Thread: weird aircon problem

did the aircon place actually put a guage on it to see what pressure was in the system......?

ditto.

I'd be running gauges back to the cab and taking it for a run.
4*C air off is pretty low, you are running a coil temp well below zero to get that figure.
I'd not like to guess at anything until you knew what pressures you were running.

I have to get out to an excavator that runs for two hours then bundy's off. The operator shuts down the entire machine, then re-starts and the damn a/c goes for another 2hrs, etc.

I am not an aircon specialist but what about
TX valve partially blocked
Receiver dryer partially blocked
High pressure switch cutting off compressor clutch.(faulty?)
Low pressure switch cutting off compressor clutch.(Faulty?)
Does the compressor cycle when the air is warm? If not I suggest it points to the pressure switches.
The other is that the thermostat is not cutting out and the evaporator is freezing, but this usually occurs after a while.
Finally- I think a Disco has a similar setup to a RRC where there is a vacuum operated door which opens when recirc is selected. This may not be opening for a while. This also ties in with the aircon going warm on acceleration. A vacuum leak in the aircon flap motor or the vacuum pipes.
But usually the aircon works but goes to the floor not through the vents.
Regard sPhilip A

Originally Posted by PhilipA

I am not an aircon specialist but what about
TX valve partially blocked
Receiver dryer partially blocked
High pressure switch cutting off compressor clutch.(faulty?)
Low pressure switch cutting off compressor clutch.(Faulty?)
Does the compressor cycle when the air is warm? If not I suggest it points to the pressure switches.
The other is that the thermostat is not cutting out and the evaporator is freezing, but this usually occurs after a while.
Finally- I think a Disco has a similar setup to a RRC where there is a vacuum operated door which opens when recirc is selected. This may not be opening for a while. This also ties in with the aircon going warm on acceleration. A vacuum leak in the aircon flap motor or the vacuum pipes.
But usually the aircon works but goes to the floor not through the vents.
Regard sPhilip A

again, pressures and temperatures tell all.

Originally Posted by DEFENDERZOOK

did the aircon place actually put a guage on it to see what pressure was in the system......?

Yep the hooked up the hoses and checked pressure and it was ok, they added a couple of extra squirts in also.

Originally Posted by PhilipA

I am not an aircon specialist but what about
TX valve partially blocked
Receiver dryer partially blocked
High pressure switch cutting off compressor clutch.(faulty?)
Low pressure switch cutting off compressor clutch.(Faulty?)
Does the compressor cycle when the air is warm? If not I suggest it points to the pressure switches.
The other is that the thermostat is not cutting out and the evaporator is freezing, but this usually occurs after a while.
Finally- I think a Disco has a similar setup to a RRC where there is a vacuum operated door which opens when recirc is selected. This may not be opening for a while. This also ties in with the aircon going warm on acceleration. A vacuum leak in the aircon flap motor or the vacuum pipes.
But usually the aircon works but goes to the floor not through the vents.
Regard sPhilip A

no Phillip the compressor does not cycle when it's blowing warm air.
I had a problem a long while ago the same as now and I fixed it by replacing the compressor clutch relay. It was not holding due to the contacts in the relay letting go. A new relay fixed it.
So naturally We went down the same track this time and replaced the relay and it started working ok, then put the old one back in and it stopped. new relay in and it ran. But then I had this problem of it cutting out on acceleration
Will have to check out the circuits over the weekend.

Originally Posted by Rovernaut

Yep the hooked up the hoses and checked pressure and it was ok, they added a couple of extra squirts in also.

pressures vary quite a bit with load and compressor speed. I'd be looking at pressures when on the road and see if it tallies with the symptom. If it does, then you can start to fault find.

What about wiring in an independently manually switchable 12v feed to the clutch that you can drive with, & see if it operates normally?

If it does, then the problem is elsewhere but at least you will know.

The only thing against this, is you won't have the protection of the HP or LP safety cutout as it won't be dropping the clutch out.


I suppose at those supposed temps (if they are accurate) it could also be moisture restriction at the TEV & it's cycling out on LP.