Is it common to have your headlights dim and your fan rpm dip when the ac compressor comes on (defrost mode) in a 2013 Fit? I have no lights on in the dash to show a problem. I've replaced the battery. Any ideas?

 

Yep, normal. My 07 Pilot does the same thing.

 

Maybe LED headlights will help? Less current draw.

 

Normal, but only noticible at idle. Get any kind of load on the engine and when the fan kicks on and off it's indistinguishable.

 

Very normal. Just ignore.

 

I see it all of the time ('11 Sport AT).

 

I was actually just thinking about creating a similar thread because I thought there was a poor ground somewhere.

My headlights dim when the fan kicks on too. It not only happens at idle but at low speeds when the car is moving — which could be somewhat distracting to oncoming traffic. So not only is it annoying (actually it’s super annoying considering how often the fan kicks on) it’s also potentially dangerous.

My Fit is a 2013 base.

 

It is the ac load. You can see the same thing if you turn the wheel (electric power steering starts drawing current)

 

That could help.

Upgraded alternator might help also.

 

As noted in other threads on battery upgrades, the FIT, as is everything really, is designed to do 'well enough' for 'most owners' in 'typical environments'. For example, I wouldn't think a FIT's heating system would do that well north of the Arctic Circle (~66.5 degs north lat). I know that the A/C is marginal even in Pennsylvania (40 degs north lat) on a hot muggy day let alone in the Tropics (+/- Equator).

So, the whole electric system is on that 'knife edge' that was designed to be 'good enough' for the intended FIT market and when the big draws occur: A/C kicks on or steering input is required or your big-ass sound system drives the bass speaker, you'll most notice that intermittent draw in the lights since their lumens & color output is sensitive and your eyes easily pick up on those changes. I'm sure other systems in the FIT drop in performance at the same time but you really only notice the headlights. As long as these 'spikes' are very short, the existing 'light weight' wiring / alternator / battery can handle them. LED lights 'might' help but may not if the change in amps / watts only addresses 10% of the overall system load.

As GolNat said, you could increase alternator output, plus add a bigger battery, plus add heavier wires, plus ....... These little FIT headlight flickers is the 'nature of the beast, as they say and don't represent a pending failure. I'm sure there are exceptions but you should see alarm lights going off on the dash if alternator failing, etc.