whitetaco02

Why would my RPM's drop a bit when i turn my lights on? Could it mean my alternator is going bad? I idle around 750 rpm's and when I turn my lights on it drops to around 650 or so. Turn them off and it goes back up. Is this normal?

I have an 88 4runner 22re auto by the way. Thanks

tacoma728

Mine does the same thing. I suppose it puts strain on the alternator or what not. Could be anything.

whitetaco02

I was wanting to put some PIAA 100W lights up front for offroading but I could only imagine what that would do. Anybody else??????

Tacoclimber

I know that when I have my Hella 500's, my headlights, and my rear lights on, you can definitely rear the load on the alt. I'm seriously thinking about an aux. battery...

midiwall

Yeup, very common phenomena with the stock alternator. You should also be able to see the lights come up in brightness when you rev the engine up above 1800rpm, that's another indication of a lot of load on the alt.

Most alternators have two stages - they generate a lesser amount of current at low RPM ("idle") then kick up to a higher current rating at speed. You can get around this a couple of different ways:

- Replace the alternator pulley with a smaller one. This will allow the alternator to spin faster at lower RPMs which, if it's spinning fast enough, will generate more current.

- Replace the alternator with a higher capacity one. The alternator will (more than likely) still be two stage, but the lesser stage will be greater than what you have now.


Putting more load on the alt isn't a swell idea. "Some" lamps is vague, but if you're talking about 2, then that's 200w of additional load, or about 15 1/2 amps. I think your stock alternator is rated at 60amps, so you're looking to add 25% more load to it.

I'd start looking for a larger alternator... Search on the forum and you'll find a lot of options. Be warned though, they're EXPENSIVE.

whitetaco02

man, thanks for the reply and that was very informative. I was wanting to put two on there but will wait for the right time(new alternator). Do you have a part number or a link of what might work for me? thanks

midiwall

There are a few threads around here talking about alternators. You'll kinda' need to search and read through 'em a bit and look at what people are saying about the options. Here's a couple of starter links:

https://www.yotatech.com/forums/f116/stronger-alternator-100839/
https://www.yotatech.com/forums/f116/alternator-problem-h-o-advise-101144/

Many Moons Ago a lot of folks (myself included) headed to Mr. Alternator, then there seemed to be a run of really bad experiences and people stopped heading to him. Most folks are now pointing at Mean Green... I dunno much about them.

There are other alternatives - a Toyota MR2 comes stock with a 100amp alternator and folks have done up brackets to get them to mount up. GM makes some beefy alternators, again with the right brackets you'd be good to go. There's the route of a custom wind on a stock alt, but by the time that's done (given the down time or having bought a used stock alt to do the wind on) then you're probably better off having bought a High Output ("HO") in the first place.


Tacoclimber mentioned dual batteries... That'll certainly help pick up the load while you're sitting idle, but remember that you need to come up with a way to keep BOTH batteries charged. Here's some reading about all that fun:

https://www.yotatech.com/forums/f31/dual-battery-installation-faq-55894/
(that link in the first post is dead, but the thread has good info in it)

BigBluePile

iTrader: (3)

http://www.4x4wire.com/toyota/tech/alternator/

This is what I did, works pretty well and was pretty simple to do. Plus it was way cheaper than buying a whole new hi output altenator. If I was to do this again, I'd get an altenator out of a junkyard and mod it. Becareful though, because you start this mod, there's no turning back! I had it checked with a load machine at an autoshop and I was way better over stock.

misterzee

The bottom line here is that it takes power to make power. Same as with any accessory on the engine. There are VSVs that kick up your idle when the A/C comes on, etc. The 22re is probably not generating too many HP when its idling... So, load the alternator, and the alternator will load your engine.

BigBluePile

iTrader: (3)

I thought about doing this as well, but I was too paranoid about burning the altenator up faster over time. Dual batteries is a good choice as well, but lots of cash depending on how you do it. You could always put a hand throttle in to bring up the RPM's when needed to run up lights or a winch. Start small and go from there.

whitetaco02

thanks man, I appreciate the info and the links. I have done some reading about Mr. Alternator and the GM ones but not sure if I want to go that route from what I have read. I will do some research first and a lot of searching on here as well. Thanks!!

whitetaco02

Thanks man, I may look into that. Good reading material!!

L33T35T 4Runner

The whole alternator thing is very true. another theory i have, although i'm not 100% sure is your coil wire. if you are running say 13.5 volts through your coil wire for your spark plugs then you turn your lights on, your volage might drop to 13, therefore giving your spark plugs less power and a colder spark,

I could be full of crap, i dunno, it's just an idea

midiwall

Remember though that the plugs see the result of that low voltage DC going through a coil to kick things up a magnitude or twelve. The 1/2vdc drop at the input of the coil _will_ make a difference, but in the grand scheme of things you're talking about 3.5% or so. It "shouldn't" make a major difference.

OSU4Runner

Does anyone know where to get a smaller alernator pulley for a 2000 4runner 3.4? I have the same problem....especially when I turn my hellas on. I don't want to spend the money on a HO alternator. How hard is the dual battery set up to do?

Matt

crackerjack

MY trk pulls down when the electric fan kicks on .
^LC Eng. has pulleys