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Headlights on, engine off!!
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lbl
New User
Apr 4, 2009, 10:09 AM
Post #1 of 6
(2879 views)
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Headlights on, engine off!!
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I just heard from my son and he said if he turns the headlights on before he starts the engine, the engine will in fact start.
(This post was edited by carjunky on Nov 10, 2014, 1:47 AM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 4, 2009, 1:12 PM
Post #2 of 6
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Re: Headlights on, engine off!!
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?? Do you like this car other than that? This might be simple. Headlights are a fairly big draw and there are grounds from engine block (where battery's main ground is) to jump (look like insulation free straps) to link block/trans axle to the body. What may be happening is too much of limited ground is used up for headlights such that engine controls don't get their share of the pie!
Before you go too nuts if you want this car - try jumping yourself (use good jumper cables for test) from solid ground on engine to something significant on body. If the problem quits with that then this isn't that bad and just needs a ground strap fixed or cleaned up.
If you want out check now with your Florida DMV for your rights as the car is rendered unusable as it is and your right to cancel a sale varies widely from state to state. Call your insurance agent if need be or better yet call the person you bought the car from and see if they fix that.
Up front it's not a mistake to make a private purchase and some dealers will allow their employees some trades to resell on their own or keep. Most new car dealers aren't too interested in cars over say 6 years old and 60,000 miles or so so they wholesale those - doesn't mean they are bad just the dealers generally keep the highest end used cars and do get top buck.
My state has a "Lemon Aid" law but it's a real pill as first you have to get a rejection sticker, then find out the cost to make is pass and at your call would have only the amount over 10% of the selling price then can take actions. Here - you've already paid sales tax, $50 for a title and the registration which is a nightmare to recover. I think cars over 10 years old are exempt from recourse if privately sold. Dealers have a different set of rules.
Seriously - this may not be that big a deal to fix. If you've simply changed your mind on this car I'd say you are out of luck. Time to check a car is pre purchase not after.
Good luck. See if you can work it out with the seller,
T
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lbl
New User
Apr 4, 2009, 2:00 PM
Post #3 of 6
(2861 views)
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Re: Headlights on, engine off!!
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Hi Tom
Thank you very much for the reply. If possible can you clarify for us non car people what you meant (step by step) on jumping your own car??
Feel free to really "dumb it down"!!!
Should he also check fuses, etc.?
Again, really appreciate your reply and expertise.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 4, 2009, 2:57 PM
Post #4 of 6
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Re: Headlights on, engine off!!
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No need to "dumb it down" -- I would be the dumb one if I couldn't explain the basics of what is THE highly likely problem.
Basics that apply to about anything that is electric start "engined" anything!
1. The most load a battery will face in most electric start things is the starter motor. You may have notice when looking at batteries for sale they boast things like "Cold Cranking Amps" as a way to express the actual horsepower of the battery to crank an engine vs kick start, pull start.
* With that the common design is to feed the starter motor with the best connections. The battery is the source of that power and gets the heavy gauge cables direct to it and starter motors are attached to engines so there's the ground. Positive voltage goes TO an item but must return to the battery and nothing is going to do better than the weakest link - just like a chain being yanked on.
2. Now - because engines are a vibrating assembly the vehicle will be isolated by rubber mounts for the drivetrain and rubber doesn't conduct electricity for the return. To save always having to use two wires the body metal is grounded via wire straps from engine block (the major hunk of metal) to the body in several places.
3. These straps - an example shown below,
Just make the loop back to the engine block to the battery as must happen for other things in the car/vehicle to work. Frequently just bare braided wire with eyelet ends as shown.
4. These connections at the eyelets can just corrode or get broken with engine vibrations or when a car has had service they might be left unhooked.
* What I was thinking is since headlights take some substantial power that they are using up too much of the available power from where they are grounded to the body metal AND important items that control the engine that are also sharing body ground don't get adequate ground and can't make spark for ignition or perhaps empower a fuel pump (almost all are electric now) so the engine would quit running.
** If you just added grounds with jumper wire (thickness ((gauge)) counts) from engine heavy metal item to something metal that is universal to the body it may just snap to and all work nicely.
An analogy would be thinking of it like water consumption thru a garden hose. You put a sprinkler on one hose and it's happy. Put 10 sprinklers on it and none are thrilled. Bust one wide open and none will work as all the water flows thru the broken one - does that draw a mental picture for you?
The brains (computer controls) for how your engine runs are likely to be grounded to the body metal and if the headlights are hogging all the return ability they won't be able to work - hence a "no run" situation.
THE TEST: If you jumpered ground to ground without knowing if or where a weak spot was things MIGHT behave and then you would know this is a simple problem as things go for a car. Back to the analogy - the ten sprinkler heads with one using all the water such that nine don't work for diddle would behave if you kinked the hose to the broken one.
More: We know there's enough power as the engine started so it just came to my mind that it couldn't return back thru the body the energy needed as the flow of power is limited to the weakest link.
Adding a link could show this is the trouble area and then go find a broken or corroded ground if the trick works - sometimes just adding one is simpler than chasing thru the whole car as they put those ground straps in a lot of places.
Hope that didn't just confuse you all the more. I'll try harder if needed.
Side note: Folks don't always realize how much energy is used to power things in a car. A simple radio light is near nothing. A blower motor used some more power. Headlights use quite a bit - perhaps 60 watts each which if you were pedaling a generating, stationary bicycle to make them light would have you in a full sweat in no time!
Just know that any power consumed must return to the battery or the link breaks or is too weak to be funtional,
T
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lbl
New User
Apr 4, 2009, 3:12 PM
Post #5 of 6
(2849 views)
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Re: Headlights on, engine off!!
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Again, I thank you for taking the time to help us out. I just heard from my son and he said if he turns the headlights on before he starts the engine, the engine will in fact start. Does this prove your theory to most likely be the problem? Thanks again, L
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 4, 2009, 3:31 PM
Post #6 of 6
(2836 views)
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Re: Headlights on, engine off!!
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Sometimes goofy things happen when you run an added load before the larger load coming. The weak spot gets red hot and might make a better connection for the moment AND if cool where this car is a quick energy draw warms up a battery so available amps could (note COULD) be higher for a short while.
I'm still stuck on a connection theory and hope I haven't cause a wild goose chase,
T
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