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Old 06-08-2014, 01:52 AM   #1
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Default Air Conditioning Concern in Mom'* '95 Blazer

The A/C has always been weird on this truck, and I think I finally got a handle on it, but need some help.

I flipped the A/C on (100*, 10% humidity), and found the compressor making bad noises, and pressures at 300psi High, 60psi Low. I picked up the engine speed, and saw pressures push higher, then dropped until the compressor kicked out when the low side cutout was reached at 25psi. I added a can of refrigerant at this point, hoping for the best. After the can was in, the pressures pushed even higher, 360psi high, 80 psi low, and the compressor making a horrendous racket. Picked up the engine speed again, pressures fell right in line, and the compressor shut right up. Let off, and pressure shoots up again, noise returns.

So, what'* going on? It'* as if the condenser is not shedding enough heat at idle is my guess, but not sure why. Is there supposed to be a way that the clutch gets locked when the A/C is on? At 210, I can hear the fan mighty loud, so I imagine the thermo side of the clutch is working fine.
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Old 06-08-2014, 09:03 AM   #2
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My guess is that your condenser is not cooling properly. If you cold water mist spray the condenser, and then notice the psi dramatically drop, I think u found the culprit.

Last edited by Soft Ride; 06-08-2014 at 09:05 AM.
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Old 06-08-2014, 11:49 AM   #3
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But is pressure building up because there isn't sufficient air flow?

Could be debris in front of the condenser, or that fan clutch is slipping and not drawing enough heat from the condenser....
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Old 06-08-2014, 07:27 PM   #4
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I think you both may be right. I will probably pull the front grill off and clean up in there. Mommy also has trouble with one headlight going out when it rains, so I can fix that when I am in there.
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Old 06-09-2014, 07:54 AM   #5
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if the condensor has never been cleaned this is likely the issue. we have real bad pollen here and i have to clean the bonnies rad and cond. every other year or so or it will start not cooling well and the engine temp starts getting bad. i take the rad fans out and use foaming simple green on both sides and rinse with a hose. a couple times till clean water comes through the front from the back
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Old 06-21-2014, 01:11 AM   #6
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Part 2: The solution

I took a look at this video on youtube:


The recommended product:
Nu-Calgon 4291-08 Nu-Brite Coil Cleaner - 1 Gallon, Blue: Ac Condenser Cleaner: Amazon.com: Industrial & Scientific Nu-Calgon 4291-08 Nu-Brite Coil Cleaner - 1 Gallon, Blue: Ac Condenser Cleaner: Amazon.com: Industrial & Scientific

I moseyed on down to my local A/C supply store, picked up a gallon for $29.99 + tax, got the truck, and loaded up a 20 oz spray bottle with a 4:1 mix, and went to town after pulling the front grill off (the sound of plastic snapping is a wonderful thing BTW).

The condenser:
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Everything was soaked in ick. Looking closely, it was almost as if someone drove through a wall of giant flying ants at speed. Also the condenser is painted black, but only on the front side (doesn't look stock, but I could be wrong). Some stuff was stuck in between the radiator and condenser as well. I got as many chunks as I could out with the hose, and started spraying the cleaner. Most of the 20oz bottle went down. They are dead right about this requiring ventilation. It was killing me, and I was factoring the breeze in my favor too.

Engage foaming action:

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Look at all that crusty yum!

I got everything rinsed and back together, only to find low pressures all around. Pop the gauges off, to find leaky valves. One service kit laater, and pressures fell in line, with the lowest pressure at idle. Compressor still is making a racket at idle, but it doesn't sound so distressed anymore. I am concerned it may be slightly overcharged right now, but I will likely check it tomorrow once it gets good and warm. The sun went down and the temp dropped very quickly on me so the A/C dropped off, but it looks like it'* fixed.

I now have a lifetime supply of condenser cleaner still too
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Air Conditioning Concern in Mom's '95 Blazer-wp_20140620_17_34_27_pro.jpg   Air Conditioning Concern in Mom's '95 Blazer-wp_20140620_18_00_39_pro.jpg  
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Old 06-21-2014, 09:04 AM   #7
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i wouldnt do any of that, the stuff they use at the a/c store is way to caustic to people and paint. we got a little one time on some other stuff and it ruined it. if you put this on your car it will ruin what ever painted stuff it runs on to and you have to worry about were it drains to etc.. its a whole unnecessary debacle. and if you clean it from the front only the front get cleaned, been there many times, they HAVE to be washed from the back forward to get everything and foaming simple green is good enough most times. you may have gotten lucky and only had stuff on the face but its more luck than standard good practice.

when i am working on commercial a/c they have come out with a new biodegradable coil cleaner in gallons so you dont have to worry about where it goes, but its still caustic and it eats the plastic sprayer and paint off the units.

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Old 06-21-2014, 10:24 AM   #8
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Originally Posted by jwfirebird View Post
i wouldnt do any of that, the stuff they use at the a/c store is way to caustic to people and paint. we got a little one time on some other stuff and it ruined it. if you put this on your car it will ruin what ever painted stuff it runs on to and you have to worry about were it drains to etc.. its a whole unnecessary debacle. and if you clean it from the front only the front get cleaned, been there many times, they HAVE to be washed from the back forward to get everything and foaming simple green is good enough most times. you may have gotten lucky and only had stuff on the face but its more luck than standard good practice.

when i am working on commercial a/c they have come out with a new biodegradable coil cleaner in gallons so you dont have to worry about where it goes, but its still caustic and it eats the plastic sprayer and paint off the units.
You may have a valid point, as this is some serious stuff, but it also seems like simple green would not have been strong enough to cut it. In my forum years I don't ever remember seeing a write-up on cleaning condensers, so we could probably use one.
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Old 06-21-2014, 01:21 PM   #9
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the cars i have you can tilt the rad back and get enough room to clean both the condenser after you take the fans out. im not sure about any other cars so i dont know about how a universal write up would go. simple green does work well though i use it in my atv rads too and they get so clogged with mud and pollen the hose barley gets through at first normally when they are that bad you have to do it twice, but even if you do it doesnt melt plastic or burn your skin when you accidentally get some on you. and you dont have to dress like a bee keeper to use it
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Old 06-21-2014, 03:50 PM   #10
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Seen that video myself a few days ago, Justin has valid points, it is very caustic since it is a high alkaline based cleaner, but it is said to be biodegradable, almost all of their products are said to be biodegradable, not sure about the Cal-Brite though..
http://www.trane.com/commercial/Uplo...-prc020-en.pdf

If any do this wear gloves, safety glasses, some old thick clothing, and be careful spraying it on, it can and will strip paint, but if you are only spraying it on the condenser, I don't see how you are going to get it on the cars paint job, unless you are careless when you rinse it.

Of course if you are not really careful, and you left that stuff on the coils for too long, then I am pretty sure you could risk damaging them, so it would be best to have the refrigerant evacuated from the system, remove the radiator, and condenser, clean it, and rinse it thoroughly, put it back, and recharge the system, of course most cannot do this because those machines used to evacuate the refrigerant are expensive, what I am getting at is it would be better left to the professionals even though it may be expensive.
It should not need to be done but every couple of years anyway.
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