aircon stops working after about an hour


Old 01-27-10, 03:57 AM
Thread Starter
Join Date: Jan 2010
Location: Australia
Posts: 1
aircon stops working after about an hour

i have a 94 toy hiace super custom import that has dual air con but 1 compressor and has been faultless for 2yrs till now, the front air con is mostly working on cold days for about an hour then it dies off, yet if i turn the back one on its always 100% fine. to get the front working again i need to park up for a couple of hours. if i leave van out in the hot sun and then turn aircon on the front one wont work but back one is still fine.
i have found evaporator and washed it and the drain is not blocked and i dont think it ices up. i have found that there is water draining when working but stops leaking when in faulty state, rear drainage always works, if front air con only is used and is in faulty state i believe the compressor stays on, also i dont see anything in the little gas glass window next to the drier
hope this is enough info and not to confusing
many thanks
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Old 01-27-10, 07:00 AM
Tolyn Ironhand's Avatar
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Join Date: Nov 2007
Location: USA
Posts: 11,889
I'm from the US so things may be different but, sounds like you do not have enough air passing over the evaporator in the front, (the part inside the dash where the fan blows the cabin air through to cool it) and it is freezing up. Check to see if you have a cabin filter or if the air ducts are clogged with something.

If everything is good then you might be getting low on freon which also can cause the evaporator to freeze up. I still suspect the filter though because you said the back is working fine and you said it only has one system.
Old 01-27-10, 09:41 AM
Join Date: Dec 2009
Location: Kingsport, TN
Posts: 217
I have a vehicle that would do the same thing but it did it after about 20 minutes or so. In my case, it was a bad solder connection in the circuit board that controls the thing. Mine was a manual system on an older car so the board was not too elaborate.

On another vehicle I used to have, the system would go to full heat after about 5 minutes. In that case it was a transistor breaking down when it got hot. I found it by spraying refrigerant on the circuit board just as soon as it misbehaved. It would immediately go back to AC for a few minutes until it got hot again. I replaced the transistors.

When your AC quits, is there power still going to the clutch on the compressor?
Old 01-27-10, 11:05 AM
Join Date: Oct 2008
Posts: 1,312
There is a "gizmo" near the evaporator which releases refrigerant pressure. This can freeze up if there is moisture in the A/C refrigerant lines. The solution for this problem is to replace the dryer, evacuate the A/C system, then recharge to factory specifications. This problem can be caused when the A/C refrigerant system is opened for any reason, then the dryer is not replaced and/or the system is not properly evacuated prior to filling with refrigerant. (The dryer MUST be replaced anytime the system is opened.)

A different problem is that the evaporator (cooling coils inside vehicle) are reaching a temperature at or below freezing. Then ice forms on the coils and air can no longer blow through the coils. The symptom of this is very little air coming out the vents. If this is the problem, then you would need to look at the factory service manual and see what causes the flow of refrigerant to stop just before it reaches freezing. Then check that gizmo.

I don't know about your specific vehicle. But on other vehicles there is an electrical temperature sensor. This shuts off the compressor just before the evaporator reaches freezing. On other vehicles there is a pressure switch which shuts off the compressor when the refrigerant is at a certain pressure. (Does same thing.)

But they like to design every car differently! So no telling how your system works? Complete information on how your HVAC system works and troubleshooting instructions would be in a factory service manual set which you can order from your dealer.
Old 02-09-10, 12:38 AM
automd's Avatar
Join Date: Oct 2009
Location: Indiana, USA
Posts: 38
I have had a similar problem and the root cause was the A/C clutch on the front of the compressor was wearing out. check yours, could be the problem.
Old 02-10-10, 04:56 AM
Join Date: Feb 2010
Posts: 2
In these days we have automatic hi-ace in our country. I have not yet seen them but I have heard about them.

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