Slightly notchier/rougher shifting with AC on

['23WhiteSi]

Hi All,

I bought my ‘23 Si earlier this year and have been loving it so far with just over 4,000 miles. I really have no complaints other than the fact that I’ve noticed for awhile now that it’s ever so slightly harder to engage first gear as well as the rest of the gears (but to a little bit of a lesser extent) with the AC on. I’ve confirmed this over numerous drives where I've tested back to to back, from a stop, having the AC on and not on while putting the car into first. I’ve also driven the car for extended period of time both ways and have noticed this slightly notchier/rougher shifting that I'm experiencing. Additionally, at parking lot/crawling speeds, there is a noticeable shudder from the clutch pedal (only with the AC on) that occurs if the clutch is engaged quickly. Think if you're about to pull out onto a main road and realize you can't quite make it and quickly reengage the clutch to come to a stop. With all this being said, I know the revs drop faster with the AC on… that is not really what I'm referring to and I've adjusted my shifting style with the AC on to accommodate this, so I know it’s not related to that. Has anyone noticed this? If not, could someone please be kind enough to test this out and get back to me? The only thing I can think of is that my crazy ex girlfriend who I was dating a couple months back once kicked underneath the glove box really hard during one of her freak outs…. I’m not sure what AC components are under there and if she did damage any of them, how that could affect/influence the symptoms I’m having. Hopefully that’s not the cause. Also I hope I haven’t damaged anything turning on/off the AC so many times during my testing . Let me know what y’all think and sorry for being longwinded.

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[TypeRD]

There’s no technical reason running AC could make your shifter more notchy. The engine turns the AC compressor pulley when the AC is on. This is why your revs will drop a little faster. Running AC puts an additional load on the engine. This should have no effect on the shifter itself.

And no, there are zero AC components that would be kick-able inside the car except for the vents and the controls console.

 

['23WhiteSi]

There’s no technical reason running AC could make your shifter more notchy. The engine turns the AC compressor pulley when the AC is on. This is why your revs will drop a little faster. Running AC puts an additional load on the engine. This should have no effect on the shifter itself.

And no, there are zero AC components that would be kick-able inside the car except for the vents and the controls console.

would you mind testing it though for me? i get that it kind of seems ridiculous but for instance today i tested it, at a dead stop turning the ac on, slotting it into first and then turning the ac off and slotting into first. tried shifting each test multiple times and duplicated like 3-4 smooth rougher shifts in a row with the ac on and the same amount of smoother shifts with the ac off. and about my girl kicking the section underneath the glove box, it may seem funny to you but it’s not to me. i spent over 35k on this car as a young kid and it makes me really anxious thinking of her potentially messing something up like that. she kicked hard and multiple times. i’ve also heard that there’s the blower fan located in that section, not sure if there’s any other components.

 

[TypeRD]

I don’t have an Si to test this, but the FL5 has the same shifter as the Si (from my understanding). AC and ventilation system is most likely the same too.

I don’t know man. I’ve driven manual vehicles for the last ~20 years straight. The AC has never affected the shifter in any car (or truck) and I don’t see how it is technically even possible. Are you certain this isn’t a weird case of confirmation bias? Honda shifters can be a little notchy in general, though my FL5’s shifter has been smooth and precise almost always. I recommend changing your manual trans fluid to Amsoil. It’s GREAT and can alleviate most if not all shifter notchiness, in my experience. I think this all could simply be a weird coincidence that you’re experiencing the notchiness when the AC is on.

It’s not funny that she kicked your car. I’d be pissed too. I’m laughing because I VERY highly doubt she messed up any of the ventilation components. She would have had to basically destroy your dashboard to even reach the fans back inside there!

 

[Chilly613]

There is a metal frame around the glove box and the plastic would probably break or deform before the metal. If there was an issue with the AC you'd probably notice it or hear something as the the blower sits well behind all of that. Sounds more like it may be an issue with your transmission. AC wouldn't make it notchy, it would put an additional load on your engine, but should have no affect on you changing gears. If you're having issues getting into gear, it may be a clutch/transmission issue, the shifter cables could be binding or bent. You're under warranty, I'd say take it in and see what Honda says.

 

[optronix]

Interesting thread title, enough for me to jump up in here with a useless comment.

All kidding aside, there are literally no shared components between the AC system and the shifter mechanism. Barring some catastrophic damage that would be highly noticeable under any conditions, the only possible explanation is having AC on may exacerbate rev hang, which could reasonably lead to the perception of rougher shifts.

 

[heavyD]

This is not a new phenomena with small engines. Just google something like; "can air conditioning make manual shifter more rough" and you will see owners of cars with small displacement engines asking the same question.

This is common on small engines like the 1.5l because of increase parasitic load on the engine from the AC compressor causes the RPM's to drop faster. This can make shifting feel slightly different vs the AC compressor off.

 

[Cbau]

I remember reading your long post about your ex girlfriend. Glad you broke up with her. Lol.

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