Rear A/C valve help!

Ok so I had pretty much my ENTIRE a/c system components replaced in 2012 (compressor, condenser, drier, radiator, expansion valves, Evap cores thoroughly cleaned). The a/c system was recharged with r-134 and blew ice cold for months. Then after the summer was over it started blowing warm air and the rear wasn't working. In 2013, found out that the magnet valve (the one part i didn't replace because i didn't know about it at the time) was leaking but when it was cold in the front, the rear was still warm. Put it on ramps at a friends house and saw the neon green fluid around the magnet valve's connections. We checked the voltage to the valve thinking pressure was causing it to leak and it's getting 9v from the van but wouldn't open. We then hooked it straight up to the 12v battery and instantly it popped open and had cold air in the rear so that was solved. Replaced o rings with the correct toyota ones and they had more grab when installing, whereas the old o rings (which I thought were new when they installed all the components) barely gripped the inside of the valve. That may be one reason for the leak but the real question is that because the area around the valve and wires going into the valve was rusted, would this cause the magnet not to open with 9v? How many volts should it take to open the valve? Thinking of just buying a new one due to my gut feeling that the rust is causing the valve to stay closed, 9v not enough to break past the rust. Lemme know what you guys think. Thanks in advance.

Where are you getting the 9V from? If you're using a 9V battery for testing, it may be too big of a load for it (too many amps). Always best to test with 12v anyhow, because in reality, when the engine is running, the system is around 14V anyhow. Tim

The 9v is coming from the thick wiring harness under the driver door that, i believe, goes to the computer. On that harness, it has a 2 wires with a female connector sprouting from it that connects to the male end for the rusted rear a/c mag valve.

I'm not aware of any circuits that run on 9V so I'm guessing there's a problem with the supply circuit. Could be a bad connection or a failing relay??? The newest service manual I have is 93, and they made a lot of changes in 94. Perhaps somebody with knowledge on the newer Previas will chime in. Good luck. Tim

just replace the valve, they do go bad over time and leak... mine leaked and it wasn't the o'rings

Just ordered the new valve. Found a brand new oem without box on ebay for $45 but surprise surprise they think they sold the last one, couldn't find it and refunded my money. So had to spend $235 at mid atlantic toyota parts. If this doesnt open with the 9v, Im going to hook it up to a 12v switch. Fingers crossed. Thanks for all the help guys!

There are no 9v circuits in a previa. timsrv is right on the head. If you are only getting 9v at the plug, then your relay could be going bad or since you metioned excessive corrosion, the wires to the connector or connector itself could be corroded also inside the rubber coating. This causes higher resistance in the wire, heat, and loss of proper power delivery.