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Discussion Starter #1
So... if I was to put some foam insulation around the a/c lines under the hood, would that yield a noticeable difference in the temperature at my air vents when the a/c is working hard? I was driving home today with the a/c on max cooling the car after it had been baking in sun for a few hours and it took about 20 minutes before the fan started to slow down. Anyone done this? Would it be worth it?
 

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So... if I was to put some foam insulation around the a/c lines under the hood, would that yield a noticeable difference in the temperature at my air vents when the a/c is working hard? I was driving home today with the a/c on max cooling the car after it had been baking in sun for a few hours and it took about 20 minutes before the fan started to slow down. Anyone done this? Would it be worth it?
Short answer - no. Won't make any difference.

Mitch
 

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WOT Junkie and avid corn burner
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+1. Have you checked your refrigerant charge lately? Low side pressure should be 25-45psi, and the high side should be 125-230psi. At idle with the A/C on Max A/C, blower on high, the low side pressure should not be varying (compressor engaging and disengaging). I set my pressures at about 33psi for the low side and about 200psi for the high side. My A/C starts blowing cold within 30 seconds of the A/C being turned on. This is also when the car sits in 80-90*+ heat all day.
 

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Discussion Starter #4
I personally don't know the charge on the system... but I should be able to have it checked in a jiffy. It blows cold, it's just I think it could be a bit cold-er. I know the system can take up to 2 lb 2 oz of charge and I think they put in 2 lb, so... hard to say. Would 2 oz. make that big a difference?
 

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No, not really. But how long ago was your system recharged? I usually have to check my charge every year. About every year and a half, I have to top off my system. This is actually quite typical of most MN12 A/C systems. At least it was like that on my dad's two Super Coupes and his '95 LX that he has had in the past. Then again we use our A/C all the time in our cars. Before I recently recharged my system, it would take a good 20 minutes or so untill the A/C was somewhat cold. Those pressures are what matters the most though. If your system has not been refilled in a year or so, you most likely need some refrigerant.
 

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No, not really. But how long ago was your system recharged? I usually have to check my charge every year. About every year and a half, I have to top off my system. This is actually quite typical of most MN12 A/C systems. At least it was like that on my dad's two Super Coupes and his '95 LX that he has had in the past. Then again we use our A/C all the time in our cars. Before I recently recharged my system, it would take a good 20 minutes or so untill the A/C was somewhat cold. Those pressures are what matters the most though. If your system has not been refilled in a year or so, you most likely need some refrigerant.
It's not typical. Had the same charge in my 3.8L system for 7 years. Blew cold instantly and stayed like that as long as it was on. Didn't matter how hot it would get outside, it would still have discharge temps out of the center outlet at around 34* F.
 

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Discussion Starter #7
I recently replaced the compressor and such, so the system's only been working now for about two months. It takes about 30 seconds or so for the air to go from searing hot to chilly (when the car's been baking in the hot sun all day).
 

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if you have to keep recharging your a/c system, then you have a leak....no other way around it.
Freon in any shape or form, does not wear out....only parts in the system do(i.e. compressor, seals, etc).
 

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Discussion Starter #9
Yeah, having a leak is possible. I'll know when I take it to the place that charged it because I bought the 6 month free leak detection warranty with the fill. Although when they pulled the vacuum they said it held it for over an hour, so... we'll see. I'm not even sure if the system is leaking, because the way it behaves now is the way it was right after I had it charged. :confused:
 

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Too bad you have a 97. 96 and earlier cars had an adjustable A/C cycling switch. You could set it to around 18-20 psi on the low-side to cut out and the discharge temps would be in the low 30's. It may just be that your cycling switch is not letting the system get cold enough as you like it. That doesn't mean the switch is bad, just that it doesn't go that low.
 

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It's not typical. Had the same charge in my 3.8L system for 7 years. Blew cold instantly and stayed like that as long as it was on. Didn't matter how hot it would get outside, it would still have discharge temps out of the center outlet at around 34* F.
Hmmm, interesting.... Then again the previous time I filled my system, I didn't fully charge it because I didn't know any better. It blows much cooler faster now that it is fully charged. Every 30K miles sound about right for a freon refill?
 

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Discussion Starter #12 (Edited)
Chris, I was just about to ask you about the cycling switch adjustment since I've seen you mention it a few times. I did see that the switch's pressures were a tad higher than the stock rated pressures when I bought it... 18/38 PSI or so is it? Maybe I can find a good used one and try that out to see what happens. From my thread about replacing the compressor, it looks like the new cycling switch is designed to keep the pressures between 24 and 44 PSI. The lower the pressure on the low side, the colder it should get, right? I'm starting to think that's why it's not as cold as it could be, it makes sense to me.
 

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Every 30K miles sound about right for a freon refill?
No, that's not right. Infinity miles is the interval for refrigerant refills unless the system has a problem, at which point it needs to be addressed until the system no longer needs service. As it was mentioned before, there is nothing flowing through the system that wears out. The refrigerant and oil do not start degrading to the point that they need to be changed. The refrigerant and oil will last much longer than any of the individual system components does.
 

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Chris, I was just about to ask you about the cycling switch adjustment since I've seen you mention it a few times. I did see that the switch's pressures were a tad higher than the stock rated pressures when I bought it... 18/38 PSI or so is it? Maybe I can find a good used one and try that out to see what happens. From my thread about replacing the compressor, it looks like the new cycling switch is designed to keep the pressures between 24 and 44 PSI. The lower the pressure on the low side, the colder it should get, right? I'm starting to think that's why it's not as cold as it could be, it makes sense to me.
The pressures you have are within range of the specified pressures for the low-side. I believe the stock spec is 18-28 for the cut-off. Each switch will probably vary a little, but yes the lower the pressure the colder it gets until the system ices over and air can't flow across the evaporator.
 

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Discussion Starter #15
Yeah, the extra 6-14 PSI... that'd be why I'm not as cold as I'd like to be. New (old) cycling switch is now on the menu.
 

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No, that's not right. Infinity miles is the interval for refrigerant refills unless the system has a problem, at which point it needs to be addressed until the system no longer needs service. As it was mentioned before, there is nothing flowing through the system that wears out. The refrigerant and oil do not start degrading to the point that they need to be changed. The refrigerant and oil will last much longer than any of the individual system components does.
I think you have me wrong. I didn't mean a full change in freon like an engine oil change, I just meant when you would probably need to add more freon. I know freon is not one of those things that degrade like engine oil. Will some freon be released over time though? Through the fittings and such.
 

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Again, unless the system has a problem, the A/C will NEVER need service. Another way to say this is that if the system doesn't have any problems (and this includes leaks, since even the slightest leak is a problem), the system will never need to be recharged, serviced, or refrigerant added.
 

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Discussion Starter #20
Master is right - The A/C system is built and charged for life. Like he said, unless there's a problem (like a toasted compressor or leak), you should never have to do anything to the system. My dad recently bought an old 88 Eldorado - a/c never serviced and still works just fine. It's extraordinary because leaks develop and compressors fail... but it's not abnormal.
 
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