I'm a new hybrid owner and new to this site, so I apologize if this topic has been discussed already ad nauseam (I did try to search for it first). Anyways, I have an 09 and my wife and I love it so far. We just made the trip from Northern Virginia to Michigan for the holiday. About 250 miles into the return trip, we hit some heavy stop and go traffic for roughly 3 hours on the interstate. During the entirety of the stop and go drive, the autostop feature did not engage once. The driving conditions were as follows:

35 to 40 degrees (F)
rain off and on
defrost on low (due to the moisture buildup from the weather)
battery level between 4 bars and full (never noticed it below 4)

I ran across one post which suggested that when the defrost is on, the autostop will not engage, but it was on an 06. Is this true of all HCH II's? If so, does anybody have any idea as to why? Does the defroster require a large amount of energy to operate? Finally, are there temperatures too hot or too cold for the autostop to engage?

Any input you can offer would put this Newbie's mind at ease (at least on this issue). Thanks in advance!

 

The defroster uses the air conditioner, which is why AS generally won't engage when it's turned on. Also, in stop-and-go traffic, you may not have been accelerating past 9mph, the point at which AS will re-engage once you slow down below 7mph again.

 

Ah, that would explain it then. So are there no situations where autostop will engage with either the AC or defroster on?

Sorry, I didn't mention that I was at a complete stop at least a dozen or so times so I was below 7mph.

Thanks for the input!

 

AS will sometimes engage with the a/c or defroster on, but it's pretty rare, and really chews through the battery quickly. The trick to getting it to function in a traffic jam is that you have to speed up faster than 9mph. If you stop, speed up to 7, stop, creep to 4, stop, speed to 6... but never get past 9, AS won't engage.

 

I don't understand the defrost thing. The A/C can run fine on autostop so why does it stop autostopping with the defrost on--even when A/C is set to off?! (that's a rhetorical question). Our Mariner behaves the same way, although it doesn't have a separate electric power for the A/C.

Personally, I turn my defrost off whenever I'm nearing a stoplight which is annoying...

 

I've wondered the same thing myself. There's probably a reason for it somewhere, or it could be another of those "doh!" things like when you pull in the garage, the car goes AS, and then restarts as you pass through reverse and park.

 

I set my climate control on auto and it works great! Normally A.S as long as the ice is warm and over 7 mph. H

 

Here is something I have tried and find it works if it is not too humid, turn on the climate control, hit the a/c button to turn off the a/c, hit the mode button (once for me) till you get a floor & defrost icon, you now have a defroster and auto stop. It is only the windshild defrost BUTTON that overrides autostop, in the mode setting all works normaly.

 

A couple more things that will prevent autostop:

1. Having the transmission in "S".

2. Coming to a very sudden stop.

If AutoStop is not happening, there's usually a reason. It may be overkill, the parameters have to be conservative enough for all situations.

Consider item 2 above: While it likely doesn't apply in your case, the logic is if you came to a sudden stop, it might be due to an emergency situation, and you might need to start moving again immediately. AutoStop could cause a slight but dangerous delay.

I also find AutoStop packs it in stop-and-go traffic. It's likely by design, to prevent excessive discharge of the IMA battery.

 

Front windshield defrost, with its dedicated button on climate control, pumps out dry, hot air with the blower on high. That's for serious Winter conditions. It is a high-drain feature.

Auto stop is also defeated by turning the blower to high.