Help With A/C Question

[trook]

I have a JD 5075E cab, and I'm having trouble diagnosing an a/c problem. When the outside temperature is mild, say 70 degrees, the air temperature coming out of the a/c vents is 45 degrees and the cab cools very well. However, as the outside air temperature increases, so does the temperature of the air coming out of the vents. I realize that tractors have a lot of glass and may be more difficult to cool compared to a car, but let me give you an example:

Over the weekend, the cab was very comfortable in the morning. However, the air coming out of the vents seemed to slowly get warmer as the outside temperature began to increase. Then, when the outside temperature reached 91, the temperature coming out of the vents increased to 80. It was uncomfortable in the cab. The only reason I wasn't sweating was because of the pure volume of air hitting me. You shouldn't sweat inside a cab! It felt similar to being in a 100 degree room with a fan blowing on you. After a rain shower came through, the outside temp dropped to 82, and the temp coming out of the vents dropped to 70. The cab was comfortable again.

Please tell me this is not normal. Deere checked my a/c and freon a couple month ago and everything seemed to be working fine. However, the outside temperature was mild at the time. I hate to think how the a/c would work if the outside temp approached 100 degrees as it normally does this time of the year. I understand that the a/c may have a hard time keeping the cab cold if the outside temps are very high, but 91 degrees doesn't seem overly high to me. A comfortable cab during high outside temps is one of the primary reasons to have a cab.

 

[beenthere]

Agree with your conclusion. Not good for comfort.
A couple things come to mind, that would be the effectiveness of the evaporator and the condenser.
Possible to get them as clean as they can be, with no dust, dirt, debris plugging them up?
Likely there is a certain limit to the capacity to cool incoming air to the evaporator by a certain amount.
Taking your example: Incoming at 82 and out at 70 is a drop of 12 deg. Incoming air at 91 and out at 80 is a drop of 11 deg. Nearly the same difference. So maybe it is just the limits of the design.

Maybe re-routing the cooler air from the cab back through the evaporator would help get a cooler temp, although sometimes that is at the expense of the relative humidity increasing and somewhat uncomfortable.

A dilema...

 

[jenkinsph]

Can't emphasize enough that the cabin filter, evaporator coil behind the filter, and condenser coil in front of the radiator all need to be very clean. I recommend you look closely at the evaporator coil to see if it is dirty, usually caused by a cabin filter that has holes allowing dirt to pass through it. I keep the evaporator coil cleaner on hand for my tractors and it is available at most hvac suppliers as well as some auto parts stores.

If the above doesn't fix the problem I suggest you have a good a/c service man check it out. You should see air duct outlet temperatures approximately 30 degrees F below the ambient or outside air. Make sure the heater knob is turned to the minimum setting and feel the heater hoses at the bottom of the cab to make sure that the water isn't circulating through them.

Heat gain through the glass could be reduced by tinting the windows, to get an idea how much difference this makes park in the shade for 20 minutes in the heat of the day and take readings.

 

[Tx Jim]

Can't emphasize enough that the cabin filter, evaporator coil behind the filter, and condenser coil in front of the radiator all need to be very clean. I recommend you look closely at the evaporator coil to see if it is dirty, usually caused by a cabin filter that has holes allowing dirt to pass through it.

I totally agree. Farm equipment AC's operate in a lot dustier environments than auto's & pickups. If amount of coolant in AC system is correct & orifice is not plugged then lack of air flow across the AC components is the problem

 

[Zebrafive]

I can't say any better than jenkinsph or Tx Jim about keeping the system clean for the best heat transfer.

There are charts that tell normal suction side pressure vs ambient temp, if you have the correct setup to check.

 

[JD3520Turbo]

Is your tractor new? If it is, then there is more going on than just a plugged filter. Is the compressor kicking on and off.? How you can tell this is to let it idle at about 1000 rpm and turn your a/c switch on. Do this while watching the tach and see if it jumps a little downward. If it does then the compressor is kicking on. Let it sit there and run for 15 minutes or so, and if you here the engine changing pitch and or the tach jumping every so often, then your compressor is kicking on and off. You can also raise the hood and watch the clutch on the compressor and see if it kicks in and out. If it does, then that is the first step to making your a/c better. If it is doing that, then you are probably low of freon. The second thing was stated earlier, make sure your heat control is to minimum.
I have had several issues with the a/c on this tractor, and most of them stem from leaking freon. That is why I wrote the above. The other that the dealer finally found, was that the temperature blend door in the cab was not closing all the way and it was getting heat from the heater core competing with the a/c. That helped it a great deal. You want to shoot for a 40 degree vent temp. That is the magic number. It you can achieve that, you should be comfortable in the hottest conditions. When they fixed the leaking freon the first time (didin't actually fix it) they told me that it was blowing 48 degree air, and I told them to keep it until they got it to 40 which they did. It still leaks freon very slowly.

I just used my tractor this past weekend for 8 hours mowing CRP with an HX15 mower in some of the heaviest clover and grass that I have ever mowed. That 15 foot cutter was all my tractor wanted, but it did it. The a/c did a pretty good job early on, but seemed to struggle in the heat of the day.
The first 5083E that I owned had poor a/c performance at full throttle, but would freeze you at idle. Found out that the heater hoses were switched backwards, and when they fixed it, it worked much better. Might want to look into that possibility.
Good luck. There is nothing more frustrating than buying a new tractor and have to have it worked on all the time.

 

[trook]

Thanks JD3520. Yes, the tractor is new. I have about 70 hours on it and have had it for 6 months. I had a Freon leak early on and they fixed that. They also found the reversed heater hoses under the drivers door. I'm not sure, but I believe they already replaced a valve in the roof (accessed on the top rear of the roof) that was possibly letting the hot water mix. They haven't replaced anything inside the cab. As far as I can tell, the compressor is NOT kicking on and off.

What is strange to me is that the vent temp is near that 40 degree mark initially, but warms up as the outside temp warms up. Now, is that due to the actual air temp or a warmed up engine....I don't know. I placed a call to the service dept and someone should check it toward the end of the week.

My condenser is clean, and my filters, while a little dirty, are fine.

 

[Edward. S]

Blow out all the dust under the hood and check the charge on the refrigerant?

 

[Tx Jim]

If I lived where you live I'd install some ""manual heater hose cutoff valves"" similar to the ones I installed on my JD 4255 20 yrs ago.

 

[jenkinsph]

With a tractor this new and in warranty I would let the dealer fix it. That would be my first plan of attack. As Jim mentions a manual valve in the heater hose going to the cab is a good suggestion you can mention to the service person who comes out.