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More Questions on Proper Charging Amount

uunfews on Thu August 21, 2008 1:03 AM User is offline

Year: 2001
Make: Honda
Model: Civic
Engine Size: 1.7
Refrigerant Type: 134a
Ambient Temp: n/a
Pressure Low: n/a
Pressure High: n/a
Country of Origin: United States

Hi,

I am still contemplating my own AC repair and have rented this manifold gauge set SKU 7 00376-89772 2 made by Mastercool and I have more questions regarding charging the system to the oem capacity by weight. My car's specification (01 Honda Civic 4dr LX) called for 17.6-19.4oz of r134a.

I have read this article I found on the net and based on that I have some addl questions for you working pros http://www.4s.com/fourseasons/tech_tips/tech_tips_english/ab326.html.

What I like to know is seeing that my yellow charging hose is 72" long then would the freeon that gets left behind in this long hose be more or less than the 2oz that the article suggested? Mastercool make hoses in 3 lengths - 36", 60" and 72". Mine is 72". Also do I add in 2oz extra for hose compensation every time a new can is hooked up to the charging hose since disconnecting the hose for the can in between switch out would allow the amount in the hose to flow backward and out if I don't have a can tap. What if I have a can tap in between the yellow hose and the can? Would a can tap prevent this backward flow when the previous can is taken off ? So then would the total be 2oz total to be added onto or 4oz total since I will be using 2 cans. I plan on putting a digital scale on the bottom of the can after warming the can to 120 F and metering it in. Do you think this will work.

My math for requiring 2 cans is this 19.4 oz+0.5 left in first can with temperature of 120F+0.5 oz left in second can with temperature of 120F+2 oz for hose loss from first can+2oz for hose loss from second can=24.5 oz total. I would need 2 cans so I would have 24oz and be .4 oz short but OEM calls for 17.6-19.4oz total so I should be ok. Is my math off?


Thank you in for your advice in this matter. I like to get the exact charge into my ac system as best possible with the limited resources that I have and any tips you can provide is much appreciated.

Thanksssssss!!!





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Newbie wanting to learn how to fix his 01 Civic AC in this freaking hot Dallas TX area.

mk378 on Thu August 21, 2008 9:10 AM User is offline

Two whole cans will be too much. Hose loss is not that large, it can be practiaclly nil if you do it right.

That gauge set should have a self-closing isolation valve on the can end of the yellow hose. This will trap all the refrigerant in the hose so there is basically no loss when switching cans.

After charging, clear the manifold of the liquid refrigerant that will be in the red hose. Disconnect the red hose from the car, disconnect the yellow hose from the can, and with the compressor still running, open both valves (safe to do because the high pressure is no longer hooked up). This will clear nearly all of the refrigerant out of the hoses and manifold and into the low side of the car, leaving only a little gas behind. This amount of gas is less than the 1/4to 1/2 oz of gas that must be left behind in an "empty" can because the volume of the hoses manifold and gauges is much smaller than a can.

So you should leave some behind in the second can, about 4 oz. Also if you don't have UV dye in the system now, it can be simply added by using a can of R-134a plus UV dye as the first can when you charge.

uunfews on Mon August 25, 2008 3:20 PM User is offline

Quote
Originally posted by: mk378
Two whole cans will be too much. Hose loss is not that large, it can be practiaclly nil if you do it right.



That gauge set should have a self-closing isolation valve on the can end of the yellow hose. This will trap all the refrigerant in the hose so there is basically no loss when switching cans.

Yes it seems to have a one-way valve but I am not sure. I hook up all the lines to the gauge , 90 degree low high and low side couplers to the hose ends and the yellow hose to the vaccumm pump. I pulled a vaccum and disconnected the yellow hose from the pump and the gauge retained the vaccumm. So does that mean I have a self closing isolation valve you mentioned? I wouldn't have to purge the air in the yellow hose in this case then right?



After charging, clear the manifold of the liquid refrigerant that will be in the red hose. Disconnect the red hose from the car, disconnect the yellow hose from the can, and with the compressor still running, open both valves (safe to do because the high pressure is no longer hooked up). This will clear nearly all of the refrigerant out of the hoses and manifold and into the low side of the car, leaving only a little gas behind. This amount of gas is less than the 1/4to 1/2 oz of gas that must be left behind in an "empty" can because the volume of the hoses manifold and gauges is much smaller than a can.

I am not too clear on this instruction of yours. So I disconnect the high side hose from the car high side port and yellow hose from the can's end. But you suggested to open up both high and low side at the manifold. Wouldn't this let more additional refrigerant to flow into the high side hose with the compressor running till it equalizes the low side pressure of 30-45-50psi???? Wouldn't it be better to keep the high side valve closed so the freeon wouldn't bleed over? Unless you are assuming I am charging with lidquid hence you mentioning opening up the high side?

Signed,

Confused??????????????

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Newbie wanting to learn how to fix his 01 Civic AC in this freaking hot Dallas TX area.

Edited: Mon August 25, 2008 at 3:20 PM by uunfews

mk378 on Mon August 25, 2008 3:31 PM User is offline

After running the car with gauges connected, you will have about 200 psi (or whatever your high pressure is) in the high side hose, and typically it's all liquid. The refrigerant condenses in the hose and gauge because it's cooler than any other part on the high side.

So the procedure is to drop everything down to low side pressure, returning most of the trapped refrigerant to the car.

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