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Discussion Starter · #1 ·
Auto a/c …. I’ve countlessly searched through the forum trying to figure out why my clutch isn’t engaging. Old A/C compressor was changed because of a bad clutch but it still blew cold air when it would work. I changed it along with the drier and had the system vacuumed and refilled at a shop, no leaks. I Bypass the relay and it clicks, blows ice cold. No red dot on screen still shows frost symbol. I know there have been many people who’ve had a similar problem with this so I’m hoping anyone whose experienced this can help me get on the right track to figure out was causing it to not engage.
 

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1992 3000GT VR4
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Make sure your AC pressure sensor (Switch) is good
It is on the Drier
If it doesn't see pressure it won't turn the AC compressor clutch on (check your relay as well)
If everything was working as it was supposed to before the swapping of parts... my guess is that you have a bad pressure switch
You can check to see if your new AC compressor clutch works correctly by unplugging it
Using a Power Probe testing lead to see if your getting power and ground from harness side
Then test the compressor with it make sure it's not a faulty compressor clutch by carefully powering it on with probe (unplugged from harness to keep the power your sending to it isolated to the AC clutch)
Now if your not seeing power + or a Ground - signal or either or pin in the ac clutch harness pigtail
Your gonna have to diag it a little further...
But at least 1 reference ground or power is good.. meaning it's not getting a closed circuit to power on the ac clutch
If you never used a power probe I would seek out a mechanic that knows how to or has one on hand to help you
You can surely make things more difficult with this tool if not done correctly ( shorting things out burning things up real quick )
But the pressure switch for AC system is what cycles power to the compressor clutch sending signal to turn it off and on thru the Ac relay
With the build up of pressure its seeing
If the pressure switch is bad the clutch will not get engage
Double check your Radiator fans as well .... when AC is turned on
both should be working regardless if the car is warmed up or not
Hope this helps 👍
 

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Registered
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23 Posts
Discussion Starter · #3 ·
Make sure your AC pressure sensor (Switch) is good
It is on the Drier
If it doesn't see pressure it won't turn the AC compressor clutch on (check your relay as well)
If everything was working as it was supposed to before the swapping of parts... my guess is that you have a bad pressure switch
You can check to see if your new AC compressor clutch works correctly by unplugging it
Using a Power Probe testing lead to see if your getting power and ground from harness side
Then test the compressor with it make sure it's not a faulty compressor clutch by carefully powering it on with probe (unplugged from harness to keep the power your sending to it isolated to the AC clutch)
Now if your not seeing power + or a Ground - signal or either or pin in the ac clutch harness pigtail
Your gonna have to diag it a little further...
But at least 1 reference ground or power is good.. meaning it's not getting a closed circuit to power on the ac clutch
If you never used a power probe I would seek out a mechanic that knows how to or has one on hand to help you
You can surely make things more difficult with this tool if not done correctly ( shorting things out burning things up real quick )
But the pressure switch for AC system is what cycles power to the compressor clutch sending signal to turn it off and on thru the Ac relay
With the build up of pressure its seeing
If the pressure switch is bad the clutch will not get engage
Double check your Radiator fans as well .... when AC is turned on
both should be working regardless if the car is warmed up or not
Hope this helps 👍
Dude seriously thank u for taking the time to type this I really appreciate it. It’s heating quickly by the week so this’ll definitely help.
 

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1992 3000GT VR4
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1,178 Posts
Dude seriously thank u for taking the time to type this I really appreciate it. It’s heating quickly by the week so this’ll definitely help.
Not a problem but I would definitely check things out and go completely thru it again just double checking things ....
But I'm pretty sure it's your pressure sensor ( switch)
Might have to evac it and recharge it again .... not 100% sure if there is a Schrader valve under it or not .... I don't think ther is ( pressure switch on the drier if you remove it you might get R134A gassed!! )
 
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