AC pressure readings and problem with dealer.

Jonas302 said:

So have you had the machine in the summer before Had it worked well and then not as well ?

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I got the machine this spring. From the beginning I thought that the AC seemed kind of weak. But it became obvious now that it's hot out. It's been in the 90's and humid lately and when I use the machine I try to use it early in the morning because it starts getting pretty uncomfortable as the day goes on. Then I jump into the 25 years old beat up backhoe and use that for the rest of the day, lol.

Birken Vogt said:

The only official way to check charge is to recover and weigh back in charge. If you have a thermocouple you can insulate and attach to the liquid leaving the condenser, you can check subcooling and that is also a valid way to do it but more art and judgement required than the weight method. Otherwise you are somewhat shooting in the dark but it can be done that way too.

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Sounds beyond my limited capabilities. I do have a vacuum, a tank of 134a and a scale but according to the dealer it has the right amount of freon in it. And when I did add more refrigerant to it, it didn't seem to change the pressure readings.

You are handicapped with this being under warranty.

I didn't notice it was under warranty. Maybe a call to corporate that you have taken it to the dealer and they don't know how to fix it.

Maybe you can sit in another one with your temp gauge or even someone on here can take a reading then go hard up the ladder at the dealer get your salesman involved too

A/C can be more art than science at times and it can be extremely frustrating to troubleshoot. Oftentimes manufacturer service info can be crappy as well.

it takes time and experience and a lot of times it can be hard to get that experience. The dealer probably doesn’t have someone with that experience.

if this is an orfice tube system make sure the tube is installed and properly oriented. I’ve had one machine brought to me that stumped me for a while until I checked for the orifice tube in place and it was missing, installed one and she worked perfect. It would be extremely conceivable to be missing one from the factory

I haven’t used an ac scale for years. I have better luck going by pressure readings it seems.

After a 30 min or so vacuum I add Freon to the high side until my gauges read around 60 or so psi and at the point I fire the system up. If it’s 90 or above I will add Freon until the high side hits around 250. You want your working pressure around there. Once you get to about 220 let it run for a while and see where the system levels out at. Your low side should be around 30 or so psi if if the system is working properly. The key is to add Freon slowly. You can dump to much in and overload the condenser which will cause your pressure to spike way to high.

if you hit 150 to 200 on the high side and your low side just keeps climbing while not getting cold air you have a weak compressor most times.

On some machines the condenser and condenser fans are strong enough to keep the high side low but you’ll have frigid air at that point.

I know the scale is the proper way but as stated I’ve found it’s way more of an art then a science.

170 seems way low on the high side. If you don’t want to vacuum the system and start over I would add Freon until the pressures start to come up. Bring your high side up to about 200-250 and see how it does. If it doesn’t change anything evacuate the system, add the recommended amount back in and keep fighting the dealer.

Jonas302 said:

Maybe you can sit in another one with your temp gauge or even someone on here can take a reading then go hard up the ladder at the dealer get your salesman involved too

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That's a good idea. I think I'll post in the compact excavators forum and see if someone will check their machine. The dealer told me that he checked another new one they have in their yard and it was blowing at about 54 degrees in 90+ degree temperature. But he also said at the same time mine was at 56. It might do that after running a few minutes but after the machine is warmed up it's around 60.

Knepptune said:

I haven’t used an ac scale for years. I have better luck going by pressure readings it seems.

After a 30 min or so vacuum I add Freon to the high side until my gauges read around 60 or so psi and at the point I fire the system up. If it’s 90 or above I will add Freon until the high side hits around 250. You want your working pressure around there. Once you get to about 220 let it run for a while and see where the system levels out at. Your low side should be around 30 or so psi if if the system is working properly. The key is to add Freon slowly. You can dump to much in and overload the condenser which will cause your pressure to spike way to high.

if you hit 150 to 200 on the high side and your low side just keeps climbing while not getting cold air you have a weak compressor most times.

On some machines the condenser and condenser fans are strong enough to keep the high side low but you’ll have frigid air at that point.

I know the scale is the proper way but as stated I’ve found it’s way more of an art then a science.

170 seems way low on the high side. If you don’t want to vacuum the system and start over I would add Freon until the pressures start to come up. Bring your high side up to about 200-250 and see how it does. If it doesn’t change anything evacuate the system, add the recommended amount back in and keep fighting the dealer.

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Before I had the machine worked on the first time, I added about 8 oz. of freon and it did not change the temperature or any of the pressures on the high or low side.

JD955SC said:

A/C can be more art than science at times and it can be extremely frustrating to troubleshoot. Oftentimes manufacturer service info can be crappy as well.

it takes time and experience and a lot of times it can be hard to get that experience. The dealer probably doesn’t have someone with that experience.

if this is an orfice tube system make sure the tube is installed and properly oriented. I’ve had one machine brought to me that stumped me for a while until I checked for the orifice tube in place and it was missing, installed one and she worked perfect. It would be extremely conceivable to be missing one from the factory

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I don't see an orifice tube being shown in the service manual. It does have an expansion valve, could that be causing the problem?

Doug580l said:

I don't see an orifice tube being shown in the service manual. It does have an expansion valve, could that be causing the problem?

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your expansion valve is your metering device (the same function an orifice tube provides)

Of course If it has failed it could very well not cool correctly.

Knepptune said:

I haven’t used an ac scale for years. I have better luck going by pressure readings it seems.

After a 30 min or so vacuum I add Freon to the high side until my gauges read around 60 or so psi and at the point I fire the system up. If it’s 90 or above I will add Freon until the high side hits around 250.

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I was always taught to add refrigerant to the low side and let the compressor pull it in from the suction side. My personal thoughts would be to get the heater hoses shut off as that will add a few degrees to the vent temp. Next if you can’t get pressures up by adding in refrigerant you’ve either got a failing compressor or a stuck expansion valve. I usually test the expansion valve by pulling a vacuum as low as you can and then closing the valves on your manifold. If it doesn’t hold vacuum then your expansion valve is malfunctioning and should be replaced. Honestly if I were the stealership tech I’d have replaced the compressor, dryer, and expansion valve or orifice tube and used the 23 ounces as a starting point.

On a running system I always add to the low side but if the system is vacuumed out I’m turning the can upside down and dumping liquid into the high side. I’m to impatient to bring it from zero on the low side.

To vac the system you should open both the high and low valves on your gauges. Vac for an hour minimum then close off your valves. Your vac reading should maintain for a minimum of 45 minutes to ensure there isn't. any leaks. Purge your freon line then open the low valve only (the high valve shouldn't be touched throughout the rest of the filling process). When doing the initial fill with the engine off (that's the way I do it) , notice the gauge readings once it levels off.........the high and low readings should be exact or close which indicates a proper set for the expansion valve........in other words it should be functioning. Start the engine, a/c on, high blower speed with recirc on if you have that. 1500 rpm is good for filling. Check the ambient temp according to a chart, then crack open your low valve and let the system take freon in 50 psi increments (again, this is the way I do it) waiting a few minutes between 50 psi charges. Watch your vent temp........ideal is 35-45 degrees which in a mini you won't get. Get the high side to the reading on the chart......it should be around 7 times the low reading.....in other words, if the low is 30 psi, the high should be around 210 psi on an average system. Look for a vent temp within the specked range.

This is basic steps; I haven't used a measured load for 30 years...........it's a feel thing for me. There is always a system that just has to be different and out of the normal.

Before you even start this, you really need to pinch off the water flow to your heater core FIRST. The shutoff valves are usually crap and don't seal worth a dam. Even slight flow through the valve to the heater core can make a 10–15-degree difference in your air temp.

I've not seen anybody mention "superheat", nor "subcooling" which can readily determine the efficiency of the coils and interpreted correctly, the overall system operation. "Superheat" measurement will determine the efficiency of the evaporator coil, "Subcooling" does the same for the condenser coil. Both must be clean and both must have adequate airflow across them for proper operation.

VeTech63 has given the best advice I've seen as far as "generic" information, but true superheat and subcooling measurements are universal and have definitive numbers for any mechanical cooling system.

You can see from reading this that there’s a bunch of different ways to go about it and that pressures are more indicative than absolute.

This is the kind of stuff that drives a lot of people absolutely nuts, including me, when working on AC systems.

In the minis I have seen, the condenser is way undersized in my opinion. It's rare I can get to a good vent temp because there just isn't enough temp drop across a small condenser. Since the OP's machine is new and under warranty from what I understand, I'm wondering if the issue is bleed through from the heater core or a lack of airflow through the condenser.

The bad thing is.....by screwing with it under warranty as a consumer, there is a chance the dealer can deny warranty if the owner creates a problem with the a/c system. Right now you're damned if you do, and damned if you don't. You have to pick your poison here.

A quick check on a condenser cooling problem..........spray it with water while your a/c is running............the temp will go down with the high pressure in this scenario if the airflow through the condenser isn't enough.

1693TA said:

I've not seen anybody mention "superheat", nor "subcooling" which can readily determine the efficiency of the coils and interpreted correctly, the overall system operation. "Superheat" measurement will determine the efficiency of the evaporator coil, "Subcooling" does the same for the condenser coil. Both must be clean and both must have adequate airflow across them for proper operation.

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I mentioned subcooling in post #25. That is the way to do it for a TXV system, if the condenser is big enough to actually subcool. If it's inadequate, you can end up dumping more and more refrigerant until the high side gets too high and the compressor is overworked. But high side does not seem too high on this system, so my guess is that it needs more, but that is only a guess.

You need to brake down and pay a guy that knows his stuff to look at it stop trying to get it fixed for free. Ask around and find some ac guru maybe even a hvac guy. The dealer is hoping you will get tiered and go away.

If it's a warranty issue and the dealer doesn't have techs. experienced enough to fix it, they should be the ones paying to have it taken somewhere that knows what they're doing. No way the owner of a new machine with only 100 hours should have to pay $100/hr.+ to fix what should be a warranty issue.