Is This True ?

[caryc]

I can't really remember where I heard it now but someone said that you should never work your vehicle's power windows with the engine off.

Anyone know why this would be true?

 

[Cholo]

I've done it all my life. I call BS...

 

[sfhogman]

No reason. Years ago, if you left the ignition on in order to run accessories, you ran the risk of burning your points (remember those?). This was if the switch wasn't in the Accessory position. I talked to a auto (Ford/Lincoln) mechanic friend about it and he said not to worry.

Jeff

 

[Bob Wright]

My ignition switch has an "ACC" position to operate power accessories without the engine running. I would assume that would include power windows as well. Nothing in my owners manual to the contrary.

Bob Wright

 

[rugerguy]

can't see why not, they run on electric, not gas....... 8) :roll: :wink:

 

[caryc]

OK, I don't think they make a vehicle now days that doesn't have an accessory position on the ignition switch.

But from what I can remember it had something to do with the window motors running right off your battery verses them running off the alternator.

 

[Acorn]

Only reason I seed would be that it could possibly hurt is it could kill your battery.

 

[Kevin]

Did you get a new car? Both my car and my wife's you can turn the car completely off, and the windows will operate until you open a door.

Along those same lines, I've heard, not sure if it's true or not either, but what about turning off the A/C before shutting off the engine. Then the reverse, waiting for the engine to be running before turning on the A/C.

 

[m657]

go back a bit more.....a couple of my Cadillacs (1947 & 1951) had hydraulic power windows, seats and top.....none of that would work without the pump running, which was a high-draw item that would deplete the starter battery in short order if operated without the engine running

 

[EVILDOCTOR235]

I have seen several coils explode on older cars when the ing.switch was left on too long without starting the engine.I have had it happen to me.


xxxxxx

 

[Montelores]

If I'm not mistaken, all electrical demands in a conventional auto are powered by the battery (except for some internal functions of the alternator).

The battery supplies the electricity; the alternator re-charges the battery.

Monty

P.S. The highest electrical draw item in your car will be the starter motor.

When you turn your key to "Start," almost all other non-engine high-draw electrical items will have their power removed. Fan, headlights, power windows.

The "Start" position opens the circuits for other electrical items, so that all the battery's energy is available for the starter motor (and ignition, fuel injection, engine sensors, lights, gauges, etc.).

Returning the key to "Run" after engine start will re-power the non-engine circuits.

 

[RugerHound]

The only risk to the power window motors is low battery voltage. Low voltage drives current up and creates a lot of heat in electric motors. Just be cautious to not overdo it with low battery voltage.

In fact, my 2004 Ford T-Bird power window motors run each time the door is opened & closed. (They drop a quarter inch or so when open, then re-seal (rise) when he door closes)

 

[bobski]

so let me get this straight. you crash and your car is on fire....and you need to get out the window....but the car isnt running. you got to start the car first?

makes me wonder does anyone still make crank windows anymore?

 

[Pat-inCO]

so let me get this straight. you crash and your car is on fire....and you need to get out the window....but the car isnt running. you got to start the car first?

I see why you would be concerned. So many people that are involved in a collision
make sure they turn off the ignition just before the crash. :roll:

 

[Ale-8(1)]

If I'm not mistaken, all electrical demands in a conventional auto are powered by the battery (except for some internal functions of the alternator).

The battery supplies the electricity; the alternator re-charges the battery.

Monty

BINGO!

:mrgreen:

 

[caryc]

If I'm not mistaken, all electrical demands in a conventional auto are powered by the battery (except for some internal functions of the alternator).

The battery supplies the electricity; the alternator re-charges the battery.

Monty

BINGO!

:mrgreen:

But there's more voltage going into the battery when the engine is running. There will be over 14 volts at those cable ends instead of a little over 12.

Lower voltage, more amperage to run the motors?

 

[Dan in MI]

NO issue at all.

As far as more power going into the battery while running that is not true anymore depending upon vehicle and operating conditions. Most newer cars now have "smart" alternators. They only operate above 12v when the battery State of Charge (SOC) requires charging or there high loads on the engine. This is to reduce load when possible thereby increasing MPG.

The comments about older cars cooking points in "run" vs "accsy" are true. There really is no difference between those positions now and running the accessories with the engine off are no problem. Yes, it draws off the battery but unless you are running stuff for a long period of time or have weak battery it does nothing bad.


Regarding cars that the window drops and then raises while getting in or out. That is because the window is captured by the body and needds to drop to allow the door to close properly.

 

[Rick Courtright]

As far as more power going into the battery while running that is not true anymore depending upon vehicle and operating conditions. Most newer cars now have "smart" alternators. They only operate above 12v when the battery State of Charge (SOC) requires charging or there high loads on the engine. This is to reduce load when possible thereby increasing MPG.

Hi,

Dan, I realize what you're saying is correct in today's world, but from a lay person's point of view, that's just the dumbest kind of engineering I can imagine IF truly improving fuel economy's the goal!

Cutting a square foot or two off the frontal sail of ever "fatter" vehicles, finding somewhere else to drop a couple of pounds than by using smaller brake rotors, or, heaven forbid, reducing the ever increasing HP output of so many already overpowered engines--seems these would be better starting points than adding more electronics to already overly complex electrical systems...

Guess that's why nobody called me up this morning to ask how to design their next car, huh?

BTW, have the newer batteries broken the chemical "law" that healthy wet cell batteries produce 2.2v per cell, making a fully charged "12 volt" battery actually read 13.2 volts on a meter?

Rick C

 

[caryc]

OK, lots of window experts here. So tell me, why do the windows go up faster with the engine running.

Please don't tell me I have a low battery. It's a new battery about 4 months old and the windows have always worked faster with the engine running.

 

[coach]

The alternator puts out about 14+ volts when running. The battery only puts out 12 volts or less on its own. So the windows run a bit faster with the engine on.

 

[caryc]

The alternator puts out about 14+ volts when running. The battery only puts out 12 volts or less on its own. So the windows run a bit faster with the engine on.

I know that. But on one of the posts here someone said that the new smart alternators only put in 12 volts when recharging. I guess I have a stupid alternator.

 

[Rick Courtright]

I know that. But on one of the posts here someone said that the new smart alternators only put in 12 volts when recharging. I guess I have a stupid alternator.

Hi,

Cary, you may be surprised to find your relatively new battery may not be fully charged, too, regardless of smart or dumb alternator! A counter salesman told me a few years ago I should put my "brand new" battery on a trickle charger for a while when I got it home to get it "really" fully charged. Helps the battery last longer, according to him. So far, across 3-4 batteries, I think he was right...

I got one of the "Battery Tender" chargers a couple of years ago, which are much "smarter" than my old trickle charger, and it's surprising to see how long it can take with some batteries before the red lights turn to green. Even my daily driver may take 3 or 4 hours, and its alternator hits the regulated 14.5v at a whisper above idle, even with everything electrical "on" that can be. The others, which may only be driven once or twice a week, and have more miles on their alternators, can take 12 hours or more!

Rick C

 

[coach]

All alternators put out 14+ volts to charge a battery. They are regulated to the amount of amps supplied to take care of any loads. Smart or not, recharging takes more than 12volts. Battery tenders and other high tech chargers have electronics that vary, pulse or otherwise modify the voltage and output to charge and maintain batteries long term.

 

[Dan in MI]

All alternators put out what the regulator tells it to. Yes if the battery SOC requires charging it will run in the 13+ range, if doesn't and the load consumption is low enough the regulator will drop the voltage to cut back on alternator load.

Cary, You read it wrong "They only operate above 12v when the battery State of Charge (SOC) requires charging or there are high loads on the engine" It still runs above 13v a high percentage of the time. It is constantly monitored and adjusted and dropped as often as possible.

Rick, ANY and every possible thing to save .001 mpg is looked at to try and meet the ever demanding CAFE requirements.

Have you seen the grill shutters now in use? Think the old diesel cardboard trick for more heat. Well now there are grill shutters to close off the airflow over the radiator. As long as there is sufficiant cooling the shutters will close to help the aero envelope around the car for MPG gains. Just another thing that is monitored and adjusted all the time you are driving. They can be any where from completely closed to wide open or anywhere in between.

 

[mohavesam]

If I'm not mistaken, all electrical demands in a conventional auto are powered by the battery (except for some internal functions of the alternator).
The battery supplies the electricity; the alternator re-charges the battery.
Monty

BINGO!work the alt/gen.

:mrgreen:

Not quite. Your vehicle's electrical demands are met by the alternator/generator (and the dissipative system, but that's for another time). The battery gets re-charged of course but only stores energy to start the motor, and then the motor provides mechanical work (via belt) to the alt/gen.
This is why your (any properly-tuned vehicle) car will continue to run perfectly with the battery disconnected. I once ran from Memphis to Ontario with no battery at all. Of course the 351W motor kept running the entire time.

 

[Acorn]

If I'm not mistaken, all electrical demands in a conventional auto are powered by the battery (except for some internal functions of the alternator).
The battery supplies the electricity; the alternator re-charges the battery.
Monty

BINGO!work the alt/gen.

:mrgreen:

Not quite. Your vehicle's electrical demands are met by the alternator/generator (and the dissipative system, but that's for another time). The battery gets re-charged of course but only stores energy to start the motor, and then the motor provides mechanical work (via belt) to the alt/gen.
This is why your (any properly-tuned vehicle) car will continue to run perfectly with the battery disconnected. I once ran from Memphis to Ontario with no battery at all. Of course the 351W motor kept running the entire time.

Many newer cars caution against the old test of "pulling off the positive cable and see if it still runs" test. It can supposedly damage the alternator and or other major components.

 

[caryc]

I've heard that also. The system must remain in tact as it was designed.

 

[Dan in MI]

Many newer cars caution against the old test of "pulling off the positive cable and see if it still runs" test. It can supposedly damage the alternator and or other major components.

It causes a power surge and since your car now has 30 or more little tiny computers running parts of it, do you want to risk a power surge cooking a module or two?


I helped diagnose a fire truck in Mexico that was hit by lightning. It fried every module on the truck but you didn't know until you replaced a module then you'd get codes module B wouldn't communicate, then you replace B and C won't communicate...... All kinds of fun over the phone.

 

[blume357]

I'm thinking lower voltage 10.5-12 on a DC motor will not harm the motor... now with that said... big difference on a AC motor.... reduced voltage will reduce the life of an AC motor.... at least this is what I've been told... power tools should use at least a 12 gage cord and as short as possible.

The one problem I've run into with automobile voltage is the Milwaukee 18 volt cordless tool battery charger I bought to use in my work van.. Needs just over 12 volts to work and so will only charge a battery if the vehicle is running.....

I thought lead acid battery cells were 1.5volts and thus you have 8 cells to a battery.... newer rechargible nicad and litheium batteries do the 1.2 volts per cell.... I've hardly ever seen a good vehicle battery that put out 12volts ... and if it does that voltage drops pretty steady with any load... with a vehicle running usually the voltage is 13.5 to 14.5 depending on load.... at least that is what my GPS shows....

 

[Rick Courtright]

I thought lead acid battery cells were 1.5volts and thus you have 8 cells to a battery.... newer rechargible nicad and litheium batteries do the 1.2 volts per cell.... I've hardly ever seen a good vehicle battery that put out 12volts ... and if it does that voltage drops pretty steady with any load... with a vehicle running usually the voltage is 13.5 to 14.5 depending on load.... at least that is what my GPS shows....

Hi,

Oops, fingers and brain disconnected in my other post, Blume! Went back and fixed it. Conventional lead acid cells run about 2.2 volts, so 6 cells x 2.2 volts/cell = 13.2 volts. Fully charged (operative term: many aren't, even in supposedly normal use), most good batteries I've checked on my own vehicles (with a voltmeter--my GPS is only smart enough to show me where I am! ) will put out as much as 12.5 volts when new, and usually still at least 12.0v after a year or more, with the engine off, headlights on high beam. Dunno how today's testers work, but years ago we used to use a "load tester" that simulated the draw of a starter. IIRC, ~10.5v during that test was considered '"good" back then, with ~9.6v or lower the "fail" point. That 13.5-14.5v running output your GPS reports has been the rule for a "dumb" generator/alternator system as long as I remember.

This newer "smart" stuff I know little about and care even less for...

Rick C