Farm Equipment - 6080 AC

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6080 AC

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=30278
Printed Date: 06 Mar 2025 at 3:33am
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Topic: 6080 AC

Posted By: walkerb
Subject: 6080 AC
Date Posted: 05 May 2011 at 3:55pm

What is the pressure for the air conditioner gas.Had it recharged today and my mechanic wondered what the correct pressure setting should be?

Replies:

Posted By: tbran
Date Posted: 05 May 2011 at 4:29pm

if you are useing R134a we have found 210# on high on 80 degree day and somewhere around 15-18 on the low side. Add a pound per degree on the high side like on a 90 degree day 220# and 95 225# . Low should be the same - it will not vary much. Now close the cab door and put blower on low speed and watch low pressure - it should go down to about 9# before the thermostat kicks out the clutch. Should freeze your latisicals off. Watch on these units as we have had calls where it cooled great but then quit cooling and after sitting it cooled fine again for a while. Found core partially plugged and the condensor core was freezing or frosting over and thus blocking air flow and heat absorbtion. When it melted it ran great again. Sometimes it has been necessary to turn thermostat down on cool humid days if the fan is run on low.

Posted By: wekracer
Date Posted: 05 May 2011 at 6:00pm

thanks for that info. we have been having trouble getting ours set right and i'm sure it has to do with the temp we have been charging.

Posted By: Hurst
Date Posted: 05 May 2011 at 6:06pm

I forget what RPMs you're supposed to have it running to charge the pressures, but I know my 7000's service manual specified a minimum engine speed to check. Maybe someone else can chime in. I want to think it was like at least 1500 rpms.

Hurst

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1979 Allis Chalmers 7000
5800 Hours

Posted By: dave63
Date Posted: 05 May 2011 at 6:18pm

tbran , I think you are refering to the Evaporator not the condensor.

the condensor is outside the evaporator is in the cab. Few peaple realise the impartance of proper air flow through the evaporator and the condensor. frozen and cloged evaporators cause liquid refrigerant floodback to the compressor that can ruin it. and clogged condensor will cause high head preasure also hard on the system and makeing it inpossable to properly charge the system.

You are right on with your preasure and temps.

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The universal answer to all questions is yes, how much do you want to spend?

Posted By: cms
Date Posted: 06 May 2011 at 9:27am

Dont you want the Low side pressure to be around 40 degrees or 35psig for R134a? At school we charge all house ac this way on a hot day but we use R22 or R410a. When ever you go to Walmart they sell car charging kits and the gauge shows that you are in the good range at around 40 degrees. Was just wondering what was the right way. So far have charged 9170 Deutz Allis and 1586 this way with no problem and they are cold?

Posted By: dave63
Date Posted: 06 May 2011 at 9:57am

The agco service manuals have a chart for charging by head preasure rather than suction preasure.

So they seem to be more concerned with head superheat than suction superheat. I think you will find that if you get your head preasure in that range your evaporator temp. will come down to the 30-35 deg. range. Keep in mind on the 134A conversions the condensor may be slightly undersized therefore your suction superheat may never be ideal. The walmart charging kits have caused more compressor failure than most people know about becouse most people ASSUME that the problem is low charge but when there is a blockage like poor condensor air flow or a cloged drier suction preasure will be low.

Its nice to have people ask about this instead of messing up a system.

Even commercial and residential AC it is important to watch head preasure. But we typicly charge by evaporator superheat.

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The universal answer to all questions is yes, how much do you want to spend?

Posted By: cms
Date Posted: 06 May 2011 at 12:46pm

Can you post the charging chart from the agco manuals or show a link so i can see it. Is 30 over ambient still a good rule for condenser (High side) pressure? Thanks for the help just finishing up my two years at trade school for HVAC, we did not learn about charging automobiles.

Posted By: dave63
Date Posted: 06 May 2011 at 5:40pm

I will see what i can do, i am better at HVACR than computer stuff but i like to learn.

Give me a few days to get it together.

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The universal answer to all questions is yes, how much do you want to spend?