I'm currently troubleshooting my A/C which works perfectly well some of the time, but not at all at other times. My latest is that I think I've isolated it down to either the temperature sensor(s) or the ECU. Here's why: When it works, it works well. It blows nice and cold. During my last major, the shop verified the A/C worked (I'd complained of it not) and topped off or otherwise checked the refrigerant. With the engine NOT running but the ignition on, I ducked under the dashboard and watched the servo move in and out as I adjusted the climate control from Lo (coldest, 64 degrees) back and forth to Hi (hottest, 80 degrees). Interestingly though, it moved all the way to one direction when it was at Lo, and all the way to the opposite direction at any other setting (66 through Hi). It never stopped part-way. In the past, when I've been driving it around, basically the AC works when it's cool out...and I don't really need it. And it DOESN'T blow cold at all when it's hot out, when I actually need it to. So it either has bad input...or it's making the wrong decision given the input. I'm going to do some more driving around, testing its behavior in different ambient temperatures at different settings while watching the servo. In the meantime, does anyone have any advice on where to go from here? Precisely what to check and how? It looks there are a pair of 68154200 temperature sensors under the dash, and they run $40 each. The cabin air temperature sensor is 63934200, at $100. Maybe I could test that by blowing hot air on it with a hair dryer to see how everything responds. The external air temperature sensor 65889400 ($50) seems unlikely, but I guess that's one more thing to check. And I don't even want to mention the price of the ECU, with the hope that that's not the culprit.
Matt, what exactly are you looking at that is moving? There are so many servos on the evaporator unit. Some move at specific times. e.g. the car will not blow cold air directly on your face when the outside air is cold and the engine has not warmed up enough to provide hot air. Image Unavailable, Please Login Some of the temperature control valves will not be visible from inside the cabin. e.g. the TGK (hot water proportional) valve. Does your shop have any official Ferrari diagnositic equipment they can plug into the system to look for anomalies? e.g. SD2 tool? It may be a sensor issue, it may be something else. Unfortunately, I don't know how you'd test the sensors using, say a multimeter unless you had another car to compare it to ...or if the sensors were completely open circuit. Most will be simple resistive type sensors.
Thanks Ian. On that schematic, it would be where #5 is, at the bottom of the dash closest to the floor. I’m gonna go for a drive and collect a bit more data on when it does/doesn’t blow cold and will report back here. And I’m sure my shop has an SD2–maybe I’ll drive by and ask what would be involved for them to hook it up and see if it’ll provide any useful info.
#5 is the distribution motor for the foot air. I don't understand why that would move when you changed the heat setting.
It must be that when it’s all the way on Lo it closes/opens the foot air, and overrides the face/foot setting.
The SD-2/SDX provides excellent climate control diagnostics. Frankly, it's the most efficient way to diagnose the system. Octopus cable "D" through the OBD-II port.
Went for a drive this morning and it blew cold, though wasn’t very hot outside. I looked underneath again, and the servo I referenced underneath must be the recirculation. When I toggled that button it went in and out. I’ll also mentioned that after most drives I get some little chunks of foam on the floor that must be deteriorating over time. Maybe some small chance those are gumming up the airflow somewhere and interfering with sensing/control. Either way, I’m gonna keep a close eye on it, and will try to get to my shop and read things with an SD2. Image Unavailable, Please Login
Interesting. According to the manual, actuator #4 in the diagram above is the fresh air/recirculation actuator. Sounds like your system is confused. Either that or the WSM is wrong... or there is something strange about the system we are not aware of. Good luck with the SD2 diagnostics
You can try a hard reset (circuit 30 discharge) by taking both leads off the battery and jumping them together for roughly ten min, this will discharge all capacitors and modules and send the climate control into a basic settings relearn. Remember to unhook your jumper before hooking your battery back up. If your outside temp is reading the right temp in your instrument cluster then it won’t be your problem because the climate control uses the same sensor. When it’s blowing warm do you hear the compressor engaging? And if it is engaged, is the condenser fan running?
What about more common issues like failing expansion valve, moisture in refrigerant, that kind of stuff? A top off needed means slow leak and possible moisture ingress. You can get freezing in expansion valve then no cool. Varying ambient temps can assist in a marginal system failing intermittently.
Have had her out for a handful more drives in temperate (Los Angeles) weather, and it’s blown cold every time. I tried lots of different combinations of settings to try to get it to malfunction, but couldn’t. So for now, it still seems to be a thing that only happens in 90+ and sunny. Given the forecast, I might end up having to wait until next summer, which of course isn’t such a bad thing. Or if I get around to popping the dashboard off to replace the vents, maybe I’ll be able to do some closer inspections. Thanks again to all for the input in the meantime.
