AC works for about 30 minutes and then starts to fade(blow warmer) on Jd 3720

[candersen10]

I have a John Deere 3720 with AC. When I use the machine, the AC works for about 30 minutes and then starts to fade(blow warmer). Any ideas what this problem might be?

I've cleaned the AC filter and checked to make sure the compressor spins freely. Does it sound like the system just needs to be recharged? If so, what does that entail and can I do it myself?

Thanks so much

[blueriver]

Every thing is probably clogged with dirt, dust and junk ... use air or water and flush out the a/c coils and the radiator ... flush it real well.. try that first.

[candersen10]

I don't think clogging is the problem.

I regularly blow out:
(1) Radiator
(2) Engine Air Filter
(3) AC Air Filter
(4) AC Coils (which sit right behind the filter)

I should have posted this in more detail in my earlier post. I don't think dirty components are the problem. I don't know enough about AC systems to identify other common problems with them besides dirty components.

[jenkinsph]

As was found in a prior thread a few weeks ago you should remove the battery and clean behind it too. Don't underestimate how important it is to keep the front condenser coil very clean.

[snw]

Assuming that nothing is leaking refrigerant, first check to make sure you have good airflow over the condenser, usually mounted ahead of the radiator. Culprits here are worn electric fan, worn out fan clutch on engine driven fan. The output of the condenser (liquid refrigerant at high pressure, with heat removed by the condenser fins) goes to the evaporator inside cab. To enter the evaporator, it must pass through a very small hole in the form of either a fixed orifice tube or an expansion valve. Passing through, the refrigerant changes from a liquid to a gas (literally "boiling" inside the evaporator) and becomes cold. On the other side of the evaporator is a line at low pressure, that goes to the compressor inlet. (The outlet goes to the top of the condenser.) This line should be colder that the other one, which should be at least warm if not hot to the touch. The closer to the evaporator (cab) the colder it will be.
If it's not cold, or only cool, you are probably low on refrigerant. The cans you can get at any retailer will work, just don't, under any circumstances use one that has any kind of "leak stop." It doesn't work and can cause all sorts of grief, including having a technician refuse to work on it.

[murphy1244]

If your low on refrigerant you have a leak and need to go to your dealer or a AC repair shop as the charge is weighed in.

[Just Bill]

If you don't know what to do, have someone that knows take a look at it.
If you do the recharge wrong you could either damage the system or get hurt.

[Dr Dave]

As said before remove battery and any covers to get access to radiator and condensor, wash the heck out of it.
As the engine heats up, radiator and condensor will heat up, hot in 30 min. Also cab filters or dirty evaporator in cab can cause core to ice up. After cleaning everything, if still acting up, take it to a pro.

[dstig1]

With age and extended use, the clutch on the compressor can wear and the clutch gap gets large. Then when it heats up a bit, the coil cannot pull it in so it no longer engages. The clutch should have one or more shims behind it for spacing the gap. If the gap is out of spec, then pull a shim out to get it back in spec and you should be good for a good long time, if that is the issue. Can't say for sure what the gap is on these, but on most Fords I've had is is about 0.025-0.030" gap. Probably a decent starting point.

There is a way to test this first, in addition to measuring the gap. When the AC should be on but is not (set on max and a hot day), take a broom handle or a long screwdriver handle. First check to see if the clutch is turning or not. If not, then tap it *carefully* with the broom handle and see if it engages. If so, you probably found your problem. If the clutch is turning, then you either have an airflow problem or an internal system problem.

Beyond that, you really need a set of AC gages to diagnose a system. They really aren't that complicated but you do need to know a few things about how they operate. Do NOT just go adding freon without knowing what you are doing.

[shortthrow50]

if im not mistaken, the 3720 has a turbo intercooler in front of the a/c condenser up front. My 3520 does not have an intercooler so i can see very well that it gets debri in the condenser after every mow. Compressed air does not get all the debri out. You will need to use a power washer and have it on a "fan" setting being very careful not to damage the fragile fins in the condenser. Your condenser is probably clogged all the ****. Like mentioned already, the battery needs to be removed to clean it real good.