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AC recharging question
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nosoup4u
Posted 6/24/2016 19:39 (#5373991)
Subject: AC recharging question


I replaced the old compressor on my John Deere 6620 with a new Seltec along with the expansion valve and receiver dryer. Ran a vacuum on it for little over an hour. Shut off the pump and let it set for a half hour and vacuum held.
Started charging process. Low side valve open, high side shut. Engine running at 2000 rpm. It sucked the first can down in about two minutes, fast enough that the can got cold in my hand. Added three more 12ounce cans and it took probably five to ten minutes each. Never fast enough to make the can cold. The low and high side pressure are right around 100 psi.
Capacity is supposed the be 64 ounces.
Should both pressures be the same at this point or is it because the high side is closed. Should the low side be getting lower by now or is 100 normal at about .65 per cent charged?
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J.L.
Posted 6/24/2016 19:50 (#5374007 - in reply to #5373991)
Subject: RE: AC recharging question


Iowa
I'm no expert but if the low and high side stay the same with the system on, my first guess is the clutch is not engaged on the compressor. Normal for me is like 10 psi on the low side/ 150 psi + on the high side give or take.
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1448
Posted 6/24/2016 20:00 (#5374022 - in reply to #5374007)
Subject: RE: AC recharging question


s.w. IA
Low pressure cutout may have disengaged your clutch, Might have to use a jumper wire to engage clutch. Pressures don't sound right.

Edited by 1448 6/24/2016 20:03
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cottonhauler
Posted 6/24/2016 20:37 (#5374086 - in reply to #5374022)
Subject: RE: AC recharging question


Zabcikville, TX
Run your engine at 1100-1200. 250 on the high side is a good indicator. A JD mechanic told me once, twice ambient (outside) temp + 40lbs is where he charges to. I trust this guy, he knows his stuff. Now, this is general. NEVER (or at least I don't) open the high side while hooked to a can or the bottle is open. I've seen them explode, it ain't pretty. High side should go up while low side goes down. In my experience (and I went to school for diesel mechanics, A/C included) there is no correlation between high and low pressures. I always look at high side, that's what'll blow lines and cause grief down the road. Matter of fact, we had a JD 8530 not cooling well just a couple weeks ago. I added freon for the first time in 4 years since owning the tractor. Bossman calls and asked "what did you do to the A/C?" It's hot in here! I got un-busy and checked it out. Turns out when I charged it, it was 85 degrees outside. At 95+ degrees, the pressure (high side) got too high and wouldn't let the compressor cycle like it's supposed to. I let some out, checking gauges all the while, and voila!!!!!!! It started cooling. No problem with the system, just overcharged. A/C is a science, each system is different, and will run different pressures on low/high side. If converting from R-12 to 134A, leave bubbles in the sight glass on the receiver/dryer. Engine at 1100-1200, fan in high, all doors open on cab.

Edited by cottonhauler 6/24/2016 20:38
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3furrow
Posted 6/24/2016 20:35 (#5374083 - in reply to #5373991)
Subject: RE: AC recharging question


suburb of Ontario`s Middle east
Pressures are not right. At 100 psi on low side u getting ready to turn that can into shrapnel. If it is one of those puncture top cans you are outside its abilities. There is no way it is taking product with a low side of 100.
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Sodbustr
Posted 6/24/2016 20:40 (#5374090 - in reply to #5374083)
Subject: RE: AC recharging question


Western Iowa
I agree, a little dangerous.

Compressor isn't working if your high and low gauges are both at 100. I hope you know to run a jumper wire to the compressor?

It shouldn't take 2 minutes EVER to put a 12oz can in..... empty or full system.
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KelB
Posted 6/24/2016 21:03 (#5374144 - in reply to #5373991)
Subject: RE: AC recharging question



Ayr Queensland Australia 4807
I alway add the first amount of liquid on the high side without the compressor running then meter in the liquid not exceeding 40 psi on the suction side.adding too much on the low side can cause an issue for the durability of the compressor. pressures should be low side should be at 10% 15 psi low side 150 psi high side ensure condensor and evaporator are spotless ,also check voltage at the compressor while machine is running.
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AGDEAL
Posted 6/24/2016 21:29 (#5374194 - in reply to #5373991)
Subject: RE: AC recharging question


Illinois
The psi you are reading right now is actually your ambient temp. Both sides will read ambient temp when "off". Your system is "off " because of the high and low pressure switches.

As other said you need to jump a wire to your compressor.
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ccjersey
Posted 6/24/2016 21:32 (#5374200 - in reply to #5373991)
Subject: RE: AC recharging question


Faunsdale, AL
High side valve on manifold does NOT need to be open to get a gauge reading.

However, the hose couplers do need to be connected correctly and opened if they are the type with a screw-in knob to open the valve in the port.

The ones I am thinking of have to be screwed in/tightened down to open the port and lock the coupler onto it.

Like several folks have already pointed out, it is likely the clutch is disengaged so pressures have equalized in the system. Need to see why it is disengaged and fix it. With 100 psi on high and low, both pressure switches should be closed enabling clutch to pull in. What about the thermostat in the cab? Check for voltage into and out of it. Have seen the fan switch be burned up and fan still run but not sending power out to thermostat to engage clutch. Once in a blue moon the thermostat itself is bad in my experience.

Edited by ccjersey 6/24/2016 21:36
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nosoup4u
Posted 6/24/2016 21:37 (#5374211 - in reply to #5374200)
Subject: RE: AC recharging question


I suppose to run a jumper wire I go from the positive terminal on the battery to the wire that goes to the clutch? At what point do I remove it?
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J.L.
Posted 6/24/2016 22:03 (#5374259 - in reply to #5374211)
Subject: RE: AC recharging question


Iowa
The idea of the jumper is to bypass the low pressure switch to get the compressor to run to start sucking in freon into an empty system. Otherwise the low pressure switch kicks out the compressor right away and makes it difficult to charge the system. If you have four cans in already I doubt you need to do this but you can to see if the compressor will come on to help diagnose.

I've never touched a 6620 but am going to assume there is an on/off switch of some sort, thermostat, low pressure switch, and high pressure switch that all need to be closed to send voltage to your compressor clutch.

I'd take a meter or test light and see if your getting voltage at the compressor and work backwards to find a problem if you can't get voltage to the compressor clutch.

Edited by J.L. 6/24/2016 22:16
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bankshotone
Posted 6/24/2016 21:41 (#5374224 - in reply to #5373991)
Subject: RE: AC recharging question


Central Iowa
Were you holding the can upside-down?
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eight
Posted 6/25/2016 00:31 (#5374421 - in reply to #5373991)
Subject: RE: AC recharging question


South Texas
Can't say 100%, but don't think there is a high or low switch on a 6620.
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coastalBend
Posted 6/25/2016 05:03 (#5374459 - in reply to #5373991)
Subject: RE: AC recharging question


south texas
If you did an ap conversation, and only added the high pressure cycle switch the comp should engage upon turning ac on.

To check clutch
see if it will spin with all electronic off (it should )
turn on key, dont start
turn on ac blower and thermo to max cold
clutch should not spin now since belt is on pully

if it spins you dont have 12v to clutch, no low side switch on 6620 unless u added it.

like others said be sure the high side gauge manifold valve is closed. Both quick couplers need to be cliped on and those valves open.

i fine tune my ac at running speed of engine, u can get it real close at idle.

In my area 225 is about the lowest high side pressure we can achieve. 90-100f with 60-100% humidity.
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