Hi guys.
Firstly this is on a 1991 Toyota Supra 2.5TT JZA70 MkIII with R12 air con. This might be better answered by someone who knows about air con etc....
My air con stopped working, had it recharged, and it barely worked after the recharge. I got it diagnosed and they found no gas in the system.
I managed to come across all of the equipment necessary to recharge with R134a myself so I thought I would go along this route instead of paying a garage to sort it for me.
I found the condensor was corroded and had a leak so replaced that. I also replaced the receiver drier with an R134 compatible unit. I removed all pipework and replaced O-rings and cleaned internally. I also removed the compressor and fitted all new seals, and new reed valves at the same time as cleaning all existing oil.
So everything apart from the evaporator and expansion valve has been removed and pretty much overhauled.
Put the whole system back together, dropped down to a vacuum for a couple of hours, then charged with the right amount of Oil and R134 refrigerant.
OK, the system now blows cold air, however I still dont think it is up to spec.
When I turn the car on in the morning from cold, and set the blowers to max cold I get 4-5 degrees at the vents for about 20 seconds. This then creeps up to 9-13 degrees and hovers around there for the rest of the trip.
If I plotted a graph of temperature against time I would have a smooth wave, going up and down between 9 and 13.
At the same time, if I put the gauges on the air con, I get 30-40psi low side, 130-150 psi high side, and the pressure goes up and down at the same rate as the temperature.
At 9 degrees the gauges are on 30/150, and as it creeps up to 13 the gauges tend towards 40/130.
Once the car is warmed up the temperature fluctuations also seem to in time with the radiator fan coming on and off for some reason.
I had wondered that I may be experiencing a partially blocked expansion valve, perhaps due to freezing, as initially I get good cooling, then as it goes between 9 and 13 it is freezing, and then defrosting and then freezing etc...... I did leave it pulled down to quite a heavy vacuum for a long time, and would have though after a few weeks of running, any remaining water would have been pulled out by the drier.
If I feel the low pressure pipe coming back from the expansion valve to the compressor it feels slightly cold, but not so much it is sweating. The high pressure side is definately warm.
Does any of this ring any bells with anyone. Can expansion valves deteriorate so much they make freezing more prone. I cant imagine it is a blockage due to debris as it is too periodic for the blockage to be something floating around, but then again I'm not sure.
Perhaps its something electrical. Maybe the coolant sensor is getting bad, and this is throttling back the air con somehow, as it seems to be when my radiator fan comes on, the heat starts to creep up, then the fan goes off and the system starts to cool. Or then again, this could be normal behaviour as you would expect the air con to work less when blowing hot radiator air through the condensor, however I see exactly the same behaviour when I am on the road and cold outside air is running through the condenser (which is before the radiator).
On the radiator fan side of things, it is only since I removed the condensor and replaced this, that my radiator fan comes on at all. As far as I can remember, it has never come on, and the temp gauge used to suggest that everything stayed normal without the fan, even when stood still for a long time. Perhaps I have distrubed something, or even fixed a problem I didnt know I had with the fan, or sensor.
So, any clues, anything to try before I get the evaporator out and replace the expansion valve.
Thanks for your time.
Graham Wharton