So, I have a Mercedes-Benz, A140 W168. I moved to Finland about 18ish months ago which is when we bought the car 2nd hand.

Last winter temperatures only went down to around -15C (5F) degrees, and while the car took a bit more effort to start it worked every day, even without plugging in the block heater.

This year however, weather is getting a lot colder, down to -28C in the morning (-18F). Cars of my friends still start fine or with some difficulty (but still start) without block heaters, of course it is advised to plug it in. My car however, doesn't seem to do anything but light up the dashboard. Turning the ignition key all the way produced a few clicks but nothing more, after a few times there weren't even clicks anymore.

But it doesn't seem like the block heater is doing anything at all. First I thought the timer had broken (I set it in the evening so it runs for about 1.5-2h before I leave for work). Then I tried twice just plugging in the block heater from the wall plug to the front of the car, coming back 2 hours later with no noticeable heat to find under the motor hood (I just felt around with my hands). I also read that you are supposed to hear a silent sizzling sound when it is plugged in, couldn't hear this either.

When the weather warmed up a bit (-18C, 0F), I had a friend come over with his car and we managed to successfully jump-start my car by connecting his battery to mine and after leaving it for a minute or so with his motor running. I then drove around for over an hour and then successfully stopped and started at a gas station and then the supermarket.

I left it over the weekend for 2 days and tried starting with the same result as before, no noticeable heat on the block heater, no clicks at all, dashboard lit up and all the lights work as well.

Now my questions are..

  • is the problem really just the temperature of the motor? Other people's cars seem to start fine while mine doesn't even make a squeak.
  • Is it possibly a fault also in the battery?
  • How difficult/expensive is it to fix or replace the block heater?
  • Is there any troubleshooting I can do from home? (I have minimal equipment and experience, I can just about replace fuses and the tires...)

I'm not sure how to continue now except for calling a mechanic and have him come over to look at it.

1 Answer 1


A car battery's power will drop with temperature. It would be my first port of call.

Since the car ran fine when you had it jumpstarted with the help of your friend, I would have the battery tested to make sure that it can deliver sufficient juice to the starter.

  • Thanks for the quick answer. Just thinking out loud: it would make sense a colder motor needs more power from the battery to even try and start, so the combination of lowered battery power (there is probably some wear on the battery as well) and higher juice needed creates a worst-case-scenario?
    – Ward D.S.
    Commented Jan 19, 2016 at 15:03
  • @WardD.S. Yes, makes sense
    – Zaid
    Commented Jan 19, 2016 at 15:09
  • I agree on that, this was also my first thought. Around -30°C mean a lot of stress for the battery and the engine. Commented Jan 19, 2016 at 16:34
  • Sorry for late accept. I got myself a battery charger and took out the battery (surprisingly simple, glad my battery is under the passenger seat!). Left it charging overnight and some more. Weather also warmed up to -10/-5 and the car started with no issues at all. Thanks a lot for the help, hopefully this is the end of it (until next winter at least)
    – Ward D.S.
    Commented Jan 25, 2016 at 11:14

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