1996 LT4 AC charge
Thread Starter
Instructor
Joined: May 2002
Posts: 187
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From: Cumming Georgia
1996 LT4 AC charge
I recently purchased a 96 LT4. Now that the weather has warmed up, I realized that it was only blowing air, not cooling. I went to my local auto parts store and bought a recharge kit (with gauge) and followed the charging instructions. When I activate the charging trigger, the gauge cycles in and out of the green range (to the low side) as the compressor cycles. Is that normal? I am getting cooled AC now but wanted to know if that fluxuation represents another issue.
Melting Slicks
Joined: Jul 2008
Posts: 2,267
Likes: 142
From: Ottawa Ontario
Sounds like the A/C compressor is cycling on and off due to low refrigerant. You need to short out the low pressure switch to get the compressor to run until the gauge is at the correct reading. The switch is on the passenger side, on the upper A/C line just before the heater box IIRC.
Thread Starter
Instructor
Joined: May 2002
Posts: 187
Likes: 0
From: Cumming Georgia
That sound accurate as the system was most likely pretty empty when I started to recharge it. I have introduced two smalls cans of refrigerant into the system so far and it is definitely working better but still exhibiting this cycling behavior. Is there any downside to me just hooking up a third full can and charging more?
Drifting
Joined: Aug 2019
Posts: 1,334
Likes: 225
The compressor is supposed to cycle in order to prevent evap freezing, The cycling of on and off should be pretty equal in time, If the compressor cycles quickly, then it is undercharged, Another cheap way to make sure the system is charged properly is to feel both lines where they go into the passenger compt. When the lines feel pretty much the same (cold), then you're close.
Pro
Joined: Apr 2018
Posts: 557
Likes: 105
I just filled my 96 AC system after it had been sitting for many years. At first it would only cycle on a few seconds at a time. I would only pull the trigger on the can when the compressor was on and letting off when compressor would kick off. I did this and kept rocking the can side to side for quite some time. Eventually the compressor started staying on longer and longer. I was able to get 1.5 full big cans into the system. Now it blows very cold!!! That was several days ago and it it still working.
BUT with the car off I could hear just a tiny bit of noise on the Schrader valve on the low side. I mean I have to put my ear next to it to hear it. If I remove the valve to replace it will I need to pull a vacuum on it before I can fill it again?
BUT with the car off I could hear just a tiny bit of noise on the Schrader valve on the low side. I mean I have to put my ear next to it to hear it. If I remove the valve to replace it will I need to pull a vacuum on it before I can fill it again?
Drifting
Joined: Aug 2019
Posts: 1,334
Likes: 225
I just filled my 96 AC system after it had been sitting for many years. At first it would only cycle on a few seconds at a time. I would only pull the trigger on the can when the compressor was on and letting off when compressor would kick off. I did this and kept rocking the can side to side for quite some time. Eventually the compressor started staying on longer and longer. I was able to get 1.5 full big cans into the system. Now it blows very cold!!! That was several days ago and it it still working.
BUT with the car off I could hear just a tiny bit of noise on the Schrader valve on the low side . I mean I have to put my ear next to it to hear it. If I remove the valve to replace it will I need to pull a vacuum on it before I can fill it again?
BUT with the car off I could hear just a tiny bit of noise on the Schrader valve on the low side . I mean I have to put my ear next to it to hear it. If I remove the valve to replace it will I need to pull a vacuum on it before I can fill it again?
Last edited by Mrvettenick; Apr 8, 2021 at 03:25 PM.
Melting Slicks
Joined: Jul 2008
Posts: 2,267
Likes: 142
From: Ottawa Ontario
There are actually tools available that allow you to replace the schrader valve without losing all the refrigerant.
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Instructor
Joined: May 2020
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From: Northeast, Ohio
There are actually tools available that allow you to replace the schrader valve without losing all the refrigerant.
https://www.amazon.ca/dp/B0015KH93K/...ing=UTF8&psc=1
https://www.amazon.ca/dp/B0015KH93K/...ing=UTF8&psc=1
