Alternator light coming on intermittently (1 Viewer)

[dparnas]

In my 97 LC, recently, I noticed the alternator light had come on, periodically, but eventually seemed to go away and volt output gauge, when the light was on, was showing under half output and then when the light went out, it jumped to above half output. The car has been working fine, but obviously don't want to get stranded. Just would seem that if the alternator had gone bad, it wouldn't be intermittent. Perhaps it is on its way out, but just hasn't completely given up yet. Anyone experienced this before? Wondering if it could be something else electronic or if there's just a good way to better diagnose the problem. How big of a job is it to replace the alternator?

 

[jpoole]

Could be that the brushes are worn out and not always making good connection. I assume it could also be a weak connection elsewhere in the charging circuit. Both of these are relatively easy to check and the brushes are pretty inexpensive to buy/replace should they be worn out.

27370-75060

 

[alia176]

If I were you, i'd take your rig to an auto parts store then have them check out your charging system. They can hook up to your car and help you diagnose it further.

if you have the original alternator, you can rebuild it. It all depends if you're comfortable with this degree of tinkering, but Toyota sells the brushes and the bearing. From memory, I moved the PS reservoir out of the way, and removed the oil filter. Doing these two things makes it easier to extract the alternator out. I'd say 45min or less for the first timer.

In my 97 LC, recently, I noticed the alternator light had come on, periodically, but eventually seemed to go away and volt output gauge, when the light was on, was showing under half output and then when the light went out, it jumped to above half output. The car has been working fine, but obviously don't want to get stranded. Just would seem that if the alternator had gone bad, it wouldn't be intermittent. Perhaps it is on its way out, but just hasn't completely given up yet. Anyone experienced this before? Wondering if it could be something else electronic or if there's just a good way to better diagnose the problem. How big of a job is it to replace the alternator?

 

[landtank]

Likely the brush assembly. They last a really long time but not forever. I change them out on all my Toyotas as part of baselining a new vehicle.

 

[ERG80]

I had a similar issue a long time ago. Mine was from mud caked in the alternator. Have you been in any mud lately?

 

[Kernal]

All the above, maybe check the basics also, any noise from your alternator belts, screech when you start the engine or accelerate? Are the belts loose??? Are the connections good on the battery posts? Is the harness connector going into the alternator snug??

FWIW, had a loose connector at the alternator once, caused the Red light to come on.

Replacing the alternator is not super difficult but there are a few tips and tricks. You need to remove the battery and battery tray to get better access, remove the bolts holding the PS reservoir to the intake, push it rearwards, then once all the bolts and wires are disconnected pull the alternator up and out rearward working from the left side leaning over the fender.

If the alternator is aftermarket might be better long term to replace it with a Toyota-Denso reman from Toyota, or new Denso alternator (RockAuto).

Here's a couple of videos.

Replacing the brush assembly:

Toyota Alternator Brush Replacement

OTRAMM is an independent Toyota, Lexus, and Subaru repair shop in Bealeton Virginia. Contact us today for your repair, maintenance, and modification needs. ...

www.youtube.com

This is good if you speak Australian:



Silent and fast overview:

 

[LongDuck]

As its only the back cover that comes off to replace the brushes, has anyone attempted this IN the truck, thus saving removal and retensioning?

 

[Kernal]

Thought about it but IMO someone would have to be about 16 years old (no pains in joints, back, neck, shoulders--), double-jointed (super flexible), 110 lb (so you could breath while your gut is pressed against the fender), perfect near and far vision, perfect dexterity so you don't drop the small screws, magnetic tipped tools, and ~6'4" tall (so you have the reach) in order to work down in that area with the alternator still in place.

Or, an under 4' small person might do it, someone who could squeeze down into the engine bay head first while the taller guy holds him up by his ankles (think Mad Max, Fury Road).

Taking the alternator off to service it gives you the ability to check the slip rings that the brushes wipe on, those can get worn and develop a build-up of old brush material. I take something like a 3M pad or 800-1000 grit sand paper to lightly clean up those copper ring (you don't want to remove much metal), then clean it off with Contact cleaner. Also you can get a better idea IME of how the bearings feel by spinning the pulley.

The job is not that bad and you can take care of a bunch of other PM's while it's apart: clean and check for leaks (timing cover, power steering pump, hoses), replace hoses, belts, pulleys, fan clutch, oil pump cover gasket, remove rust and paint under the battery box. I always find a little rust trying to get a foothold under there, partly from battery acid vapors, partly because water get trapped), the box itself can wear down/scuff the paint to bare metal.

Example, after sanding, priming and painting to protect the metal under the battery box while it's out you can (I did) glue small thin solid rubber pads (cut from a sheet of rubber) to the sheet metal where the box scuffs through the paint. A little OCD but you won't have to worry about rust in that area for a very long time.

FWIW

 

[mudgudgeon]

This is good if you speak Strayan:

Fixt!

 

[12bit]

This may not help at all, but I had a similar symptom I was chasing on a 3rd gen 4r. Battery light would intermittently come on. It would occasionally leave me with a dead battery. It ended up being the wiring under the alternator fuse. The nuts had come loose and the wiring was vibrating randomly. It was the easiest fix that took me far too long to find.

 

[REKCUT]

First, before you start following guesses based on past peoples experiences, you need to get a real reading on what the alt is doing. The gauge on the dash is a dummy gauge and not of much use. I would suggest you get an ODB reader and then you can get real numbers as to what you alt is doing. Find out if the voltage is dropping and when. Then and only then would I start working towards a solution.

 

[BILT4ME]

My alternator light would come on occasionally and I would watch my voltage on my UltraGauge. Voltage would drop way down, I would rev up the engine past 3500 RPM and it would re-excite and work for a while. This happened three times in a 3-1/2 hour drive.

Since it's my DD, I called my local dealer and they had one in stock, so I picked it up and installed it. Took me about an hour to install and half that time was digging out the right tools.

That's why I have my UltraGauge so I can watch voltages and O2 sensor info to be ahead of problems.

 

[Kernal]

I know sheit about how electrons work, but FWIW if anyone missed it, the Aussie video in the link above goes over some of the most common causes of the Red light of death, IME.