JD 3720 Air Conditioning line pressures?

[jonyyuma]

Guys Thanks for letting me hitch-hike in here..I see that i am doing okay with my Toyota..But our newer car will really chill you and it is 134 charged too? I do have the guages and temp gun, plus a thermometer spike for my dash register..Got to send this to a printer for a hard copy...Now going to do a little more investigation, before opening another can..Amazing how rusty I have gotten in the last five years..Have a great day...Gentlemen..JY.>>

 

[jenkinsph]

Guys Thanks for letting me hitch-hike in here..I see that i am doing okay with my Toyota..But our newer car will really chill you and it is 134 charged too? I do have the guages and temp gun, plus a thermometer spike for my dash register..Got to send this to a printer for a hard copy...Now going to do a little more investigation, before opening another can..Amazing how rusty I have gotten in the last five years..Have a great day...Gentlemen..JY.>>

What you may find on the older car is that the condenser coil is blocked as metioned in the above posts. If you can't drop the temperature of the hot gas running thru the condenser you wont be able to get the heat absorbtion you want thru the evaporator coil. This may sound overly simplistic but still pretty close at any rate.

 

[JDneophyte]

I think I'm close to being an "experienced" John Deere 3720 Air Conditioning trouble shooter (with a lot of help from the dealer). Problem solved.

What did I learn? After finding the high side pressure "kicking" out the compressor at about 350 PSI, I changed the expansion valve (which meant removing the cab roof) and the dryer in front. This didn't help....but put me one step closer to solving the problem......compressor or evaporator coil (up in the cab roof). So, instead of going it alone, I called our local dealer and their air conditioning expert came out to the farm (which was a 100 degree day in Wisconsin). He trouble shot the A/C system for 2 hours and found nothing wrong.....EXCEPT......behind the battery and turbo cooler (which none of us can see or clean)....was COMPLETELY PLUGGED!!!! We took our pressure washer and completely cleaned it out, blew it dry, and fired it up.......47 degrees coming out the vents!!!!

I asked the gentlemen how this could affect the system, he stated "It's a bad design...very little room for ANY inefficiency in the way the system cools down the high side". Which I stated...."It's a farm tractor......aren't these things meant to be loaded with dust and dirt and keep on chugging?".......which he replied..."exactly".

So, removing the battery, taking the two hold down bolts on the turbo cooler out (leaving it attached via the two hoses) and pressure washing.....is the answer in my case. Though, after reading many threads on this topic.......keeping the condenser clean along with the back filter is the key.......it's getting to it that takes time and effort.

 

[JDneophyte]

Ill lay money on that You've got a plugged condenser. If it was a restriction the high side will climb and the low side will drop and even go into a vacuum. I had a fellow call me one time with the same complaint. He swore the condenser was clean, and it did look it. But I took the battery out from in front of it loosened the coil. It was a double row coil and had all kind of trash in the middle you could not see .... do the same with yours. Powerwash that coil. Just make sure the wAter stream goes straight into the fins to keep from bending them.
This all presumes it has been running right before and no one has overcharged it

****!! I wish I had gotten to the forums sooner to read this reply.....this is exactly what was wrong. Thank you.

 

[Dr Dave]

Glad you got it working, R134a systems are very temermental, when it comes to condensor airflow.

Yesterday my son wanted to borrow my guages and 1 can of freon, I said clean the condensor first, he added 1 can, no improvement, bought another can and added it, still not cold. I went to his house and asked did you clean condensor?
After an hour to disasemble and clean the condensor, the driveway was full of debris. Now I have to reclaim and recharge it.

 

[sunnyside360]

So, removing the battery, taking the two hold down bolts on the turbo cooler out (leaving it attached via the two hoses) and pressure washing.....is the answer in my case. Though, after reading many threads on this topic.......keeping the condenser clean along with the back filter is the key.......it's getting to it that takes time and effort.

Glad you got'er back up and running good. Yep, sometimes we learn the hard way -- I did on my 3720. I'm to the point of using compressed air to blow out the radiator and condenser after every use.

 

[shortthrow50]

I found that after mowing, compressed air is not sufficient enough to remove all the tightly packed debris from air conditioner condenser up front. I use the power washer. Is the only way in my experience to completely remove debris. I also found that unless you remove battery, there is stuff there as well you might want to clean.

 

[JDneophyte]

I must of spent 8 hours on the tractor before getting help. I did notice (as I bought it with 1700 hours on it) some one had worked on the A/C before me (the expansion valve socket head cap screw was stripped).....and their was some "A/C tape" in between the hot/cold control cables in a hold down point between the cab and cab roof. It looks like the designers of this system did a great job in how to fit so much in a small space, but didn't have enough room up front to add an adequate condenser (as it should not over heat with basic use). I thought about placing a better filter between the radiator and condenser to catch particulate, but after loading the front of the tractor grill with dandelion seeds....and having the A/C kick out due to overheating.....the only solution would be an alternate location for the condenser (or much bigger condenser).

But ****.....on a 100 degree day with that A/C blowing to the point you have to turn it down......nothing beats it when cutting 5 acres!!

 

[sunnyside360]

But ****.....on a 100 degree day with that A/C blowing to the point you have to turn it down......nothing beats it when cutting 5 acres!!

Your A/C unit is working very well and you must be very happy. My 3720 A/C has been anemic since it was new in 2007. It was really weak when new before the roof seal was replaced. Cab tractors are useless w/o the A/C working in this hot weather --- been there and done that.

 

[JDneophyte]

Your A/C unit is working very well and you must be very happy. My 3720 A/C has been anemic since it was new in 2007. It was really weak when new before the roof seal was replaced. Cab tractors are useless w/o the A/C working in this hot weather --- been there and done that.

I concur. Did you get your cab cool eventually?