1736 Premium Cab - ac working intermittently

[zdman]

The AC is not working properly in the cab. Seems to run and blow cold air for a while, but then the air coming out is only a little cooler than outside air temp. Seems to do the same whether in fresh air or recirculate mode. Any ideas?

 

[jeepcj7]

Could be evaporator freezing up.

 

[Doug62]

I've noticed my 1835M not cooling as well after I've used it heavily for a while. I think under heavy loads the compressor might be shutting off like it does on a car when you accelerate hard.

 

[zdman]

I've noticed my 1835M not cooling as well after I've used it heavily for a while. I think under heavy loads the compressor might be shutting off like it does on a car when you accelerate hard.

I was thinking the same thing, but was doing it the other day and it did it again and there was no load on the tractor - using to set a few brace posts.

 

[lpakiz]

I’m just guessing here, but could you watch the drain hose, from under the evaporator, for water drops? Mine (and most vehicles with AC) drip pretty heavily in muggy weather.
If it drips good at first, then stops dripping, it might be icing/freezing up.

Or when you shut down, put a catch-can under that drain hose. If it gets some water in it after a 1/2 hour of not operating, that could be ice blocking the evaporator coil, then melting and running out.

A plugged cabin air filter could be the culprit, and on trucks, we used to run into a faulty blend/mix door or actuator not allowing enough air thru the evap to keep up with the cold you are making.

 

[zdman]

I did check the cabin filter (is on outside of the cab under roof lip) and it was fine. I did watch and am not seeing any water coming out or the drip hose. Normally there is a lot coming out after ac has been running. I need to find out where the connector is to measure and add Freon.

 

[lpakiz]

Unless you’re sure it’s low, adding Freon doesn’t mean more or colder air. If you have good air flow from the ducts, check the compressor to see if the clutch is turning the center hub. The clutch is controlled by several pressure switches in series. If the compressor is indeed running, the bigger of the 2 pipes going into the compressor (suction pressure) should be pretty cold, and the small one should be quite a bit warmer.
If I suspected a sensor, I would hot wire the clutch (careful here, hope you know what you’re doing) and see if cold air was produced. If this resulted in adequate cold air, there’s nothing wrong with the mechanics of the system, including freon level, belt tension, plugged evap or condenser, etc.
The problem is in the switches controlling the clutch.
This might be the time to call for reinforcements…….

 

[metalbender]

Airflow through condenser good??? Clean the screens at the front.

 

[jaxs]

PM me if you don't figure it out,I might be able to take a look if you want.

 

[Bavarian]

Just blindly adding freon can result in a costly repair. Spend the money for troubleshooting and not on replacing costly components caused by guesswork.