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Old 08-28-2017, 09:22 PM   #221
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I'm using this chart: http://acprocold.com/faq/r-134a-system-pressure-chart/

My infrared thermometer aimed at a plastic container IV the shade says it is 89 degrees outside.

I adjusted my rear system so that the high side is reading 270 and the low side is reading about 43.

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Old 08-28-2017, 09:35 PM   #222
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if you look at the inner rings of the gauges.. you'll see little numbers.. one of those rings will be R-134a.. those numbers are temperatures.. the blue gauge is the suction pressure and so you need the evaporation temperature of the freon.. its hard to get exact.. but you can take the temperature just past the expansion valve (often you have ot take the cover off the inside unit). and then take the temperature of the big pipe as it exits the evaporator.. avg the 2 numbers and its a good guess.. (should be done with engine RPM at 1000-1200 and fans on high..

then outside take the Inlet temperature of the condensor.. and the outlet temperature of the condensor and average those 2 numbers.. and those are the temperatures (inner ring numbers) you shoot for.. or close...

most typically your high side will be 150-200 PSI. and your low side will be 20-40 PSI.

the lower numbers seen when its cooler outside ( and cooler in the bus).. the higher numbers seen when its warmer..

I dont like to charge an A/C below 70 outside temp.. its tricky and easy to over-charge.. 80-90 is perfect outside tmep to work with.. I usually error on the slightly under-charged rather than over-charged.. unless I know im chargimng a system with a slow leak (never should do this!!!) .

when just checking a system.. let your system run for 5 minutes or so before determining its low or not.. it needs to circulate and take care of the initial high heat loads and initial warm up / cool down of the metals in the coils and get the oil flowing..

some tips about those gauges.. they have valves on the end of the hose and also on the body.. make sure all valves are closed and hoses are tight when you install the gauges..

you'll need to get a can tap that has a removeable or hose.. or no hose so you can use the manifold gauges to charge your system. (can will go on the yellow center hose).

open just the valves at the A/C fittings to visualize pressure but the manifolds should be closed. you'll see your respective pressures...

to charge, install a can onto the yellow hose and open its valve.. slowly crack open the BLUE low pressure manifold valve to add freon.. you'll see the blue gauge go up and may see freon in the gauge window. . you DONT want to blast it with liquid.. so if you see liquid in that window either turn your can right side up **OR** way i do it is to just crack open the blue valve.. and you'll notice that the hose gets cold..thats good it means you are evaporating the liquid from the gauges to a gas as it goes in..

charging can upside down gets you liquid that you can bleed in, charging right side up gets gas direct from can.. it will start out chargong fast with gas but as the can gets cold it will slow way down to where you think the can is empty.. but its not until its warm.

finish a can, be sure manifold valves are closed and add next can..

if you are really close to where you want to be in the middle of a can, close the Can valve... then open the blue valve to clear the yellow hose of any freon.. leave the can valve closed..

these long hoses tend to hold a bit of freon.. esp the red one as it may be liquid in there.. we need to clear that hose before you remove it.. so Close the red valve on the end of the hose (at the A/C fitting on the bus)...

the Can valve MUST BE CLOSED!!

now open the blue valve at the manifold.. and then slowly crack open the red valve and empty the red hose.. you'll know when its empty as the pressure on your red and blue gauges will go the same.. (your red valve was closed at the A/C fitting)..

what you just did was take the freon in the red hose and empty it right back into the A/C.. its an ounce or so max so wont cause an overcharge on a system that big.. and will prevent hand burns when putting your gauges away

close both manifold valves. and the blue A/C fitting valve (all valves whould be closed).. remove gauges and slowly take apart the hoses.. they will hiss theres a little freon left in the hoses..

hope I dont confuse you too much..
-Christopher
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Old 08-28-2017, 09:50 PM   #223
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In case it isn't obvious I'm mostly making it up as I go.

I'm not sure in Reading these dials right for the pressures for temperatures. For sure I have no idea what the evaporation temperature is of the refrigerant. The chart I find for the high pressure side send completely at odds with what I think the dial reads... The dial seems to suggest I need about 100 psi at 90 degrees, the chart says 250. Am I reading it wrong?


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Old 08-28-2017, 10:18 PM   #224
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90 degrees freon temperature is what that inner chart is.. so if your condesning refrigerant temp is 100. your gauge would read right about 125 psi... the chart you are reading is likely suggesting how hot it is outside..

so if you measured the pipe going into the condensor underneath (pretty hot).. and measured the pipe coming out of the condensor (should be warm but not hot). and took the average of the 2 numbers.. ie 150f going in and 100f coming out. average 125, youd expect to see a gauge of about 170...

charghing by low side is a little easier. as most often you are looking for low side pressures of 20-40. (sometimes a bit higher on a really hot day)... (after your sysyem runs for 5-10 minutes and starts to cool the inside down a bit).

your suction pipe should get pretty cold.

there are plenty of people out there that charge the A/C till the suction line is beer can cold and call it a day...
-Christopher

250 is a bit high for even a 90 degree day. on a 90 degree outside temp day you could see 250 if your condensor isnt running efficiently or if its a bit overloaded - ie dirty coils, not fully functional fans... but id likely expect to see more like 200-220.. its tough to use outside temperature and get a good charge..

maybe im too much a perfectionist when it comes to A/C.. lol..
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Old 08-28-2017, 10:22 PM   #225
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Well I messed with the front one some more and even after messing with pressures or doesn't want to keep running more than about 15 seconds. I'm going to call it dead until I can get somewhere long enough to fix it.

I burned my hands on the high pressure line so it might be a day or two before I'm ready to grab one of them again. Also the fitting on the high pressure line may be leaking.

Whatever I have driving to do!

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Old 08-28-2017, 10:27 PM   #226
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the high pressure line from the compressor is normally hot.. the one to think about is the one that comes FROM the condensor coil headed out to the indoor unit..

what pressures did you have on the front one? sounds like its eoither tripping on low or high pressure.. they will short cycle
-Christopher
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Old 08-29-2017, 05:49 PM   #227
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Quote:
Originally Posted by brokedown View Post
That's our tandem kayak which hasn't been off the roof since Kansas....
Not a lot of call for kayaks in Kansas, one would think.

I got excited for a moment there; it looked like a hang glider if you squint.
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Old 08-29-2017, 06:09 PM   #228
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Originally Posted by dan-fox View Post
Not a lot of call for kayaks in Kansas, one would think.

I got excited for a moment there; it looked like a hang glider if you squint.
Huh, when I squint I see Marilyn Monroe on the roof.

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Old 08-30-2017, 04:58 PM   #229
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Well this morning my other compressor decided it was done, and then there was none. I've been calling around all morning looking to see if anyone near here can help me out in the reasonably near future and it seems like I'm going to replace them myself.

I'm not sure if the replacement i did died because I did it wrong or if it died because it was cheap autozone crap... And if it was my fault, I don't really want to spend $900 on new Sanden compressors just to have them die in 2 months because I ruined them. I can get a pair of remans from Amazon for about $250, which is less than I paid for one at autozone.... Dang it!
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Old 08-30-2017, 05:35 PM   #230
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I just ordered a pair of compressors with next day delivery. I need to get a can valve, a bunch of refrigerant, and some compressor oil this evening. PNW_Steve is providing an area to work, a vacuum pump, and moral support.
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