Turning off all accessories when starting car

[mclasser]

When I first learned how to drive, I was told to make sure things like the HVAC system, headlights and radio were off before starting up the car as to reduce excess load on the engine and electrical system. I'm not sure if there's any actual proof this does anything but it's a habit that's stuck with me til this day.

I believe the logic stems from the idea that starting the car, for example, with the AC blasting puts an increased load on the compressor. Similarly, starting the car with the headlights on puts an increased load on the battery, alternator and on the bulbs themselves. This is just my simplistic thinking; in no way am I an expert on the intricacies of automobiles. People who are knowledgeable on the subject, please chime in and correct me.

 

[Chris142]

Those things are computer controlled on most cars made in the last 20 years.the computer wont turn them on until its ready to do so.

 

[Nick1994]

I don't turn them off but when they are on and I start my car the A/C compressor makes a weird rumbling noise. If I start it with the A/C off it doesn't make the noise.

I still leave it on 99% of the time lol.

 

[old1]

I always thought (back in the old days) that the reason was to keep the most battery voltage available for the ignition.

 

[splinter]

I learned the same starting procedure.

All my modern cars/trucks cut the juice to most accessories (e.g., fan, windows, wipers, etc.) when in the 'crank' position.
I'll still switch off the DRLs/headlamps manually, though.

Perhaps I'm worried about being stranded on a harsh So Cal winter morning.

 

[GiveMeAVowel]

Originally Posted By: Chris142
Those things are computer controlled on most cars made in the last 20 years.the computer wont turn them on until its ready to do so.


This is correct. Even if you have things like the A/C selected the system and compressor will not activate until the car is already running.

 

[HTSS_TR]

My old habit: turn off everything when I park the car, turn on what are needed after engine started.

 

[oldhp]

The ECU monitors everything now, like if you hold the key in the start position a tad long after engine starts.....no starter engagement.

 

[Brybo86]

Originally Posted By: HTSS_TR
My old habit: turn off everything when I park the car, turn on what are needed after engine started.


^ This as well, wife thinks I'm crazy but hopefully some of it is rubbing off on her...

 

[tinmanSC]

Originally Posted By: Brybo86
Originally Posted By: HTSS_TR
My old habit: turn off everything when I park the car, turn on what are needed after engine started.


^ This as well, wife thinks I'm crazy but hopefully some of it is rubbing off on her...

Why? In modern cars it probably makes no difference. What benefit is turning off the AC in a car where the computer turns off the AC before the engine is started anyway?

 

[bubbatime]

That's a lot of wear and tear on switches by turning them off and on every time you turn the car off/on. My mother in law does it and I asked her why. She didn't know, just said that is what she has always done. It is completely unnecessary on a modern car. In my car AC is on full blast, radio on, cell phone charger plugged in. Car doesn't know the difference.

 

[901Memphis]

I always turn the radio off a minute before I stop and turn the AC to vent too

 

[Gasbuggy]

Originally Posted By: bubbatime
That's a lot of wear and tear on switches by turning them off and on every time you turn the car off/on. My mother in law does it and I asked her why. She didn't know, just said that is what she has always done. It is completely unnecessary on a modern car. In my car AC is on full blast, radio on, cell phone charger plugged in. Car doesn't know the difference.


Yep, I actually broke my girlfriend of this "bad" habit. At 75,000 miles all the knobs for her hvac were loose, one came off not long after. She also was taught another bad habit, giving the engine a light rev right before shutting it off.

 

[CharBaby]

Originally Posted By: old1
I always thought (back in the old days) that the reason was to keep the most battery voltage available for the ignition.


Correct! ^^^ But today, it's this way as Chris142 mentions below!

Originally Posted By: Chris142
Those things are computer controlled on most cars made in the last 20 years.the computer wont turn them on until its ready to do so.

 

[Olas]

To save the battery from too much abuse I turn everything off when I park.

When I get back in the car and start it, everything is already off so I can just switch stuff on if and when I need to.

 

[Rick in PA]

Originally Posted By: Brybo86
Originally Posted By: HTSS_TR
My old habit: turn off everything when I park the car, turn on what are needed after engine started.


^ This as well, wife thinks I'm crazy but hopefully some of it is rubbing off on her...


What? Your crazy is rubbing off on her?

Yeah, shut it all off before you turn the car off.

It annoys me when I hop in my wife's car and the AC starts blowing in my face as soon as I turn the key. It's really annoying when the wipers are up (obviously left on) and it iced overnight in the winter.

 

[eljefino]

Originally Posted By: tinmanSC

Why? In modern cars it probably makes no difference. What benefit is turning off the AC in a car where the computer turns off the AC before the engine is started anyway?


I had heard an "afterblow" is good for getting condensation, and resultant mold, out of the system.

I've seen volvos mute the headlights (but not parking lights) when cranking. I would be surprised by this if I stalled and had to flick it in neutral when rolling to restart.

When I installed a remote starter the wiring diagrams showed my ignition "on" had two feeds, what was needed to run, and the fun stuff, basically the HVAC blower.

 

[TFB1]

With the modern PMGR starters that draw maybe 2/3 the current of the older field types, even if everything were on, there is less current draw than with a starter of old...

I used to be big on turning stuff off(as mentioned most items are now PCM controlled), but haven't done so in years... Never had a issue cranking...

 

[Pop_Rivit]

Originally Posted By: HTSS_TR
My old habit: turn off everything when I park the car, turn on what are needed after engine started.


Agreed. I've done this since I was a kid driving on the farm and continue to do it today.

Originally Posted By: bubbatime
That's a lot of wear and tear on switches by turning them off and on every time you turn the car off/on.


The only vehicle on which I've ever had to replace a switch was a 1958 IH pickup. Other than that all of my vehicles have been able to withstand all that "wear and tear".

 

[Andrew1972]

I was never taught this and in 25 years driving had no effect on my vehicles kept into elderly years.

Does not help or hurt a thing.