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Discussion Starter #1
What is the most accurate/important reading on the gauge?

I get a reading of 25 with the car on and A/C on high and the same with the car off. With the car on and A/C off I am getting a reading of about 45. I am assuming that the 25 with the car on and A/C on high is not the one because when I added one can it was 25 and after adding the second can it stayed at 25. Please advise.
 

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Usually when reading guages you want the AC on max. 25 seems a little low to me so something doesn't sound right. Hard to really say without seeing th ehigh side of the system. What air temp do you have at the center vent with the AC on max and the car shut up tight? I would be careful adding much more.
 

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It's good to have a gauge on the high pressure side also. Plus a good
thermometer in the supply air grille. On late model A/Cs, they only hold
a total of 2 cans (16oz each). My Z holds 1.75 pounds of 134 for instance.
Usually rev the engine a little (2k) and add refrigerant until it stops kicking
on and off and your pretty close.
Good luck
 

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Discussion Starter #4
This is what is so confusing. I put one can in and with the car on and A/c on high it read 25. A/c was working fine, just on a real hot day it could have been a little better. So I add another can and with the car and A/c on high.. and same thing with the engine on and A/C on high still 25. But after the second can with the engine on and A/C off I am getting a reading of about 45...very confused. I kind of figured that from all I read the way to read is with the engine and A/C on. The A/c is pretty cold and I have 2 13oz cans in. I did not take the air temp yet though.
 

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I'd have to check my service manual to be 100% sure, but my understanding is add R-134a when the engine and A/C is on. I noticed the pressure also dips a little when you step on the gas, so I slowly added R-134a until the A/C felt good at 1.5k-2.0k rpm (cruising range). I did this over a course of several days to make sure I did not overfill. Also, I never looked at the pressure with the A/C off.

If you bought one of those cheap kits with a low pressure gauge, its probably not very accurate. I don't think mine is because I tried following the service manual pressure for the low side and the A/C was still only cool, not cold. My gauge also did not give correct pressure when releasing the refrigerant, so it was a add a little, stop, check, and add a little process. My end pressure ended up in the mid to low 30's at idle according to my el cheapo gauge.
 

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If you now have cold air I would leave alone. If you have to add more than two 13oz cans you probably have a major leak in the system as you have added 1.625Lbs to a 1.77Lbs.system. I would also not trust the guage that you are using. I would be confused by those readings as well.
 

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True-DO NOT OVERFILL

It's good to have a gauge on the high pressure side also. Plus a good
thermometer in the supply air grille. On late model A/Cs, they only hold
a total of 2 cans (16oz each). My Z holds 1.75 pounds of 134 for instance.
Usually rev the engine a little (2k) and add refrigerant until it stops kicking
on and off and your pretty close.
Good luck
True it is best not overfill the system, it will not cool properly. As you pointed out putting a household thermometer in front of center vent is a good idea, should cool to just below 50F at vent. Run engine with A/C on max cool,add 134 with can upright,shake can a little but don't invert as it will liquid fill the system too fast and could harm compressor.Feel the low pressure line just before it goes into the firewall,should feel like a cold beer just out of the cooler. We know a lot about A/C here in Florida with our hot summers but it is a good idea to have a professional check up if you are not sure how to proceed.:agree: :buhbye:
V8GRA
 
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