7330 a/c

Can some one tell me the pressures high and low on my 7330 what they should be br>I'm having trouble with my ac the tractor just turned 500 hrs
So would you think the dryer or expansion valve could be stopped up
My pressures are 25-28 ,125-130
And the low pressure line is freezing up
Have all 4 new cab filters
Can't figure it out worked good last year
Do I need to vacuum it and start over
If so how much does this system hold
Thank you for any help

With the air off both pressures should be equal at about the outdoor temp so 70 degrees would be about 70 lbs. You could be just a little low on r 134.

Ignore the low pressure line frost until it gets really, really HOT outside because they all do that when it's mild weather so it's not a real indicator at this time of year. You do not need to vacuum and start over, as long as you have pressure, water can't get in and vacuum is only needed to get rid of water within the system. Since you have an expansion valve, running pressures mean very little unless they are red flag high and those pressures are fine, 250 is too high. You will want a running low pressure just above 30 PSI with 134a keeping in mind gauge sets can be inaccurate and show a few pounds high or low easily. 35 PSI would be the upper limit for low side if I'm doing it - that's 40 degrees inside the evaporator. The real test is if the evaporator freezes up such as to not allow full air flow thru it. I prefer this marginally low on freon set up as I can just shut off only the compressor to defrost it from the cab when that becomes a problem. I also then know exactly that I'm a little low on freon by this symptom, put one more can of freon in it and it won't freeze up, but you may not like the slightly warmer air produced from the evaporator.

Very easy to figure out when you know that 90% of systems leak a small amount at the front compressor seal AND it worked fine last year - you simply need to try adding a can of freon and see if that doesn't work a whole lot better. You may put in up to two cans of freon to be safe about this without worry on tractor sized systems, but do stop at one can first and test it for a few days of work. Do NOT put stop leak in it thinking this can fix the carbon/ceramic front seal leak, it can't and won't, but it will cause your entire system to require a complete and totally new parts change out including ALL hoses if you expose any part of it to air. Stop leak for AC systems should be outlawed.

I do not think the dryer or expansion valve is stopped up as they typically only do that when the compressor has cratered itself and is locked up entirely or the system has had disconnected hoses for extended time allowing dust, water and resulting rust direct access inside the system. I have no idea how much freon/oil that tractor holds, but your dealer should be able to look it up. I'm pretty sure one can of freon will put you right again.

mhudgins
I also think the AC system pressures are low requiring adding some refrigerant. Depending on ambient temp I get high side up to about 175 psi

Are you SURE it isn't an airflow issue, mouse or other debris stopping airflow to part of the evaporator, or one of the two fans not running for some reason?

I agree with this 100% but I have found in situations like yours that abt. 4-6 ounces will work for a really cold system . But you must have air-flow.
Here's some approximate pressures : outside temp. 70*- should see 135-170 psi on high side , low side at that temp 22-28 lbs.
outside temp 80* 155-200 psi. on high side , low side abt. 22-29 psi.
90* high side 200-245 psi. low side 26-35 psi. Air temp on inside air ducts abt.40 degrees . My friend that schooled me was an old refrigerator man and he said if you can drop 20* from out side temp. at 90* you have a good a/c system . At 90* fans will need to be on high . Hope this helps .

Added a can got 25-28 low side
175 on the high side
Duct temp won't get below 55
It was 72 outside when I did this
So I'm going to run it a couple of days see what it does
55 is ok right now just don't know about a 90 day
Thank everyone for there input I would be lost without this forum and its members

Also make sure your water valve is shut off.

Well I have run my tractor for a few hours and it's still not getting cold
Starts off cool the gets warmer 55 is as cold as it gets
Have check air flow in and around evaporator nothing in the way
Vacuumed the system no leaks holds vacuum overnight
Fill it back with 3lbs 4oz of freon and 4 oz of oil
Still nothing
But after running for a couple hours middle of compressor is froze and low side line is frozen solid not frosted but frozen
Does anyone think my compressor could be weak
But other than that I can't think of anything else

That was the recommended amount from my dealer on the freon and oil

[qu04/27/16) Well I have run my tractor for a few hours and it's still not getting cold Fill it back with 3lbs 4oz of freon and 4 oz of oil
[/quote]

Did you flush oil the last time before vacuuming system? If not you probably have too much oil in system.

Did you ever check to be sure heater valve is shutting off coolant circulation through heater core when heater isn't being operated??

So it looks like one can was not enough, but I did say you could try two. Did you?

Did you loose 4 oz of oil at any time? I suspect pretty much none to a few drops so now you have twice as much oil in it as it should have? In other words, did I understand that part right? What was your low side pressure and evaporator temp when running the full charge?

You did good reporting that vital information with one can in, you should have done the same for two cans added as well and then nothing of the kind is reported for the full charge except the excess frosting issue extending into the middle of the compressor as a new symptom.

You don't seem to know whats important. You seem to be doing only what you want and ignoring advice.
Take it to professional unless a whole lot of common sense starts working there.

For example,
What type and viscosity of oil did you put in it because this information is vitally important. You don't mention it at all as if it isn't critical and it very much IS.

Double dose of oil might be responsible for excess frosting issues now, would have been much better without the full charge of both oil and freon added. You might also have just added 52 oz of freon to the bled down system, you never needed to vacuum it at all. But you do have the peace of mind knowing that there isn't a vacuum leak, that's worth a little bit. But we pretty much knew that already and it cost you several cans of freon and half a day?

To do this one right at this point, you'll need to flush the entire system to get the excess oil out, vacuum down again, charge only with 4 total ounces of 150 viscosity Ester or PAG oil and begin jotting down evaporator outlet air temp and low side pressures at the empty 2nd, 3rd, 4th and part of the 5th can. A tech that knows what he is doing would go ahead and add the entire contents of the 5th can looking for the proper low side pressure / evaporator temps to show up, if he didn't see those before that point - when they don't EVER happen and it's overfull by specifications -- there's your sign that there IS something VERY wrong with the system and you then need an expansion valve replaced after verification that the dryer, and/or other system components/supply lines do not have restricted flow. He would have done it only wasting three cans instead of your 7, 8 - how many when you finally get done? When this approach fails and we still have no joy, then the call is made for a new, pricy compressor, but some compressors are actually so cheap one can throw this new part at it without too many regrets. One way to look at it is how much money do you pay yourself on this farm? $150 for a new compressor can be worth one single day if one can be had for that price range.

Flushing the system above means removing the compressor and draining it of every drop of oil possible, this is not an easy task in itself and if you used the wrong type of oil, it too should be flushed separate from the tractor. Flushing the system is done without the compressor attached to the lines normally. A new compressor solves this time consuming problem nicely but it can be a pricy option.

I do not think your compressor is a little weak, I think it's quite rare for a compressor to break one or more one way valves in order to become weak - it does happen, I've never seen it myself. It could be that it has an overcharge of oil in it to begin with - 4 ounces is a very low amount. Wrong type of oil compounds the issue drastically. Did you get the tractor brand new or was it purchased with low hours already on it as I'm wondering what the other guy might have done if that wasn't you. One can listen to a compressor turned over slowly on the bench to hear if all cylinders are contributing, they can also be partially disassembled to visually check the thin metal reed valves to confirm that they all are there intact and working fine. You may need gaskets to put it back together properly though.