'95 Z28 with A/C issue... hissing when off and when on MAX and etc.
10-28-2009, 10:05 PM
#1
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Location: Dallas, Texas
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'95 Z28 with A/C issue... hissing when off and when on MAX and etc.
Let me start this off with the fact that I know when you normally turn off the A/C in a 4th gen, it makes a decompression sound.
What's new is that the car now makes it full time when the car is running. When the car is in accessory mode, there's no hiss when changing between different modes--it's normal. This implied to me that the compressor went out, but it still blows freezing cold air.
This is very annoying, as when turned in the OFF position, it hisses loudly the entire time you drive. In Max, it does the same, but slightly quieter. A/C it barely hisses. Blue foot and face it doesn't hiss at all. White face, it barely hisses. White feet, it hisses more than the other heat modes. White feet and defrost, it hisses. Defrost, it does not hiss at all.
I took a video, but it'll be hard to detect with your ears unless you turn it up pretty loud. The hissing comes through the camera as being a cricket chirping sound.
As I said, the A/C is blowing freezing cold still despite this hiss, and when turned to OFF it does not blow air, just loudly hisses. Around 100 days ago, my sister had to have the A/C control switch (which was the dealership's vague name (which annoyed the hell out of me when I was looking at my parts manual) for quite literally the thing in the dash with 3 ***** on it AKA HVAC Switches) replaced because the mechanic determined that it was the reason the A/C wouldn't cool. What is written on the receipt was...
"299 REPLACED SWITCH
15298 CP, $268.24
16147649 SWITCH, A/, $37.84
86943 INTERNAL FAILURE IN SWITCH 299 INTERNAL OPEN IN A/C CONTROL SWITCH NOT GIVING GROUND SIGNAL TO A/C RELAY. REPLACE SWITCH"
That solved the problem where the A/C wouldn't get cold.
Now my sister has the new problem.
Ideas?
What's new is that the car now makes it full time when the car is running. When the car is in accessory mode, there's no hiss when changing between different modes--it's normal. This implied to me that the compressor went out, but it still blows freezing cold air.
This is very annoying, as when turned in the OFF position, it hisses loudly the entire time you drive. In Max, it does the same, but slightly quieter. A/C it barely hisses. Blue foot and face it doesn't hiss at all. White face, it barely hisses. White feet, it hisses more than the other heat modes. White feet and defrost, it hisses. Defrost, it does not hiss at all.
I took a video, but it'll be hard to detect with your ears unless you turn it up pretty loud. The hissing comes through the camera as being a cricket chirping sound.
As I said, the A/C is blowing freezing cold still despite this hiss, and when turned to OFF it does not blow air, just loudly hisses. Around 100 days ago, my sister had to have the A/C control switch (which was the dealership's vague name (which annoyed the hell out of me when I was looking at my parts manual) for quite literally the thing in the dash with 3 ***** on it AKA HVAC Switches) replaced because the mechanic determined that it was the reason the A/C wouldn't cool. What is written on the receipt was...
"299 REPLACED SWITCH
15298 CP, $268.24
16147649 SWITCH, A/, $37.84
86943 INTERNAL FAILURE IN SWITCH 299 INTERNAL OPEN IN A/C CONTROL SWITCH NOT GIVING GROUND SIGNAL TO A/C RELAY. REPLACE SWITCH"
That solved the problem where the A/C wouldn't get cold.
Now my sister has the new problem.
Ideas?
10-29-2009, 05:09 AM
#2
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Join Date: Sep 2004
Posts: 0
Sounds as though either one of the vac lines is off at the switch assy or at one of the actuators.
Does anyone happen to notice that when the AC is set to the front vents and you put your foot into the accelerator, it switches to floor and defrost for a few moments and then comes back to the front vents?
Does anyone happen to notice that when the AC is set to the front vents and you put your foot into the accelerator, it switches to floor and defrost for a few moments and then comes back to the front vents?
10-29-2009, 07:05 AM
#3
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Join Date: Dec 1969
Location: Little Rock, AR
Posts: 27,709
Trace the sound of the hiss. You have a vacuum control line leaking under the dash.
Speedy, was that question open to all or directed to the OP? When you stomp on the gas, engine vacuum goes low. If there is not enough vacuum stored in the canister (or there is a small leak in the system) the HVAC controls will not get enough vacuum to keep the vent door open. Default position is floor and defrost when there is no vacuum.
Speedy, was that question open to all or directed to the OP? When you stomp on the gas, engine vacuum goes low. If there is not enough vacuum stored in the canister (or there is a small leak in the system) the HVAC controls will not get enough vacuum to keep the vent door open. Default position is floor and defrost when there is no vacuum.
10-29-2009, 11:19 AM
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10-29-2009, 04:50 PM
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It was for the person that started the thread. I don't know what an op is. The reason I stated it the way I did was I meant either him or his SO. I do know what the cause of the problem is with regard to my question. Since I had it happen to me.
But my question still stands. Do you notice if the vents changed as described?
For Brangeta, I suggest you start by removing the controller and pull and test each hose individually for the ability to hold vacuum. Then we move outside the dash if that doesn't show anything.
The solution will depend on the problem.
But my question still stands. Do you notice if the vents changed as described?
For Brangeta, I suggest you start by removing the controller and pull and test each hose individually for the ability to hold vacuum. Then we move outside the dash if that doesn't show anything.
The solution will depend on the problem.
11-02-2009, 11:19 PM
#9
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Location: Dallas, Texas
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Sorry, Halloween and the days before it took up a lot of my CZ28 time.
Sister took it to the Pontiac dealership (it's closer than Chevy) and had them look at it. They said the vac line behind the A/C controls is needing replacement, but the part has been discontinued. They told me to go to a junkyard and get one and put it on.
Part #16159553
I haven't had time to look for the part because of work and Halloween. Haven't been in the car since the video I made either.
I don't know anything about the vents changing when getting on the gas. It's my sister's daily driver and I rarely drive it.
Going to have to delve into this sometime next week... Not looking forward to it, since this isn't an area of the car I know anything about...
Sister took it to the Pontiac dealership (it's closer than Chevy) and had them look at it. They said the vac line behind the A/C controls is needing replacement, but the part has been discontinued. They told me to go to a junkyard and get one and put it on.
Part #16159553
I haven't had time to look for the part because of work and Halloween. Haven't been in the car since the video I made either.
I don't know anything about the vents changing when getting on the gas. It's my sister's daily driver and I rarely drive it.
Going to have to delve into this sometime next week... Not looking forward to it, since this isn't an area of the car I know anything about...
11-03-2009, 04:52 PM
#10
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No one really knows it. We just go with what the problem shows. I still suggest you pull the hoses off the controller. I think they are all color coded. Put a device that pulls vacuum in each hose to see if it holds vacuum like a mity-vac brake bleeder. If you really can't come up with anything, use a tube and your mouth.
When you find the one that doesn't hold vacuum, let us know. You may also want to pay attention to any vents that don't work when you change the controls.
When you find the one that doesn't hold vacuum, let us know. You may also want to pay attention to any vents that don't work when you change the controls.
Last edited by Guest47904; 11-03-2009 at 04:54 PM.
11-03-2009, 07:01 PM
#11
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If I have the time this weekend to do it, I'll just have to visually inspect it, and if that doesn't lead to some conclusions, I'll locate the parts somewhere and buy the entire thing and sell the extra stuff or whatever I guess.
Any hints on how to get into that area? I've never done it and certainly don't want to damage the car.
The car may be old, but it's about as mint as mint can be, so breaking plastic tabs and such by pulling on crap is simply out of the question.
Any hints on how to get into that area? I've never done it and certainly don't want to damage the car.
The car may be old, but it's about as mint as mint can be, so breaking plastic tabs and such by pulling on crap is simply out of the question.
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