It is not urgent now that it is winter, but the air cond has stopped working on both my TP's. In both cases, the compressors and fans work because you can hear and feel them kick in. However there is no noticeable difference in the air temperature using the blower with or without the air-cond switch on.

Neither used to get very cold but they did give some relief. All of a sudden, both are no use at all. If money wasn't an issue, I'd just get them both regassed but the failure was sudden, not gradual, so I think something else may be wrong. I tried bypassing the thermostat but that made no difference.

What are the two switch thingies in the air cond pipes at the front of the engine bay? I checked their resistance with a multimeter and one is open and the other closed - the same in both cars. Which one is the pressure switch? Also where is the sight glass?

Any ideas what else to check?

Sorry about all the questions but the Haynes manual is not much help.
The manual for 2nd Gens has more info. but they seem to be different.

The sight glass is right down the front behind the passenger side headlight - on top of the dryer usually. If you look through there while the compressor is operating and see only occasional specks of fluid pass by or you just see constant froth, the gas has run out. It's not entirely uncommon for gas to suddenly leak out from airconditioners. In many cases, especially when the system isn't used often, the seals harden and may suddenly crack when they are used again. Officially, you are actually supposed to operate the system for at least 5 minutes once a week during times of non-use to ensure the seals in the compressor are lubricated with oil. The gas leaks out fairly fast when the seals fail, and of course everything will appear to work, but doesn't. According to the wiring schematics for the airconditioner circuit, there is a pressure sensor that will prevent the airconditioner running without gas, or with too much pressure. The fact that the compressor is engaging suggests that the system actually has enough gas, at least enough to not trigger the pressure sensor. This sensor is the device next to the receiver-dryer and is the little black device with wires connected into the top.

The next problem may be with the expansion valve, which is located within the actual evaporator box behind the dash. This valve is controlled by a small temperature sensor which regulates the flow of coolant based on the temperature. If this sensor has failed or if the valve has jammed, no cooling will happen.

Either way, if the compressor is engaging and it is not cooling, you will need to take the cars to a specialist to check the system, as the only tests you can do require special equipment and know-how to perform.

Thanks for your detailed reply, Dave262. I will check out the things you mentioned.

That was interesting.

First off, no wonder I couldn't find the sight glass. There was a circular black sticker over it. I peeled that back and can now see the liquid in there. There seems to be plenty, particularly in the station wagon. When running, there are bubbles but mostly liquid. In the sedan, the proportion of bubbles seems greater but it is not just froth, there is plenty of liquid too.

I read in the 2nd Gen workshop manual that if the compressor is working, you should be able to feel a significant difference in the temperature of the pipes going into and out of the compressor. Well, you can! One side is quite hot and the other side luke warm or cool (but not cold). The difference was more noticeable with my sedan but that may just be because I had it running longer.

Incidentally, if anyone else tries this, keep hands well away from the pulleys and drive belts. You could easily lose fingers. It is probably best to run the engine with air cond on for a while, then stop the engine and check the pipe temperatures immediately after stopping.

The puzzling thing is that the air cond pipes near the front of the engine bay get quite cold on the station wagon but not at all on the sedan. So, that expansion valve seems to be a likely candidate. Is its temperature sensor the air cond. thermostat or is it another one?

if u see bubbles dosen't that mean it needs a re gas?? well that was the impression i was under.

if u see bubbles dosen't that mean it needs a re gas?? well that was the impression i was under.

Yes, that's right but while there's still plenty of liquefied gas, it should at least work, even though not optimally. That is why I think there is another problem as well.

Re-gassing the wagon won't cost too much because I already had it converted to ozone-friendly gas. As far as I can tell, the sedan hasn't been converted yet, so will be much more expensive. I was told that in NSW it is compulsory to convert it if re-gassing. Is that correct?

if u see bubbles dosen't that mean it needs a re gas?? well that was the impression i was under.

It is normal to see a few bubbles, as in the case there are no bubbles at all, the system is actually overfilled.


The puzzling thing is that the air cond pipes near the front of the engine bay get quite cold on the station wagon but not at all on the sedan. So, that expansion valve seems to be a likely candidate. Is its temperature sensor the air cond. thermostat or is it another one?

The return low pressure side of the system will heat up to about 60 degrees, so it will be noticeably warmer than the other side. The main condenser in the engine bay will warm up after it has been running for a bit. There is however no temperature sensors in the engine bay for these pipes, with the only 2 sensors being the thermostat; which turns the compressor on and off, and the the expansion valve sensor; which is non-electronic and controls the flow of gas through the evaporator.

From the sounds of it, the expansion valve may be faulty and you will have to take it to a specialist to get it fixed. I cannot see what else it could be, especially if there appears to be gas flowing through the system. The compressor will turn off if there is a restriction as the pressure will get too high, so the only thing I can see that would cause that situation is a fault with either the expansion valve or the temperature sensor attached to it, forcing it open.

Thanks again, Dave262. I will try to check the temperature sensors and if it is not that, will take them to a specialist.

regards,
Coldamus