Car stop-start system and A/C?

[Artfuldodger]

In these modern cars that stop & start the engine while one is sitting in traffic, how does the air conditioner work? Isn't it still driven by the engine? I guess there is enough cooling in the duct-work to provide a small amount of cooling before the engine would have to restart to turn the compressor again.

Also if you put the a/c controls in Max, will it keep the car running or is that just on certain models?

 

[j_seph]

not sure but in my 07 silverado I can run AC for little bit, then turn it off and use the recirculate and usually not have to turn AC on again

 

[Artfuldodger]

not sure but in my 07 silverado I can run AC for little bit, then turn it off and use the recirculate and usually not have to turn AC on again

Yeah, I can get a bit of cooling when turning off the A/C. Maybe about 15 seconds though in August. I was just wondering if a car being off for only 15 seconds would be worth shutting down the engine to save gas.

 

[NE GA Pappy]

a lot of the new cars are using an electric motor to turn the a/c pump

 

[paulito]

my 2018 f150 has it. bit of a pain in the rear if you ask me. AC compressor ddoes not run when the truck is off. If i adjust the temp or the fan speed when the truck is off it will turn back on immediately. If not it just blows recirculated air until it senses that the internal temp is rising. in the heat if the summer the truck will turn itself back on when sitting at a long light to get the AC going again. funny thing is with all the fancy on/off whatevers.......still gets about 16 MPG city. go figure.

 

[Eudora]

a lot of the new cars are using an electric motor to turn the a/c pump

And on most cars now, the power steering does too. Less strain on engine for better mpg.

 

[Artfuldodger]

And on most cars now, the power steering does too. Less strain on engine for better mpg.

I don't see how anything electrical is less of a strain on the engine. The energy shifts from a mechanical load to an electrical load. The engine then has to provide more power to turn the alternator.

 

[Artfuldodger]

a lot of the new cars are using an electric motor to turn the a/c pump

Maybe that's to let the car stay off at a traffic stop. You could sit there a minute instead of 15 seconds if it was an electric compressor. They must use an inverter or something.

Again, energy is energy, the engine would use the energy saved at the traffic light to power the alternator load which would now be more from using the battery reserve at the traffic light.

 

[Artfuldodger]

I think I read this start-stop system saves 5% on gas over a year. they must also have some rally good starters. True the engine is warm and they start back up fast.