A/C leaks out, fans don't come on with A/C Sherlock solves case - Taurus Car Club of America : Ford Taurus Forum
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post #1 of 2 (permalink) Old 04-17-2019, 07:27 PM Thread Starter
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A/C leaks out, fans don't come on with A/C Sherlock solves case

Been trying to fix this for a year with no luck.

'07 Taurus. No frills fleet car.

A full charge of R134a would leak out in about 2 weeks. Engine cooling fans wouldn't come on when A/C selected on. I went all over it with a sniffer and couldn't get anything more than a background reading and once in a long while a couple of beeps around the compressor but nothing after that.
When I hooked up my gauges I noticed the fans came on high only, when the engine got good and hot.
I sprung for the factory wiring diagram, which is a little more detailed that the Chilton book.

I took all the relays in the fan circuit out, there are three of them, and tested them. Tested all the fuses in the circuit and I found the low fan signal wasn't ever getting out of the PCM. I was about to spring for a new PCM when I decided to have a look at the dual pressure switch which sends the A/C on signal to the PCM. Fortunately it's located on the top of the block that connects the hoses to the compressor, right on the side where you can reach it easily. (maybe the only thing on the taurus that's easy to get to.) When I took the connector off, it was full of oil. It shouldn't be full of oil. That meant it was probably leaking internally.

So I replaced it. Now the fans work and hopefully the refrigerant will last a good long time.

Now, from a design standpoint, wouldn't it have been easier to have sent the switch signal directly to the low fan relay instead of running it through the PCM and two relay boxes fed by four different fuses? Good old Ford.
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post #2 of 2 (permalink) Old 04-17-2019, 08:42 PM
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Does the switch supply the high low signal or just the low fan signal when AC is on.
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