Unexplained: Dark Mysteries of Auto Behaviour

So, I use my key-fob and remote open my car, start it up and begin driving. The CD will start up halfway through whichever track was pounding through those eight awesome Phillips speakers when the engine was cut, unless I had changed to a radio station some time yesterday. Whatever, the routine doesn’t really change, everything in the car is left as it was when I parked up the night before.
But, for whatever reason, and I’ve only noticed it in the last week or so, the heated rear screen will be on. I certainly didn’t have it on yesterday, and with the outside temperature being a balmy 10°C, it’s not as if it would come on automatically, would it? I mean, even the benevolent spirit of Joe Lucas, patron saint of shonky electrics who stands watch over anything bearing the Viking longship emblem, wouldn’t be so perverse as activate a heated rear screen in the peak of the British springtime.
Does your car do stuff that you absolutely can’t explain?

There may well be a paragraph hidden deep within the rich, leatherbound volume that is the Rover 800 owner’s manual which explains this mysterious phenomenon. I know the rear screen works, it defrosts my screen with aplomb on those days where it’s needed. Perhaps it’s so confident in its own excellence that it self-activates in the hope that there may still be ice, so I can be impressed by it once again. Perhaps I should provide it with some ice from my freezer, just to keep it happy.
The Auto button on my dashboard is supposed to mean Automatic Temperature Control, not automatic everything. I still want to make some choices for myself. Is an over-insistent heated rear screen just the tip of the iceberg? Perhaps one day my car will decide it no longer wants to take me home, and instead wrestle control away from me and force a tour of all the beautiful scenery it has heard of but never been taken to see. Rover became self aware on the 31st March at 2:14am.
What peculiar habits does your car have, which are charming but need to be kept in check in case it starts to get the upper hand?
(All images, including the one of my heated rear screen, are mine. Copyright Me and Hooniverse 2015, though I doubt very much anybody will want to use them. I must dust that dashboard)

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  1. P161911 Avatar

    On most cars, when you shut the car off with the wipers on, the wipers go off. Not on my old 1987 BMW 325, after some intermittent period of time the wipers would come back on. This car also had a strange mystery electrical drain (dead battery in less than 1 hour) that I finally solved by just installing a battery shutoff switch.

    1. nanoop Avatar

      Draining a healthy battery in one hour is easy to diagnose: find the hot part and replace it…

      1. P161911 Avatar

        It was hidden somewhere deep inside the car. Car is long gone now.
        I’m convinced Joe Lucas and Robert Bosch are brothers.

    2. Closed 24/7 Avatar
      Closed 24/7

      When turning the wipers of my Lancia Kappa off or lowering their speed, they will wipe one last time before doing what I told them, as if to say “we heard you, but we can still move if we want to”. I know it’s meant to confirm the change, but it can be really annoying when I’m turning them off because the windshield is dry and they scrub over the dry glass unneccessarily.

  2. Tiberiuswise Avatar

    I am an avid non-door-locker. Seriously, I almost never lock my doors. Many new cars have a feature where the doors lock when you put the car in drive. I always defeat this.
    Now they came up with a new one. Some cars with the keyless fob will automatically lock the doors when you exit the vehicle and take the fob with you. This happens intermittently with no rhyme or reason that I can detect. Very frustrating when you get out and then go to get something out of the back seat. I have yet to figure out a way to defeat this.

    1. Manic_King Avatar

      In VW cars you can chose: lock the doors by wiping small square on the door handle (like I do) or after which car-to-key distance door locks autom. and opens autom when you approach it. If you choose touch- locking/unlocking then door stays unlocked when you leave and don’t touch it. It’s somewhere in the menus.
      Mystery: Same VW though has e-handbrake with autom. engagement which has logic I don’t understand. Waiting boom to open? 2 times from 10 car dries to drag its rear end as e-brake is activated automatically.
      Mystery2: VW has this creepy driver monitoring system, it will show nice cup of coffee on small screen in dash when it thinks driver is tired, I have seen it once, no idea what’s the logic behind it.

  3. Frank T. Cat Avatar
    Frank T. Cat

    It might not be the same on your Rover’s rear window defroster, but my SAAB 9-5 turns the heated mirrors on automatically when it’s <=1C. At least according to the automatic climate control technical brief I read.

    1. Rust-MyEnemy Avatar

      I’ve never worked out if my heated mirrors actually work. Hell, it’s a Rover. They must!

    2. ptschett Avatar

      My new Challenger w/ auto climate control has a similar idea about automatically activating the heated mirrors and the rear window defroster on cold mornings.

  4. peugeotdude505 Avatar

    On the wife’s Mitsu Galant ( yes, I own a galant ) the A/C will turn itself on when you start the car sometimes. No idea

    1. JayP Avatar

      My 2001 Mustang did that- to cycle the compressor to keep it working properly if it hadn’t been used in a while.

  5. ramLlama Avatar

    My Volvo has automatic headlights. I love automatic headlights!
    Thing is, there is *no* way to turn off all the lights (including DRL’s), even if the switch it at ‘0’. Indeed ‘0’ just means ‘auto’ unless you reprogram the computer to disable automatic headlights. So, if you were, for example, waiting for someone to come out of the grocery store at night and you don’t want to keep the lights on…you have to pull a fuse.
    Why Volvo decided against adding one more notch for “all off” is beyond me.

    1. Frank T. Cat Avatar
      Frank T. Cat

      SAAB did the same thing in the 90’s and early 2000’s on the NG900, OG9-3 and OG9-5. The headlight switch does nothing to turn the lights off, even in the OFF position. If you pull the DRL fuse, however, the headlight switch functions normally. One thing you don’t need to break out the Tech-II for.

  6. Kiefmo Avatar

    When I turn on the HVAC fan or the rear window defroster in my W126, the tach suddenly starts working. No clue about that one — as far as I know, they aren’t on the same circuit.
    The left, but not the right, turn signal flashes too fast and dim. All of the bulbs are good and blink, just at half brightness and double time. They all flash at normal brightness when using the hazards.
    The intermittent wiper control is itself intermittent in operation.
    When the humidity is above a certain level, the power lock switch in the driver’s door cycles endlessly, running the little pneumatic pump in the trunk to cycle the doors, trunk, and fuel door open and closed endlessly. The pump has therefore been unplugged to preserve the battery and secure the car.
    The trunk is permanently locked and can only be opened using a drill bit inserted just the right way into a hole drilled into the plastic bezel on the right of the trunk lock.
    Also, when I changed the power steering pressure hose on the family Ody last night (4.5 hour job — thanks Honda for making that flare nut so inaccessible), I had to transfer a switch on the hose which apparently turns off the A/C when the car is turning. Why on earth is that necessary?

    1. ptschett Avatar

      I’m guessing that the Honda’s accessory drive belt design can support either the air conditioner compressor’s load or the power steering pump’s load, but not both at high loads at the same time; if so, it would make sense for steering to get the priority.

      1. Kiefmo Avatar

        I guess that makes sense, but I wish it could be sufficiently… frictiony(?) to run both at once and reduce complication. I’m sure friction is the issue, as it’s hard to believe that a 3.5L V6 would get bogged running them both. One of Honda’s wee I4s, on the other hand — I can definitely see it getting bogged.
        Having dealt now with hydraulic power steering repair — I want my next new-ish car to have electric.

    2. Manic_King Avatar

      On very simple old cars, like say seventies’ Fiats, that turn signal action meant that ground was bad/missing in one of the lights, check the bolts/studs which hold turning lights to the car body metal, under one of these should be (probably black) wire which needs to be properly grounded.

      1. Kiefmo Avatar

        I figured it would be a grounding issue somewhere. I just haven’t bothered to try and track it down yet.

    3. Frank T. Cat Avatar
      Frank T. Cat

      bad grounds,
      bad grounds,
      whatcha gonna do,
      whatcha gonna do,
      when current flow through you.

  7. P161911 Avatar

    I work with a woman that has a Ford Explorer (that she named Dora), that has started doing things like randomly moving the power seats while she is driving. She is only about 5’2″ so it could be a real problem if she can’t reach the brakes. I think it has done other things like randomly raise and lower windows and randomly stop the engine. She has taken it to three different shops with no diagnosis yet. She has stopped driving Dora.

    1. salguod Avatar

      That sounds like water in the fuse box. One common complaint on the forums for the GMC Acadia and the like are odd electrical things like this, typically cars that won’t shut off. Early sunroof equipped models would leak and funnel that water down the A pillar into the fuse box, causing all kinds of gremlins.

  8. Citric Avatar

    On the Toyota Matrix I had there were automatic headlights. Except I didn’t actually know they were installed – it wasn’t mentioned in any of the sales materials, it’s was not actually demarcated by a switch – the stalk just said off, parking, on – and the only reason I found out is because I was driving down a shaded street and they kept going off and on, and I couldn’t figure out why my gauges kept dimming for no apparent reason. Eventually I figured it out, it was still weird.

  9. Fuhrman16 Avatar

    The cruise control on my Neon can be a bit temperamental at times. Sometimes when you hit the resume speed or the cancel button, it will shut off completely. It typically only does it once on the way home, though it has started to do it in the mornings as well. When it first started doing it, I figured it was driver error, me absent mindlessly hitting the wrong button, but no. Now it’s just another small annoyance in my daily commute.

  10. David Avatar

    My first car was a 1959 Nash Metropolitan. It had many quirks, but one that fits this category was that using the turn signals caused the radio to ‘blink’ along with the lights. On/off/on/off.
    Many years later, a 280Z we had made me hate night driving because if the lights were on and I had to hit the brakes hard, the fuse controlling the taillights would blow. Every. Single. Time. Leaving no taillights, signals or brake lights. Nobody could figure it out.

    1. Fuhrman16 Avatar

      My radio in my old van had the same issue. Turns out it the 12 volt power wire was spliced into the turn signal wiring.

  11. Pete Z. Avatar
    Pete Z.

    Does your 1970 280SL (113 model) engine keep running after turning off the key with the l/s door open ? Try filling up the brake fluid reservoir so the low level warning floats break contact stopping a feedback issue in the system. Trust me.

    1. econobiker Avatar

      And those wonderful 1980s Dodge/Plymouth twins Omni/Horizon with the 2.2 engine that would run on after shut down when the A/C compressor was taken out of the circuit. It seems that Chrysler used the A/C compressor to stop run on by engaging it momentarily upon shutdown. Once the quality compressor gave out and when installed a smaller accessory drive belt to bypass that non-functioning heap of metal, the car’s engine would embarrassedly run-on after shutdown. (And to note, they did something different to stop the engine run-on for the few non-A/C equipped cars from the factory.)

  12. spotarama Avatar

    on a recent country journey in the Holden Clown Car (Rodeo by any other name), we went from a 110kmh zone back into an 80 so i tapped the brakes to turn off the cruise control, it slowed to a bit over 80 then decided i didn’t know what i was doing and floored itself……the auto changed down straight away and off we went at full throttle straight back past 110 and it was doing over 120 before i worked out what the hell was going on, i hit the brakes hard and it behaved itself. hasn’t done it again since but there again i haven’t used the cruise control again since

  13. Dean Bigglesworth Avatar
    Dean Bigglesworth

    The in-dash cd changer in the Focus would often jam and stop playing if I hit a pothole. Then some weeks later I’d hit another pothole and it’d continue where it left off.