Yet another car starting thread

[sneek]

Hi Guys,


A good friend called me this morning telling me her car wouldn't start. I was wondering if anyone knew what they best course of action would be. First off the car's hood is frozen shut, so I was thinking of taking some warm (not hot) water and pouring it around the edges of the hood to get it open. I was planning on keeping it open for a bit to make sure that the water wouldn't freeze the car shut. Then I was planning on taking the battery out and putting it on a charger for a couple hours to see if it would take a charge. Would this be a good idea, or would it be a better idea to just jump start her car? I mean it really only has to hold the car until we throw a new battery into the car, so I know that jump starting would probably be a better solution. Another issue is that she doesn't have a garage, and charging a car battery inside of an apartment isn't exactly the greatest idea either, just in case the battery is frozen. Conversely, jump starting, to the best of my knowledge, can cause harm to the donor car (mine), and I defiantly don't want that.

any opinions would be appreciated.

[dj_honda]

hood frozen: brush away all the snow, and break off all the ice you can, then take something rigid and plastic and carefully pry the hood up (after unlatching it), until it is fee enough to pop the latch.


make sure the terminals on the battery are tight....lots of people think their batteries are dead when its just that the terminals are not tight or have lots of corrosion. just clean them up, make sure they are ttight etc.

jump starting it, if performed correctly shouldn't harm your car.

[Tomaz]

please see other threads

[GTI CANADIAN]

Flame-Thrower.

[sneek]

I searched the wrong section. My bad!

[drtoohotty1]

is she hot??? letting us know if she is or not and posting pics would be your best course of action

[Swank]

Hint; park facing south! The winds from the north can often make a serious difference on windy days when it's blowing directly on your engine for hours on end, that's where the bitter cold misery comes from.

[realazy]

I thought it has been discussed here many times that wind chill does not affect objects.

Picture a thermometer, it only reads the ambient temperature.

Living things produce heat, and the wind will strip heat away faster because of the higher heat transfer coefficient from convection.

The wind chill reading is just the temperature at what the wind would "feel" like if it was just an environment without wind.

For a car, the wind would strip away the heat faster than usual, but once the car is at ambient temperature, it can no longer get colder.

In the example that the car was parked for 6-8 hours, there is no difference between wind and no wind.

[Swank]

I think that's only correct with 0% humidity; evaporation causes a temperature drop, and increased air flow speeds evaporation.

[realazy]

Which at -40*C the humidity is extremely low and close to 0%.

[Swank]

Originally posted by realazy

Living things produce heat, and the wind will strip heat away faster because of the higher heat transfer coefficient from convection.

For a car, the wind would strip away the heat faster than usual, but once the car is at ambient temperature, it can no longer get colder.

In the example that the car was parked for 6-8 hours, there is no difference between wind and no wind.

Block heaters and sunshine on dark paint aren't living things, but they sure yield heat, and you wouldn't want that heat stripped away by the wind, especially over the course of 6-8 hours.

The humidity over the last 24 hours has been averaging about 90%.

[realazy]

I agree the heat generated by sunlight and block heaters will be affected by wind. But if it's at night and the block heater is on, will the effect be noticable?

I'm pretty sure you are talking about 90% relative humidity. At temperatures below -20*C even at 100% relative humidity you are looking at basically no water vapor in the air.

Graph I stole from wikipedia:

[alloroc]

It doesn't matter how much moisture there is in the air. Your car will only cool down to the drybulb temperature.

Let me explain how RH is determined.
To determine relative humidity you need to take two temperature readings drybulb (the thermometer you are used to using) and wetbulb (determined by using a sling psychrometer) By measuring wetbulb and drybulb then plotting on a psychrometric chart (similar to what realazy posted - only with more lines you can determine the RH.

You car, radiator engine and every other dry object in the universe will only get cooled to the 'drybulb' temperature this happens to be the same temperature they announce on the radio. If you leave your car sitting for about 6 hours even with no wind you can pretty much count on everything under the hood being at ambient (drybulb)

Windchill is something else all over again an is actually a combination of two things -

-Because your body is producing heat if you stand still on a windless day you willl be enveloped by a small layer of air R value of about 0.75. How easiliy this thermal layer is broken down by wind is dependent on a factor called 'emmisivity' and is part of the reason why when a fluid is in motion around an object the heat transfer rate is increased (yes, air is a fluid)
-The second consideration of wind chill is the effect of the wind on moist objects (wetbulb temperature mentioned above) -skin and pores sweat and therefore are subject to loss of latent heat (cooling through evaporation).

Both of the above considerations are used to estimate 'windchill' which is used to calculate first how cold it 'feels' ie how you feel on a windless day, and more importantly in our climate how quickly you could get frostbite.

[gonein10]

haha i love this conversation! started over someone asking about a dead battery!!

[Swank]

Originally posted by realazy
I agree the heat generated by sunlight and block heaters will be affected by wind. But if it's at night and the block heater is on, will the effect be noticable?

Oops, that may be the discrepancy here, I meant in the daytime. Some good point tho realazy, and you're right, once the engine has reached ambient temp, it's not getting any colder from wind. But sheltering the engine from the wind with the car itself can slow the engine from cooling down as a result of wind blowing on it, it also reduces the efficiency of warming up the car. I do find the effect noticeable, and in previous cars it's made the difference between starting and probably not after a day at work. At least it's free to try out for yourself.

[benyl]

OP: Boost the car. It will have no effect on yours.

[sneek]

Originally posted by benyl
OP: Boost the car. It will have no effect on yours.

Thats what I am thinking, I am just hoping it won't drain down my tiny little battery too much! I am also rather worried about boosting a frozen battery. I think I will take the battery in to warm it up first, test it, then see what to do from there. I am pretty sure the battery isn't frozen because the electronics still work.

Anyways I will let you guys continue your debate on windchill.

[benyl]

Keep your car running.

By connecting your car to the frozen car, you will start charging the battery effectively warming it up. No need to take it inside.

[Swank]

Sorry OP, I'm out.