88 4Runner V6, I think the alternator is going out.

[VTISC007]

Recently I noticed that my battery light and brake light on the dash turn on and off simultaneously. Sometimes it does it every now and then and sometimes more frequently. Lately it's been more frequently. I've never seen on any car both the battery charge & e-brake indicators turn on and off at the same time only when starting the vehicle. What's a good way of trouble shooting this problem. I don't want to buy a new alternator if that's not the problem.

[Brian R.]

I don't think alternators gradually die, they just stop working. What is the problem exactly? Does something not work? Trouble starting? Battery not charging? what?

[[iV]Kermit]

I'm not trying to go against Brian R.

My alternator was bad on my 97 Ford Escort which has 87k.

I recommend going to a place like autozone and leaving your battery with them for 45 minutes so they can see if it works. They can also test your alternator after the battery is fully charged. FYI - this is free to test.

My car was doing the same thing as yours. Replacing the alternator should be easy. Good luck.

[Brian R.]

Sears is another good source of electical testing. Describe your truck's symptoms.

Unless things have changed recently, there is a big difference in quality and cost between an Escort alternator and a 4Runner alternator. Test long and hard before you pay for an alternator. My American cars periodically needed new alternators. None of my Japanese cars (Hondas and Toyotas) have ever needed an alternator.

[VTISC007]

As I watch my volt meter on the dash, it seems to go down a little whenever the brake or battery lite turn on. I don't know exactly how many volts it's reading, at the top it 18 volts and at the bottom it's 0 volts. I somehow managed to ruin a brand new Die Hard SUV 4X4 battery, it was about 7 months old. I don't know if I let the truck sit for too long, or maybe there's a short somewhere that's messing with me. I broke my leg in December so I wasn't driving it for a couple of months but I would turn it on and let it run for about 15 minutes every so often. I've had to charge the battery 3 times until I took it back under warranty. If I drive the truck daily it will start no matter what. If I let it sit for about two weeks it might not start. I have a brand new battery now so it's hard to tell. It almost seems like something is drawing too much current like as if I were running a bunch of amps and off road lights, but I'm not. The volt meter on the dash seems to fluctuate, sometimes it seems to be near 15-16 volts estimated and sometimes near 10-12 volts estimated. When the needle goes up, the battery & e-brake indicators turn off. When the needle goes down they turn on. I was thinking of getting an upgraded alternator someday but if I don't need one right now, what's the point. I'm somewhat perplexed as to why the e-brake indicator turns on along with the battery indicator, aren't they two totally differnt sensors.

[Brian R.]

The battery indicator is showing the drain (low battery voltage). I'm guessing that the other light is next to it and just picking up the light from the battery indicator bulb.

Since the battery drains when unattended, it is possible that you have an intermittent short or drain. If you can predict when this problem will occur, you might consider pulling fuses out one at a time and seeing if taking out any one circuit solves the problem. Should reoccur when that fuse is replaced if that circuit is the drain. Make sure you don't remove a fuse that's necessary for safety or driving.

"If I drive the truck daily it will start no matter what." - I guess it could be an intermittent problem with the voltage regulator. I don't understand why it would not act up if the truck is driven regularly.

Not for nothing, check that your alternator drive belt is tight and in good shape.

[pricebbp]

The double light is a real thing and my 87 did it too. Both brake and ALT light came on at EXACTLY the same time which was the tipoff they were somehow wired to do this if it was a real bad probelm (vs. just kinda low voltage or slipping belt). Since replacing alternator 3 years ago it has happened again once or twice while driving on the highway but now it "resets" immediately when I turn off ignition and then restart. Makes me wonder if mine is a real problem or some odd glitch (or perhaps a bad ground, short in voltage reg etc. - search history in discussion).

If both lights are on and they stay on, Fix it soon before the headlights dim and it dies. You'll see the ALT & Brake lwarning lights dimming too. Any ideas on why mine both come on but appears to reset after power-off & restart would be appreciated.

[VTISC007]

Not for nothin Brian, my alternator belt just snapped. I was planning to change all the belts including the timing belt soon, I guess I'm doing the job a lot sooner now. I took off the timing belt cover and sure enough that belt was looking bad too. I just ordered a bunch of parts from Toyota including a water pump, pulley, tensioner & spring, hoses, and thermostat. Why change just one belt, I like to do everything since I've got it all ripped apart. I'm also installing an electric fan since I'm there. I sure hope that a loose alternator belt was the cause of all of this. I get my parts on saturday. I'll keep you guys posted on whether or not this problem is indeed the works of a bad alternator belt.

[Brian R.]

The loose/worn alternator belt sure didn't do it's job as it should. Good luck. It is fortunate your timing belt hung in there and didn't give out at a bad time.

[VTISC007]

The job is complete.
New:All belts including timing, timing pullies, tensioners, water pump, oil seal at the crank, thermostat, radiator hoses, two heater bypass hoses that looked like they could use a break, new valve cover gaskets, egr valve, fuel injectors rebuilt and balanced, bored out the throttle body and installed an electric fan.
It feels more responsive and I definitely feel a gain in torque.
When I turned it on, my volt gauge was reading near the top, battery & brake light were off. I thought for sure the problem was the alternator belt, given the occurence.
After turnig her on and off a few times, the battery light and the brake light returned back to it's problematic self again.
I pulled the connector off of the brake fluid reservoir sensor, the lindicator lights had turned off, but the volt gauge was still fluctuating too much.
Back to the old drawing board.

[Brian R.]

Looks like the alternator is the next most likely cause. Have the alternator tested. Most likely an intermittent short to ground in the voltage regulator or related circuit. If you can predict when this will happen, try testing the fuse circuits as I described in the above posts. Maybe you can find a bad circuit external to the alternator. This intermittent drain has to be found if it is external to the alternator.

[VTISC007]

It was the alternator!
My truck finally died after a couple of days of driving with the battery/brake indicator lights on. At least she die as I pulled up to my drive way and didn't leave me stranded on the side of the freeway.
I replaced the alternator and I have had no problems.

Much better fuel economy with all the service performed!!!

[goon]

I have an 88 22re 4-runner and have the exact same issue. I will replace the alternator. Did you ever find out what in the alternator was bad? Mine goes out from time to time so I assumed it was a short or intermittent connection. Sometimes it is on when I start it and sometimes not. Very strange way to find a fault. Thx

[Brian R.]

Dollars to dohnuts it is the voltage regulator.

[VTISC007]

Yeah, I havn't check it yet, but I'm pretty sure it's the regulator. Regulators are pretty expensive, so I figured, for a few extra bucks just get a new one (Remanufactured from Toyota). If you get a rebuilt one from the auto parts store, chances are, you are going to go through a few of them until you get a good one. A good remanufactured one from Toyota was only like $30-$40 more than a cheesy one from AutoZone. I kept the core. I plan on putting a new regulator in it and getting a new brush kit also. It will be my spare.