saywatt
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Leaf Number: 4701
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Wonder how the AC and brakes work while not moving????

Thu Jul 14, 2011 5:55 pm

I wondered this after having my LEAF for less than a week. AC and Power Steering typically have pumps—AC has a compressor, and power brakes have a pump. When I turn the car on, I hear a motor so I assumed it was the drive motor at some slow idling speed to run the two pumps OR each had it own electric motor. So I asked Nissan and the answer I received was that each has its own motor but still uses the Li-Ion to run them. Just FYI

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turbo2ltr
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Re: Wonder how the AC and brakes work while not moving????

Thu Jul 14, 2011 7:36 pm

You sure lived up to your username with your first post!

The power steering and brakes are both electric and I think run off the 12V. There are no pumps.

The AC has a compressor which runs off the pack voltage. You can clearly hear it if it's on, it sounds like a refigerator. If the AC is off, the faint whirr sound you hear when not moving is the motor/inverter/charger coolant pump. You also hear it when you charge.
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saywatt
Posts: 233
Joined: Thu Jul 14, 2011 7:43 am
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Leaf Number: 4701
Location: Issaquah, WA

Re: Wonder how the AC and brakes work while not moving????

Thu Jul 14, 2011 8:43 pm

Correction—I meant the power steering, not brakes. And an AC compressor is a pump, in a way. As I said, but perhaps not clear as to who said it, it was a Certified Nissan LEAF technician (you know, the guys who are going to be working on our cars) who said the AC and power steering have their own motors and use the drive battery for their power. Who am I to disagree with "Scotty"? :)

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turbo2ltr
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Re: Wonder how the AC and brakes work while not moving????

Fri Jul 15, 2011 4:09 pm

Trust me when I say the $20 service manual knows more than the Certified Nissan Techs. It's not the first time they have told people wrong info...and it won't be the last.

Page STC-14 of the service manual clearly shows the electric PS motor (it's not a pump, it's a servo applying force directly to the steering shaft, there is no fluid involved) powered by 12V.

As I agreed, the A/C compressor does run off the high voltage. So they were only partially wrong.

Read my other posts, I'm not someone that would say something I'm not 100% sure of.

Now Beam me up!
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garygid
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Re: Wonder how the AC and brakes work while not moving????

Fri Jul 15, 2011 4:30 pm

Darn, caught in the Pattern Buffer again ... another century gone by! :lol:
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EVDRIVER
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Re: Wonder how the AC and brakes work while not moving????

Fri Jul 15, 2011 5:13 pm

turbo2ltr wrote:Trust me when I say the $20 service manual knows more than the Certified Nissan Techs. It's not the first time they have told people wrong info...and it won't be the last.

Page STC-14 of the service manual clearly shows the electric PS motor (it's not a pump, it's a servo applying force directly to the steering shaft, there is no fluid involved) powered by 12V.

As I agreed, the A/C compressor does run off the high voltage. So they were only partially wrong.

Read my other posts, I'm not someone that would say something I'm not 100% sure of.

Now Beam me up!



Same as so many other cars. Nissan techs can be anywhere form clueless to very well informed but few are EV or electrical expects. They may be able to rebuild a part (not done much now) but they sure have no idea how to repair an inverter. It's scary having to coach the Nissan techs and service people on whats wrong with the car and how things work. I'm sure in time this will change a bit.

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Re: Wonder how the AC and brakes work while not moving????

Fri Jul 15, 2011 5:19 pm

Luckily other Nissan cars use the same power steering systems, so they will know how to fix it.. motors, inverters and batteries will just be a swap with factory rebuilt parts and hopefully no one gets electrocuted in the process.

drmanny3
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Re: Wonder how the AC and brakes work while not moving????

Fri Jul 15, 2011 5:33 pm

"The power steering and brakes are both electric and I think run off the 12V. There are no pumps".

Yes they have a electronic component due to the regeneration process. However they are standard hydraulic brakes. The brake system uses brake fluid and essentially is a mechanical system. What makes it unique is that electronically the system determines what is happening (how fast you are applying the brakes, how much pressure you are applying, etcetera) it then decides how much regeneration will take place and how much actual braking (using the disk brake pads) will occur. It is a really cool system. Lots of failsafe’s built in.
Manny

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aqn
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Re: Wonder how the AC and brakes work while not moving????

Fri Jul 15, 2011 8:34 pm

The brakes are assisted by a hydraulic pump:
Image

From the Nissan Service Manual, page BR-11:
Contains a motor and generates boost force according to the amount that the brake pedal is depressed and the amount of cooperative regenerative brake control.
Uses the boost force to generate fluid pressure in the master cylinder.

The pump generates hydraulic pressure which then acts directly on the master cylinder's piston.

This differs from ICE cars where intake manifold vacuum is used to "power" the "brake booster" which in turn supplies mechanical force on the input shaft of the brake master cylinder's piston.
Anna Nguyen

saywatt
Posts: 233
Joined: Thu Jul 14, 2011 7:43 am
Delivery Date: 25 Jun 2011
Leaf Number: 4701
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Re: Wonder how the AC and brakes work while not moving????

Fri Jul 15, 2011 11:01 pm

OK, so if we strip off all the semantics:

The brakes, which I mistakenly included in the original post, use a hydraulic pump with a kind of motor component.

The power steering uses a servo, a kind of a motor,

The AC uses a compressor, which includes a kind of a motor.

So, I'll give the LEAF tech better than 50% right/wrong. He was probably just stating the answer to my question in layman's terms.......kind of how I did above.

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