Branson 6530C still having AC issues

[dclt736]

Afternoon TBN family
Last year i posted about AC issues with this tractor. Based on the work i had done last year, we thought the problem to be a leak within the AC compressor unit, due to the leaking of coolant and oil from the rear of it. So we had a new compressor and air dryer installed a week ago.
At first the system was recharged with 2.78 lbs of 134a based on the data in the owners manual.
The AC worked for about 45 minutes before the system was blowing warn air.
And the compressor was short cycling, in that it would turn on for less then a second, and then try again 4 to 5 seconds later.
Tech felt the the charge was not enough.
Working with my local dealer, they contacted Branson US and came back that the system should be charged with 3.5 lbs.
So we reloaded it to that level and i took the tractor out for bush hogging.
And within 30 minutes of that, unit was blowing warm air again.
And no the condenser is not plugged with dirt etc, that was fully checked and i know about this being an important check on AC.
Tech still feels that the system is just not charge enough, but as this is the second time they have filled it i am second guessing.
For me, if you can get cold air for 10 to 15 minutes with both 2.78 and 3.5 lbs of gas, but then once the system starts to blow warm, no amount of letting the tractor sit not running for a few days, will give you any sort of cold air on the next run.
That seems to show either the charge is loss with a leak, or some other fault is at play.
Both time the system was filled, it had a full pump down, vacuum, and refill.
And they said that the pump down between the 2.78 fill and 3.5 fill showed no real loss of gas, which if no loss of gas, points to some fault that might be corrected from the vacuum work and revert once real pressure in applied by the AC compressor?
Tractor is going back into shop Wed afternoon, so just wondering if anyone has an ideas of what else to look at?
Thanks
Douglas

 

[cbg8670]

Try letting it run. When it quits blowing cold shut it off wait 30 min and start again. If it works after letting set then quits again. It has trash or moisture in system . Plugs up ,quits working then starts after setting

 

[dclt736]

Thanks cbg8670, i have done that, and it only blows warm air, regardless of how long i let it sit, including two full days of non operation, which seems to point to a loss of gas. However the AC tech are saying the amount of gas at pump down is mostly showing to be what was put in, so for me, it is pointing to some other fault in the system.
I will have more information, once they put gauges on it on Wed, which will show the high and low pressures and if the system is acting like it has lost gas.
I think we have a leak, but will know for sure if when they pump down the system and they don't recover 3.5 lbs of gas.
And if they do find i still have all the gas they put into it (3.5 lbs or very close to that), then that points to some other fault that corrects itself when there is no pressure in the system, but then once in operation cause some sort of gas flow problem and thus the lost of proper operation.

 

[Cougsfan]

I would say you have moisture in your system.
Did you pull a good vacuum and let it set for a day with a good vacuum? I had a problem similar to yours where the system would cool for a while then stop cooling. What was happening was that I still had a bit of moisture in the system. Moisture will congregate at the expansion valve where it turns to ice and plugs the expansion valve. This was why it would work for a while then stop. Once I held a good vacuum prior to charging it worked well. Also you probably should replace your dryer if you have one. (My particular tractor has no dryer installed )

 

[R134a]

The guy at the dealer is not a tech. What he is...is clueless. He presses buttons on a machine. What happened to the high/low pressure reading when the system was running ? Whats the charge...2.78 or 3.5 ? They are flipping a coin hoping for the best.

 

[dclt736]

Thanks Cougsfan, and yes my system does have an air dryer can, and they did pull vacuums both times before the refilling, but only for say an hour or so, and then waited to see if the vacuum held for 30 minutes which is why they believe there are no leaks as the vacuum held.
But if the system has a small amount of mositure, would the system not blow cold air a a little while if it sat for a few days in warm weather and not operated?
Ie, the water would turn back into vapour, and the expansion value then work for a short time?
What i see is that the system does not work again after it starts to blow warm air.
So far, what i am seeing or told is that the system is not charged correctly, which i just cannot wrap my head around.
However, all i know is what i have learned from watch different youtube AC tech video's and from the guy working on the AC.

 

[dclt736]

The guy at the dealer is not a tech. What he is...is clueless. He presses buttons on a machine. What happened to the high/low pressure reading when the system was running ? Whats the charge...2.78 or 3.5 ? They are flipping a coin hoping for the best.

My guy is a long time Ford mechanic running his own shop now and highly respected in the area. That being said, he is a auto mechanic. He has modern equipment as well. The refills has been done twice, and accurately. He filled it to 2.78 lbs as pre the Branson owners manual. System work for a short time, acted like it was short of gas. Branson US then told us it should be 3.5 lbs not 2.78, so we pumped the system down, did a new vacuum and put in 3.5 lbs. System worked fine for them which was letting the tractor run for about 20 minutes. It then fail for me about an hour of operation later. Now his work is not 100 percent AC, so maybe he is missing a fault that only a full time AC tractor guy would find, but show me a shop that has a full time AC tech on farm tractors, they are hard to come by.
I will say that you can do a lot of debugging with the pressure readings if you spend the time to monitor them, say over an hour or so, but to be fair, as with all repairs, sometimes we look for the easy fixes. So on Wed, i will be onsite and will make a point of see what the gauges do and will ask questions based on that. I do think that i have a problem that is not based on the amount of fluid put into the system, which on the face of it, more then one source has suggested the system just isn't charged to the correct level. I think that i could have a expansion value that is faulty in someway, but i am no AC expert. I am looking forward to seeing what the gauges show on Wed.

 

[5030]

So, you made sure the condenser was clean but did you ever bother to clean the evaporator? Don't know where it is but I assume it's under the roof. I clean the ones on my Kubota's every spring and they are usually dirty. I'd also put a full port WOG shutoff valve in the heated coolant line to the cab heat exchanger. I've yet to see a heater control valve that didn't pass a bit of hot coolant even though it's shut off.

Short cycling is usually a symptom of a iced evaporator. They ice up because they are filthy and cannot pass adequate air. I good telltale sign of a filthy evaporator is the air coming thought the vents has a damp smell.

 

[dclt736]

Thanks 5030, and very good comment. Last year i did a full inspection of the evaporator core, which is not a easy task, will post photos tonight as based on your comments i will do it again. I removed the cab lid last night so that we could check those fitting for leaks on Wed, but the evaporator is encased in a plastic housing holding the fans and heating core and it does take a fair amount of delicate work to separate the housing. Last year when we did the AC work, the inspection was done, and i can guess i most likely was the first person to see it since build. It was a little dirty then, but in no way was it plugged. I owned the tractor for over 8 years and had not AC issues up until last summer, and if the core was only a little dirty then, i do believe i will not find any real issue when i open it up. Photos to follow tomorrow. Also when the system was working after the refills, there was no smells that i picked up on, either damp, musty, of any sort of chemical smell say for the gas leaking. I am normally pretty good at picking up on that sort of thing, as well as changes in operating sounds. But all good advice coming from the chat so far.

 

[Tntcwg3]

I'm not familiar with the cab tractor systems, do they also have a heat provision? I've ran into automotive systems where the heater control valves were malfunctioning and leaking by, or sometime an airflow damper door was stuck open. In either case, the AC system simply cannot overcome the additional heat. Often time we would install a manual shutoff valve inline to the heater core to resolve the issue.