or not. If you get vacuum great, if you dont. You will need to remove your glove box liner and possible replace the vacuum switch that is bolted to the TOP of your heater box where the cable for hot/cold connects to a lever that activates this vacuum switch.
One IMPORTANT thing to remember. That when you are going to A/C. the hot water valve should shut so not to allow hot water to conflict with the a/c function. So you may need to remove the hot water valve and check it. These hot water valves can look teh SAME but be TOTALLY different.
IF when you want A/C. The vacuum line going to the shut off valve let say has VACUUM. Then you want to MAKE TOTALLY SURE that when vacuum is applied to this valve it will close and let no water pass. These valves come TWO way, normally OPEN or CLOSED. so making sure that you have the correct type is important depending on the way that the vacuum is or is not going to the shut off valve at the time that you ****ch the hot/cold lever to COLD.
"DUB"
Thread Starter
Intermediate
Joined: Aug 2008
Posts: 32
Likes: 0
From: Tronto ON
I guess this is for your 81? It does make a difference so we know what style of a/c system you have.
First off you have to make sure that you have vacuum getting to your a/c heater control unit. Over by your power brake booster there will be a series of vacuum lines that connect to a "t" vacuum fitting. Two of the lines will be about 1/4" and one will be smaller about 1/8". This small hose runs over to your passenger side of the firewall area, 9behind your valve cover area) and goes into theh large rubber grommet where you see twoother vacuum hoses of the same size coming out of. One of these hoses at the grommet will go to your hot water shut off valve, and the other goes to the vacumm pod that is mounted under the upper portion of your fender near the windshield, it is accessed through the wiper/cowl area.
Carefully remove your side console strip on the passenger side. You can see teh vacuum connector that is attached to your a/c heater control unit. This vacuum switch ( which often times goes bad) can be eaasily removed and installed. But you can first try cranking the car and slide te top lever back and forth and listen for air "hissing". If you hear air hissing, thehn you have a vacuum supply to this switch, which is important. BUt if the vacuum hissiing is loud and will not stop when you are moving the lever, then you may need to replace this vacuum switch. they are cheap.
If you have no vacuum hissing, then you have a problem in the mhose from that "t:" fitting to the control unit. Which also often occurs.
Ok lets say you got everything corrected.
The heater hose coming off of the front of the intake manifold on the passenger side runs back to your heater core. In this hose ther should be a shut off valve that is vacuum controlled. DO you have this valve?
If you have this valve. Remove the vacuum hose connected to it. Crank the engine and have someone move your hot/cold lever back and forth. When they are doing this, see if you get vacuum to this hose or not. If you get vacuum great, if you dont. You will need to remove your glove box liner and possible replace the vacuum switch that is bolted to the TOP of your heater box where the cable for hot/cold connects to a lever that activates this vacuum switch.
One IMPORTANT thing to remember. That when you are going to A/C. the hot water valve should shut so not to allow hot water to conflict with the a/c function. So you may need to remove the hot water valve and check it. These hot water valves can look teh SAME but be TOTALLY different.
IF when you want A/C. The vacuum line going to the shut off valve let say has VACUUM. Then you want to MAKE TOTALLY SURE that when vacuum is applied to this valve it will close and let no water pass. These valves come TWO way, normally OPEN or CLOSED. so making sure that you have the correct type is important depending on the way that the vacuum is or is not going to the shut off valve at the time that you ****ch the hot/cold lever to COLD.
"DUB"
First off you have to make sure that you have vacuum getting to your a/c heater control unit. Over by your power brake booster there will be a series of vacuum lines that connect to a "t" vacuum fitting. Two of the lines will be about 1/4" and one will be smaller about 1/8". This small hose runs over to your passenger side of the firewall area, 9behind your valve cover area) and goes into theh large rubber grommet where you see twoother vacuum hoses of the same size coming out of. One of these hoses at the grommet will go to your hot water shut off valve, and the other goes to the vacumm pod that is mounted under the upper portion of your fender near the windshield, it is accessed through the wiper/cowl area.
Carefully remove your side console strip on the passenger side. You can see teh vacuum connector that is attached to your a/c heater control unit. This vacuum switch ( which often times goes bad) can be eaasily removed and installed. But you can first try cranking the car and slide te top lever back and forth and listen for air "hissing". If you hear air hissing, thehn you have a vacuum supply to this switch, which is important. BUt if the vacuum hissiing is loud and will not stop when you are moving the lever, then you may need to replace this vacuum switch. they are cheap.
If you have no vacuum hissing, then you have a problem in the mhose from that "t:" fitting to the control unit. Which also often occurs.
Ok lets say you got everything corrected.
The heater hose coming off of the front of the intake manifold on the passenger side runs back to your heater core. In this hose ther should be a shut off valve that is vacuum controlled. DO you have this valve?
If you have this valve. Remove the vacuum hose connected to it. Crank the engine and have someone move your hot/cold lever back and forth. When they are doing this, see if you get vacuum to this hose or not. If you get vacuum great, if you dont. You will need to remove your glove box liner and possible replace the vacuum switch that is bolted to the TOP of your heater box where the cable for hot/cold connects to a lever that activates this vacuum switch.
One IMPORTANT thing to remember. That when you are going to A/C. the hot water valve should shut so not to allow hot water to conflict with the a/c function. So you may need to remove the hot water valve and check it. These hot water valves can look teh SAME but be TOTALLY different.
IF when you want A/C. The vacuum line going to the shut off valve let say has VACUUM. Then you want to MAKE TOTALLY SURE that when vacuum is applied to this valve it will close and let no water pass. These valves come TWO way, normally OPEN or CLOSED. so making sure that you have the correct type is important depending on the way that the vacuum is or is not going to the shut off valve at the time that you ****ch the hot/cold lever to COLD.
"DUB"
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Former Vendor
Joined: Apr 2009
Posts: 766
Likes: 3
From: Charlotte North Carolina 704-394-5150
The aftermarket intake manifold is not the issue. If you have a vacuum fitting in the intake manifold behind the carb, it is the supply for your headlights and your heater-a/c control unit.
Did you check any of what I wrote to you to check and get back on?
Is your car an 81?
I want to help but without you checking some of these issuesand responding with what you have found, it is an aweful long drive to my shop.
Many on teh forum call me at work (704)394-5150 and you are welcome to do the same. But try to be able to be with the car so I can direct you in certian things to check. It was laid out in my first response.
"DUB"
Did you check any of what I wrote to you to check and get back on?
Is your car an 81?
I want to help but without you checking some of these issuesand responding with what you have found, it is an aweful long drive to my shop.
Many on teh forum call me at work (704)394-5150 and you are welcome to do the same. But try to be able to be with the car so I can direct you in certian things to check. It was laid out in my first response.
"DUB"
Former Vendor
Joined: Apr 2009
Posts: 766
Likes: 3
From: Charlotte North Carolina 704-394-5150
LOOK and see if you have a valve that is in-line in the hose that goes from the top of your intake towards your heater core. If you do, then the instructions will work partly. Your design of dash does not have a glovebox, so you would need to remove the right side dash panel, and teh a/c-heater controls are really a PAIN to access. Unlike the 1977-1982 controls. But it all depends... I really would like for you to call me.
IF you have time ...PLEASE CALL ME at my shop. When you can be at your car and answer some questions so I can direct you in correcting this problem.
"DUB"
(704) 394-5150 EST
IF you get the answering machine ...LEAVE your number and I will call you back.
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Thread Starter
Intermediate
Joined: Aug 2008
Posts: 32
Likes: 0
From: Tronto ON
hot air out the vent's
Sorry for not getting back to you sooner ,i have been working allot and havent had the time to check .
i am going to do it first thing in the morning .
The car is a 1981 corvette .
And thank you again for all the input in helping me with this problem .
I will call you if the problem persists.
i am going to do it first thing in the morning .
The car is a 1981 corvette .
And thank you again for all the input in helping me with this problem .
I will call you if the problem persists.
