AC Compressor won't stay on

Oakway9092

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Hey y'all.

I've been trying to dig around here to see if someone has a similar issue to my AC and I seem to reach the dead end of my knowledge.

I have a 1997 V6 in which I replaced the Compressor, Condenser, Accumulator, Evaporator, Charge Ports and both the High and Low Pressure Switches. I vacuumed the system as well and checked for leaks. Everything good so far...

Now here's where I'm wondering what went wrong/what is going wrong:

When I add the first can, the AC compressor kicks on and off (Cooling fan stays on)
When I add the second can, the on and off is alot less frequent
When I add about 1/4th of the third can, the compressor shuts off completely (but the cooling fan stays on)

I mess with the AC switch inside the car (going from VENT to NORM A/C) and the compressor kicks on for about three seconds with a heavy draw but shuts off and the cooling fan stays on all the time. Moving the switch repeatedly, I noticed that it gets pretty cold inside and there's condensation along the hoses. I noticed on my AC gauge that it goes from the Red area to Yellow to Green each time the compressor is on but once its off it steadily runs back to the red.

I checked all fuses...good. The connectors to the Switches and Coil...good. With the car on Key On Engine Off, I can hear the CCRM click and the AC Clutch kick on.

And I bypassed the Low Pressure Switch and I still get the same result!

Has anyone had an issue as this? I seriously have no clue on what to do. Any help would be appreciated!
 

RAU03MACH

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Make sure no leaks are found
And add the right amount of freion
And also use a Guage set to see what is going on
Sounds low to me
But I am not there to see the proble
Also the ac clutch dose not stay on consistently it dose need to cycle at some point
 

cobrajeff96

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Might be the high pressure switch is seeing too high a pressure. It engages the A/C clutch which then pressurizes the whole system pretty high, the switch sees it, and then promptly shuts it down. Might have overfilled it. Should be a sticker under the hood toward the front of it that tells exactly how much kg of refrigerant to put into the system.

Or it could just be that the switch itself is faulty.
 

07GtS197

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The biggest question, what are the discharge temps? If it’s getting to where it should be you’re fine. The compressor isn’t supposed to be on continuously. An efficient system will run for short periods of time because they don’t need the compressor to keep the evaporator cool.

I would get a set of manifold gauges to check head pressure while you’re at it. Using those gauges that come with the cam doesn’t tell you much. The low side can tell you a lot but the high side will give you the whole picture.
 

lwarrior1016

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These cars have a built in orifice in the liquid line right? If that wasn’t replaced, it might be clogged creating high high side pressure and shutting it down.
 
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Oakway9092

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Hey guys!

Thanks for the replies! I managed to pick up a gauge set and here were the readings:

With the AC off:
Low 87psi
High 95psi

With the AC on:
Low 18psi
High 155psi

The compressor kicked on 4 times and then stopped.
 

07GtS197

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Those readings are really low. What are the ambient temps like? Either way it looks like you need to add more refrigerant. Here’s a chart I use

D0DD0088-89E0-4B65-8115-911912CA0CF9.jpeg
 

TTSaleen

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As you indicated, your low side pressure is under the required minimum for R134a.
As suggested, you need to ensure you put the proper amount of freon in the car (34 ounces) and don't overfill it.
Your high side pressure will increase on its own as you fill the low side and based on your external temperatures, you should follow the chart above to see where it should be.
It's not that hard but having the proper gauges is a must!

I recently did a video on this for my own SN95.
I'll post it here if you might find it helps.

I found my low side pressure switch was intermittent so I had to bypass it with a jumper wire to ensure I filled the system properly.
After a few weeks, the switch eventually failed and I had to swap it out.
I also later on had to swap the entire compressor as the clutch failed and would not stay engaged.
Happy to report that as of today, it works great but it took me a little trial-and-error to get it fixed.
Good luck!

 
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Oakway9092

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As you indicated, your low side pressure is under the required minimum for R134a.
As suggested, you need to ensure you put the proper amount of freon in the car (34 ounces) and don't overfill it.
Your high side pressure will increase on its own as you fill the low side and based on your external temperatures, you should follow the chart above to see where it should be.
It's not that hard but having the proper gauges is a must!

I recently did a video on this for my own SN95.
I'll post it here if you might find it helps.

I found my low side pressure switch was intermittent so I had to bypass it with a jumper wire to ensure I filled the system properly.
After a few weeks, the switch eventually failed and I had to swap it out.
I also later on had to swap the entire compressor as the clutch failed and would not stay engaged.
Happy to report that as of today, it works great but it took me a little trial-and-error to get it fixed.
Good luck!

Thanks for the vid! Oh and is it normal for the low side pressure to rise up to 90 once the compressor is off?
 

07GtS197

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Once the compressor turns off the low side rises and high side lowers. This is static pressure and should be equal on both sides.
 

lwarrior1016

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No. The high side is normally closed and sends power to the low side. High side goes open in the case on an over pressure situation.
 

TTSaleen

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Thanks for the vid! Oh and is it normal for the low side pressure to rise up to 90 once the compressor is off?
No problem. Yes when the compressor is off, the low side will rise and that is perfectly normal.

As I mentioned, here's my updated video of the switch I had to replace.

 
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Oakway9092

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Hey y'all!

A little update:

I jumped the low side and it kicked on for a few times and got cold but the compressor cut off.

I've been thinking...should I give it a vacuum again?
 
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Oakway9092

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What was the high side doing when you jumped the compressor?
Sorry I couldn't reply, work got in the way!

Well a little update.

I gave it a vacuum again and now my readings are different:

Low Side: 77 psi
Hi Side: 0 psi (even below that!)

As the car warmed up, the Lo Side went up to 82psi.
 

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