Alternator Issue? A/T Oil temp, E-Brake, Battery Voltage light all come on at idle. (1 Viewer)

Joined
Dec 30, 2019
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Hello,

This is my first post on MUD, so bear with me here...

Vehicle: 1992 FJ80 with 205,XXX miles.

The truck drives great, just had new radiator put in two weeks ago, and I have been slowly replacing all of the necessary PM parts over the last 6 months. I am the second owner of the rig. It is unmolested, and only have done radiator, PM, brakes, etc.. nothing crazy.

On my drive home last night, I noticed the "Christmas Tree Light Effect" of all three A/T Oil temp, E-Brake, Battery Voltage lights coming on at the same time (signifying an alternator about to go?) The voltage looks OK, so that is why I am a little confused. I took a peek at all battery connections, and noticed the positive terminal was wayyy past due (corroded and cracked), so I replaced that this morning with a brand new shiny one. No luck and the lights still come on at idle. Lights only come on at idle. When engine is revved, lights go away and then come back on at rest.

After looking at the 12V 80 Amp alternator itself, it looks pretty new and clean with a sticker date of 5/14/2016 on it. All connections are solid. The battery itself is new (replaced 5-6 months ago)

I noticed the battery fuseable link wires look to be on their way out (guessing they are the originals on there) so I just placed an order for a new one and will be replacing that in the next few days. Could that have anything to do with the lights coming on, or not supplying ample power?

Any advice here would be greatly appreciated!

Cheers!

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Joined
Dec 8, 2006
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New Jersey
Those dash lamps indicate a fault in the charging circuit (alternator/battery/cables)
First thing to check is battery terminals and associated wiring.
Measure the voltage across the battery terminals with the engine running, and you'll have your answer.
 
Joined
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Utah Valley
I will add that I had a broken charge lamp relay get in the way of these exact lights lighting up when they should have, so go poke at yours with the key on and confirm it doesn't buzz/click when you do. It's in the underhood fuse box.
 
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Mine all came on one day, the smoke from my alternator was a good clue to the problem. Replaced it and I everything was good. Also check the wiring at the alternator plug, I once had a jiffy lube break off two of the 3 wires coming out of the alternator. Put a big hiccup in a trip my family was on.
 
Joined
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Those dash lamps indicate a fault in the charging circuit (alternator/battery/cables)
First thing to check is battery terminals and associated wiring.
Measure the voltage across the battery terminals with the engine running, and you'll have your answer.

Hey jonheld, thanks for the response here, greatly appreciated. Went down to the store today and bought a multimeter. I tested it on my other car to make sure readings were accurate. Here is what I got from the FJ80

-Engine off- Battery reads 12.37v
-Engine running- Battery reads 12.55v
-Engine revving- Battery would climb to 14v but would slowly decline back down to 12.55v after a few minutes.

All in all, seems like very low voltage. I checked the terminals, and fusible link, all connections look ok and tested with the multimeter to make sure there is current.

While digging around, I noticed the alternator belt was pretty loose, so I tightened that up to spec, still did not help.

Does this point towards a bad battery or alternator thats not putting out? Since the battery is fairly new, I am thinking the alternator is about to crap out.
 
Joined
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Messages
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San Francisco
I will add that I had a broken charge lamp relay get in the way of these exact lights lighting up when they should have, so go poke at yours with the key on and confirm it doesn't buzz/click when you do. It's in the underhood fuse box.

Thanks for the advice here, I checked out the charge lamp relay with the key on, and didn't notice any noises coming from it. Although, while I was listening for that, I did hear a quiet intermittent clicking noise coming from the alternator itself. Not sure if thats normal, but could be a red flag here
 
Joined
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Messages
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Mine all came on one day, the smoke from my alternator was a good clue to the problem. Replaced it and I everything was good. Also check the wiring at the alternator plug, I once had a jiffy lube break off two of the 3 wires coming out of the alternator. Put a big hiccup in a trip my family was on.

oof that doesn't sounds fun, thanks for the heads up on that. I checked out the wiring on the alternator this morning, and everything looks ok, all connections are nice and tight. Luckily no smoke coming from it, but will be keeping an eye out for that now
 
Joined
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-Engine off- Battery reads 12.37v
-Engine running- Battery reads 12.55v
Engine off 12.3 is about 70% charged.
Engine running should be 14.4 if the alternator is putting out. You can check the terminal on the back of the alternator and that will eliminate a poor battery terminal or faulty connection.
I would bet on alternator though.
 
Joined
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Hi All,

To add closure to this thread..

-Replaced fusible links, no luck. At least I got rid of the ratty 20+ year old ones and eliminated that fire hazard :)
-Checked and cleaned all ground connections, no luck.
-Triple checked connections on battery terminals, and back of alternator, no luck.

So I sacked up this week and ordered a "new" refurbished 80a alternator from Autozone. Link here. Made sure I did not order a 90a, because IIRC I read a few threads that it would not fit due to internal fan and whatnot. Installed this morning in ~4 hours. Pretty easy job, just have to be extra careful to not knick or damage the belts. Fit perfectly, minus having to run down the the store to grab a half inch longer bolt for the bottom mount.

Put everything back together, and BOOM!! 14.6v while idling, and solid 12.6v when car is off. Runs like a champ. Windows roll up at a normal speed now, starts up faster, and most importantly the "Christmas Tree Light Effect" is gone. I didn't realize how much of a difference it would make, and kicking myself in the A$$ for not doing this sooner.

Thanks all for the time and advice here. Long live the mighty 3FE!!
 

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