Hey all, the battery and brake lights on my s2000 have recently started coming on together intermittently, normally while coasting. I've read that this is likely the result of the alternator beginning to go bad. Wondering if anyone here has any recommendations as to what replacement alternator to go with. There are several Denso alternators for sale between 150 and 200 bucks, and Honda OEM remans are around $400. Not sure if there is any meaningful difference between the two to justify paying double. Thoughts?

 

Further diagnosis recommended. To confirm alternator.

What is the voltage at battery before you start engine?

What is the battery voltage with engine running (at idle)?

Does the car seem to struggle when starting, like if it had low battery?

Typically, when both these dash lights come on together, the alternator is implicated for not providing sufficient charge. So there is a low voltage situation.

There are all manor of downstream effects of this. Battery will get run down, meaning engine will struggle or not start at all once shut off. In order for this low voltage scenario to even occur implies battery has already been run down, further implying this difficult to start scenario.

Once voltage gets low, all sorts of weirdity begins. Radio might act strange. Headlights might not work, blinkers blink inconsistently. Engine starts running badly.

This might even all just be a blown fuse. Did you check alternator fuses?

 

Hi,
Usually when brake/batt dash warning lights go intermittently or steady could be a symptom of an alternator going bad.
As Car Analogy stated, you should perform some basic tests to check if alternator is working correctly. Some auto parts can offer some free diagnosis, (I always think they will say it's bad to sell stuff to you tho)

if your dash cluster, specially the rev counter faintly blinks intermittently, the alternator rectifier is gone bad.
If you are going to leave your alternator as core ask if you can keep the alternator pulley. Apparently,Honda does not sell it separately anymore.

 

Voltage range across battery terminal for 1.) good battery (engine off). 2.) good alternator (engine idling).

 

...and if issue is alternator, its not difficult to replace most of the components that can go bad. Rectifier, regulator, brushes.

Only other things that can go bad electronically are the windings (overheat can melt the insulation, shorting them out). Never heard oof that happening on our cars.

Only other thing that can go bad mechanically are bearings, which can be replaced, but again, never heard of them going bad on our cars. Even with crazy high miles.

https://www.s2ki.com/forums/s2000-un...ement-1171989/

 

Since Honda doesn't make alternators it's most likely made by Denso so paying extra for an "OEM" Honda sticker on the bag doesn't seem cost effective. If it actually needs an alternator -- don't just fire the parts cannon -- a remanufactured unit is easy to find.

Alternator repair shops are everywhere. And not that expensive assuming you take the unit off yourself and just drop it off. Call them and compare their price to just buying a remanufactured unit.

-- Chuck

 

A locally rebuilt anything by a man in shed type shop is 1000x better than any parts store rebuild. If there is a guy locally that rebuilds anything you have that is worn out, bring it there.

Local guy will use quality parts and his rep rides on his craftsmanship. Parts store rebuild is just trying to be done as cheaply as possible and maximize profits.

So if there is a shop locally that rebuilds alternators, every reason to take it there. But diy, per youtube, still a very viable option.

 

Battery voltage is fine with the engine off, unfortunately I’m in the middle of another repair and can’t start the engine at the moment to test voltage at idle.

I haven’t noticed any flickering lights on the dash. The car starts okay but seems to struggle a little more than it should given it’s a new battery. I also almost always have the car on a battery tender when parked in my garage which might be mitigating the issue to some degree.

Based on the other replies here, I’ll probably test the voltage at idle when possible and then look at my options for rebuilding the alternator. I’m tempted to just DIY it, as I can’t seem to find an alternator rebuild shop near me.

 

Yes, be sure to test the voltage with the car while it is at idle. It may not be the alternator. It might be the starter.

I just helped my son replace the starter on his 2014 CR-V. It's not an uncommon thing with these newer 2010+ Hondas. If you can afford to have a mechanic replace the starter, do it. It's a huge PITA (at least on FWD cars).

 

Funny, I replaced the starter on my daughter's 2006 Acura a few years ago and it was pretty straight forward with decent access. Not a big deal and worked great. Guess making it difficult was the design challenge for Honda/Accura!