Pressing horn activates AC and vice versa

First thing I'd check is your 12v battery. If it was weak and you left the doors open and the interior lights on they could have run it low. When the 12v is failed/failing on a Prius the car does all sorts of weird things like you suggest.

It might not be the 12v, but it's always the first thing to look at. They're only about £95 fitted to replace using genuine Toyota parts.

 

how did you clean the a/c?

 

This reminds me of the time I had a washer fluid leak, on another vehicle. In the course of troubleshooting I took the front bumper off*, and pulled off two identical electrical connectors, one for right turn signal, one going to the wiper fluid motor.

Long story short: finally sorted everything out, got everything back together. When plugging the electrical connectors back in, it seemed like there was barely enough reach on one of them, no matter. So later, went for a drive, everything fine, then pulling back into our side street I signalled a right turn, and got rhythmic squirts of washer fluid for my troubles.

* Later found the leak, and it was nowhere near the front bumper, but hey...

 

i wonder if there's a short inside the steering wheel, or the clock spring?

 

I wonder if they used the wrong a/c lubrication oil and are now getting shorts going on in places where it shouldn't? Doesn't the Prius require a special non conductive a/c lubricant?

 

I think you've found your problem.

 

I take it that either you or a previous owner smoked in the car...

Bill the Engineer

 

i'm not sure where it would touch anything in the vents, the fan i suppose. maybe turn on a/c and disconnect horn, use fresh air, fan on high.

 

Assuming there are no holes in the vent tubing or that the spray didn't get all over the electrics internally, which it's sounding like it has.

 

I am going to out myself as a skeptic on the cleaning-foam-causation theory. There really is hardly anything electrical within the ducts and heater enclosure (aside from the PTC electric heat elements), so we'd have to walk further down the probability scale to where a bunch of foam drips out at one of the joints in the ductwork and happens to get somewhere that it can conduct between the horn and steering-wheel-control buttons. I doubt the cleaning foam actually dissolves wire insulation (you could spray some on a spare bit of electric wire and see), so the likeliest thing left for this theory would be the stuff dribbling down the wires and reaching a connector, forming a path between two or more of the pins, which are usually pretty well recessed in the connector shell. I won't say impossible, I'm trying to weigh probabilities.

bisco's "clock spring" suggestion refers to the wound-up ribbon cable behind the steering wheel that allows the wheel to turn while carring the electrical paths for the wheel-mounted controls, horn, and airbag. Your car is nine years old and those ribbon cables have been known to wear through the insulation in spots, and create weird interactions between different wheel-mounted controls. There are existing PriusChat threads about it. It's possible for such a problem to have come along independently of your AC foaming, but at just the right time to be confusing.

Typical of a clockspring problem is that how often it happens can depend on which way the wheel is pointed, or you get the classic 'horn honks every time I turn left' kind of thing. Maybe that isn't a feature in your case.

To check any of that out, you'll at least end up removing the plastic trim around the steering column. You should be able to find the connector attaching to the clockspring itself. Maybe you'll find that connector is right under a ductwork joint and it's gooey. In that case, maybe there's something to the AC goo theory after all. If not, you'd probably just proceed to examining the clockspring itself, which you get to by pulling the steering wheel.

The service manual has important words for you regarding how to do that while safely handling the airbag. Do note that any bright yellow wiring connectors you see in that area will be airbag-related.

-Chap

 

The foam startled the mouse, who ran to a different place and from nerves ate a quick wire lunch.

 

No, the clockspring is behind the steering wheel, the steering wheel nut is behind the airbag, and the clockspring is part of the airbag circuit. It's not a difficult job otherwise, just make sure you learn the precautions against accidentally deploying the bag (at close range, not good for you).

But as I suggested above, you can probably see the connections on the stationary side of the clockspring, anyway, just by removing the plastic trim around the steering column. If it has anything to do with the A/C foam, I'd think the connectors on that side would be the only ones with any chance of being near a ductwork joint.

-Chap

 

I would check the wiring harness coming off the steering wheel under the dash..it sounds to me that fluid leaked out of the ac ductwork and into the connector causing a common ground between the two circuits.(horn and ac controls) does the steering wheel still work the radio?..id use a hair dryer to get the moisture out of the connector before ripping things apart

 

I was hoping that as things dried out your gremlins would go away, but it does not seem quite that simple.

 

And the health of the 12v is what?