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  #1  
Old 19 February 2008, 08:41 AM
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Driver Turn on the headlights before starting car if it's cold out

Comment: my boss claims that in cold weather, turning the headlights on
before starting the car helps get the juice flowing, therefore aiding the
ignition system....

Is the true??

He is from Boston, and swears everybody up there knows about this??
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  #2  
Old 19 February 2008, 09:24 AM
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Quote:
Originally Posted by snopes View Post
Comment: my boss claims that in cold weather, turning the headlights on
before starting the car helps get the juice flowing, therefore aiding the
ignition system....
Over here the AA always advised NOT turning the headlights on before starting the car because the battery takes quite a hit when starting and it really doesn't need the extra load of headlights on it at that point (they don't produce their yellow handbooks any more so I can't go check if it's still current advice).

If the car has starting problems and takes lots of attempts, the extra loading of headlights will run the battery down faster than lots of attempts without the extra drain and could leave the person stranded with a flat battery. I had a chance to test this out last year while diagnosing a problem with my car - it turned out to be a malfunctioning light switch (couldn't switch the lights off) and the drain was sufficient that the car wouldn't start. Once the lights were disconnected from the circuit, I could get the car going.
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Old 19 February 2008, 10:41 AM
Troberg Troberg is offline
 
 
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Don't turn on anything that uses battery power if you can avoid it. It's not unusual to have those "three reluctant turns on the starter motor", and the headlights can be enough to stop it from starting.

Batteries don't need any spin up, they can deliver what they have immediately.
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Old 19 February 2008, 11:07 AM
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Quote:
Originally Posted by snopes View Post
He is from Boston, and swears everybody up there knows about this??
That it's a good way to stall out your car before work? Indeed we do.
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  #5  
Old 19 February 2008, 11:32 AM
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Quote:
Originally Posted by Troberg View Post
Batteries don't need any spin up, they can deliver what they have immediately.
That's incorrect. A battery that's been warmed up can provide more juice than a cold battery - and having current flow warms up a battery. Whether or not switching on the lights before starting (and presumably, turning them off while starting) works, I can't say - I'd guess not, but it would depend on how long you left the light on and how much current you were drawing out of the battery.

Henry
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Old 19 February 2008, 01:23 PM
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If I have any concerns about whether my car will start, the last thing I'd do is turn on something that takes power away.
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  #7  
Old 19 February 2008, 01:29 PM
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Most fuel injected cars can be aided by leaving the ignition on for 3-5 seconds before turning the key on to the start position. This is especially true in cold weather if the car has set for a few days. It pressurizes the fuel rail, and you don't waste time cranking the engine, while waiting for the injectors to get fuel. But that's the only thing- not headlamps. A few years ago, the Honda dealer I worked for sold "battery blankets" an official Honda accessory, that surrounded the battery, and kept it warmer during extremly cold weather to aid cold starting. Might have been useful along with a block heater in extremely cold weather, but was not very popular in Nebraska. Maybe in Alaska?
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Old 19 February 2008, 01:53 PM
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These days, most people will have already drawn current from the battery before they crank the engine. You walk up to the car and click the keyless entry (which pulses the solenoid for the power door locks, and on some cars, flashes the lights), open the door (which turns on the dome light - often on a 15 or 30 second timer), adjust the power seat, then crank the engine. The only significant power drain here is the keyless entry - as there's a very big "inrush" for power door lock solenoids, and again, on some cars, it flashes the solenoids.

In northern ontario and the northern parts of other provinces, block heaters are used all the time, and plug-ins are available in parking lots. Most, if not all cars sold in Canada, come standard with block heaters.
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Old 19 February 2008, 02:13 PM
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Quote:
Originally Posted by snopes View Post
He is from Boston, and swears everybody up there knows about this??
I am from Boston and this is the first I've heard of this. I'll have to assume that the rest of his information is equally reliable.
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Old 19 February 2008, 02:31 PM
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Quote:
That's incorrect. A battery that's been warmed up can provide more juice than a cold battery - and having current flow warms up a battery.
Even the lead accs used in cars? Dry batteries can sometimes work like that, but I've yet to see it happen on anything else.

Quote:
Most fuel injected cars can be aided by leaving the ignition on for 3-5 seconds before turning the key on to the start position.
Good point, havn't thought about that. Should work.

Quote:
A few years ago, the Honda dealer I worked for sold "battery blankets" an official Honda accessory, that surrounded the battery, and kept it warmer during extremly cold weather to aid cold starting.
Are you sure it was to aid cold starting and not to prevent it from freezing? If a battery goes flat, it can freeze if it's cold. That happened to me just about every winter with my Pontiac. Luckily, I found a place that had a two year warranty that included freezing. I even told them about the problem before I bought the battery, and they still stood by their battery warranty. Probably cost them about five batteries...

Quote:
The only significant power drain here is the keyless entry - as there's a very big "inrush" for power door lock solenoids, and again, on some cars, it flashes the solenoids.
It draws a lot of current, but only for a short moment.
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Old 19 February 2008, 02:35 PM
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Quote:
Originally Posted by Troberg View Post
Even the lead accs used in cars? Dry batteries can sometimes work like that, but I've yet to see it happen on anything else.
Shoot, you know what? I don't know that it does apply to wet batteries. More research is needed - off to Google I go.
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Old 19 February 2008, 02:42 PM
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Quote:
Originally Posted by niner View Post
Shoot, you know what? I don't know that it does apply to wet batteries. More research is needed - off to Google I go.
Yes it applies to wet batteries.
Richard the electrical engineer with experience in telecon facilities having tons of wet cell battereis.
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  #13  
Old 19 February 2008, 04:29 PM
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Nope, turning on the head lights would be the last thing you would want to do, all it does is draw current and capacity from the battery.

Turning the headlights on is sometimes used as a "no tools" check of why a car won't start.

A simple troubleshooting guide for non-starting;
1. Car cranks OK but won't start. Battery, starter etc. are OK. There is a problem in spark or fuel supply.

2. Car won't crank or crannks slowly.
Turn on headlights and try to start the car.
If the headlights dim or go completely off then the battery is most likely dead.
If the headlights don't dim then the battery is probably OK and the problem is in the ignition switch, starter relay or starter motor.


Car batteries loose a lot of power as the temperature drops. At -20F they will typically have only about half the available power as they do at 70F. The main purpose of a battery heater is to keep the battery warm. If the heater is keeping the battery from freezing then you either need to recharge the battery or move to a place that isn't so freakin cold.

A lead-acid battery won't freeze if it is fully charged. (A fully charged battery won't freeze until the temperature drops below -70F or so). A partially discharged battery will freeze at higher temperatures. A battery with a very low charge may well freeze at temperatures above 0F.
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  #14  
Old 19 February 2008, 05:16 PM
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Quote:
Originally Posted by Hero_Mike View Post
.In northern ontario and the northern parts of other provinces, block heaters are used all the time, and plug-ins are available in parking lots. Most, if not all cars sold in Canada, come standard with block heaters.
Same in places like Minnesota. Diesel cars around here would usually have the plug in as well (for the glow plugs I suppose)-I worked with a woman who had a diesel Golf, and she'd get a spot by the side door and run an extension cord into the building.

I've had some issues in very cold weather (ten below zero or more)-if my car sits all night then there's a chance it won't crank over fast enough in the morning. I discovered that if I went for a drive every four or five hours it would start right up the next morning.

Regarding the OP, my Dad always taught me to shut everything off when you stop your car-lights, radio, heater fan, and....well that's probably about it.

-Doug

Last edited by Roadsterboy; 19 February 2008 at 05:18 PM. Reason: Pressed send too soon
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  #15  
Old 19 February 2008, 05:56 PM
Natalie Natalie is offline
 
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Quote:
Originally Posted by Roadsterboy View Post
Same in places like Minnesota. Diesel cars around here would usually have the plug in as well (for the glow plugs I suppose)-I worked with a woman who had a diesel Golf, and she'd get a spot by the side door and run an extension cord into the building.

I've had some issues in very cold weather (ten below zero or more)-if my car sits all night then there's a chance it won't crank over fast enough in the morning. I discovered that if I went for a drive every four or five hours it would start right up the next morning.

Regarding the OP, my Dad always taught me to shut everything off when you stop your car-lights, radio, heater fan, and....well that's probably about it.

-Doug
Huh, I'm from Minnesota and I didn't know that some cars here needed battery heaters. I have a good friend who transferred to University of Alaska - Fairbanks from a college in Minneapolis. Her welcome packet suggested that students with cars should purchase heaters, and I think all of the slots in the parking ramps on campus have a plug, so students can plug in the heater. Neither of us had ever heard of that before, but then again we don't drive diesel cars.
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Old 19 February 2008, 05:57 PM
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Quote:
Originally Posted by Roadsterboy View Post
Same in places like Minnesota. Diesel cars around here would usually have the plug in as well (for the glow plugs I suppose)-I worked with a woman who had a diesel Golf, and she'd get a spot by the side door and run an extension cord into the building.
Years ago, one of my co-workers had a Golf diesel and claimed that the glow plugs were tied to the door lights - that when you opened the door, the glow plugs would come on and by the time you sat down and settled yourself to start the car, it would be ready to go. No idea if it's true, but if it is tied to a temperature sensor, it makes sense.
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  #17  
Old 19 February 2008, 06:28 PM
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The auto help columnist for our local Daily Blab is a man by the name of Paul Brand. I know him personally, we're both die hard gear heads. He's helped me with a lot of different problems over the years. He's sharp, and knows his stuff.

He just addresssed this very question a couple of weeks ago in his column.

If you can't pull the column up without signing in, in a nutshell, he says the legend is true. He said if you turn on the headlamps for 10 seconds, it has the effect of warming up the electrolyte, giving you a bit more cranking amperage for getting the car started on very cold mornings.

For my own part, my Buick Regal (Which is always parked outside in the winter.) has a remote door lock system. When you unlock the doors using it, the headlights come on and stay on until you open the door. In my case, since I hit the fob just as I walk out the front door, the lights stay on for about 10 seconds. I've owned this car for four years now, and it has NEVER failed to start in the coldest of weather, including a couple of weeks ago when the temp hit -18F.
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Old 19 February 2008, 10:05 PM
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Quote:
Years ago, one of my co-workers had a Golf diesel and claimed that the glow plugs were tied to the door lights - that when you opened the door, the glow plugs would come on and by the time you sat down and settled yourself to start the car, it would be ready to go. No idea if it's true, but if it is tied to a temperature sensor, it makes sense.
Uhm, no. The glow plugs would warm up when the engine was off, the key in the ignition on setting but not on start. The dashboard would show a yellow light to show that the glow plugs would be warming up, and once that light went off you would start.
Yes, I had two Golf Diesels myself, thus I actually know this time what I am talking about.

ETA: At least it was that way in the Golf IA Diesel, Golf IB GTD and Golf II GTD and Golf III TDI variants, as well as the Passat TDIs
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Old 20 February 2008, 03:43 AM
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Quote:
Originally Posted by RobDBlackwolf View Post
Uhm, no. The glow plugs would warm up when the engine was off, the key in the ignition on setting but not on start. The dashboard would show a yellow light to show that the glow plugs would be warming up, and once that light went off you would start.
Yes, I had two Golf Diesels myself, thus I actually know this time what I am talking about.

ETA: At least it was that way in the Golf IA Diesel, Golf IB GTD and Golf II GTD and Golf III TDI variants, as well as the Passat TDIs
Thanks for the info - his Golf was a 2nd generation from the mid 80's and well worn when he told me this, back in 1997. It died shortly thereafter when it needed a new fuel shutoff solenoid, which proved to be the straw that broke the camel's back, in terms of keeping this car roadworthy.
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  #20  
Old 20 February 2008, 04:11 AM
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From Dr Rocket's link:
Quote:
Why? That 10-second current draw to operate the headlights can actually warm the electrolyte in the battery a bit, helping it deliver a bit more cranking amperage -- maybe just enough to make the difference between the engine starting -- or flooding.
I'm going to have to expose my ignorance on the subject and ask, what's the difference between the first ten seconds going to the lights and the first ten seconds going to the starter? I guess the starter uses a bit more electricity but shouldn't the first turnover also warm the battery a bit, in addition to warming the engine a bit? I'm having a hard time understanding the logic of this.
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