A/C always on

[sonic774]

Hello,

One morning of last week, my 2012 Crosstrek 2.0i lineartronic (80000 miles), started with A/C "on", despite the A/C light of the dashboard being "off".
Since then, the compressor stays on all the time. I tried every setting of the heating system, but it never stops the compressor from running. After a while, the A/C pipes are covered in frost and the fan behind the dashboard slows down like it is slowly freezing.
It's summer here and temps are very high.
When I unplug the black wire on top of the compressor, it disengages, and things go back to normal, except of course there is no more A/C.
No CEL, no message on the dashboard, I checked the A/C relay and the fuses : all ok.
The local mechanic says he's not equipped for A/C repair, and the official dealer has given me an appointment for a diagnosis, but not before a full month!

Any idea to diagnose the problem myself? I can do a little mechanics and electronics, have an OBDII scanner with me.
Thank you

 

[sonic774]

I managed to fix the problem myself.

TL;DR : took the car to the dealer who kept it for 2 days to eventually make a wrong diagnosis, that cost me 198.00€. Came back home with my car and a quote amounting to 1400€, kept my brain working on the eletric diagrams, and finally fixed the problem by unplugging/plugging a connector on the ECM.

Ok now for the details. After waiting for a month for the appointment to the official dealership, they took my car and allegedly performed a series of extensive tests of the on-board computers and electronics, and found...nothing wrong. They got in touch with the Subaru HQs of my country, who helped them with trying specific parameters to nail down the issue. Again nothing, but the Subaru HQs said it was probably a faulty climate control console, though they had never seen the problem before.

When I came back to get my car and got these news, I objected that I had already tested the car with the climate control console unplugged, and that the problem was still there. And that I doubted it could be it. At the dealership they told me it was indeed weird, but still, according to them the solution was to replace that temperature console for the price of 1407.36€ (work and all taxes included). And if it wouldn't fix it? No, they couldn't take the parts back because of ... [ usual bullshit here]. Moreover, in that case, next was an ECM (Unit EGI) replacement : I don't have a quote for this one, but it's probably even pricier than the climate console.

Of course I thought it was way overpriced, and started looking at used parts on ebay, and actually found one, for tenth the price. Before I buy it to give it a shot, I started to think it was more an ECM problem and I had to have a look at it. When I realized it was just behind the glove box, with hundreds of wires falling underneath, I remembered the problem happened when we were on holidays with a car packed with stuff, including before the passenger's feet. Actually the wires are barely protected against for example, feet movements and kicks, so I thought it could be a harness or connector problem.

I got my eyes on the electrical diagrams found at http://www.sucross.com/ (thanks guys, you saved my life!) and pinpointed the wire 35 on the B135 connector of the ECM.
Then I removed the glove box, turned on the car, and started shaking the many harnesses found there. It didn't change anything. But then I decided I would try to unplug that B135 connector, even if doing so with the engine started seemed a bit risky (it's 35 wires unplugged at once on the ECM!). Anyway I pulled it out, and immediately plugged it in again, and it did the trick! Problem gone! Probably a bad contact or oxydation on the connector. It took me 10 minutes or so and cost 0, whereas the useless diagnosis only was almost 200€...

Am i mad about the dealership and the Subaru HQs? A little, I was about to give thousands of valuable money for nothing. They didn't take the time to think, nor probe the involved connectors and harnesses, even though they had plenty of time to do so (2 full days).

I may be the first to encounter this problem, but the way the wires are left uncovered so close to the passengers feet, I think others may run into something similar. Anyway, I hope this thread can help.