A lot of dash lights on. HDJ81 (1 Viewer)

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Joined
Jan 18, 2022
Threads
6
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Location
Austin, TX
I just got home to Texas from being out of the country and drove the truck home last night without issue. This morning all these dash lights were on and I don’t know where to even start. Temperatures are below freezing but the truck has been in colder weather without issue in the past. Anyone seen all these on at once? They are always on regardless of rpm.

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Give alternator plug a wiggle, unplug and plug it back in. While your under the hood make sure belts are present decent and tensioned. Have seen this before fear not.
 
I checked the voltages on the battery while it was running. 11.8 and 12.0 on them. Alternator not charging them. I will try what you suggested and report back. All the belts were present but I will check their tensions
 
Yep your dash voltmeter and big red charge light tells me the same, why all the rest come on I can't say but I've seen it on two other hdj81's. Can give alt a tappytaptap as well with vehicle running.
 
the belts seem to be tensioned. I took some of the intake off the truck to get more access to the plug on the back. Seems to be fully seated but all the lights are still on. To me it seems like the alternator being bad wouldn’t cause all the other lights which leads me to think something electrical is causing all of it. Could a computer going haywire cause an alternator to not send charge?
 
Got you. Yes I gave it a few good snacks and it didn’t change anything
 
Ok, 98 percent you need an alt, but lets verify shall we. Easy check is 'charge' or 'alt' fuse, may be in underhood box, may be in box in cab near your knee when seated.

If i recall alt is 3 wire plug, one is keyed power (says hey wake up), one is 'sense' voltage (determines how much to charge based on battery voltage), one turns on light when alt isnt charging (it actually supplies a ground path that doesnt exist when alt is charging).

So thats great.

If you've got power at 2 or the three wires in truck side of alt plug with key on alt is bad. *PROVIDED connectivity/pin contact/plug has been ruled out...* Can test key on and key off to see which wire is which.

A wiring diagram can tell you exactly but isnt really needed if youve been there before, there is a section on this site with digital manuals. Quite the resource but no replacement for a paper one in the truck.
 
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I know you think those lights aren't the alternator but they are. I don't know why

My plug was loose and above 75 all my lights would come one. No idea why.

And if you're seeing 12v at idle it's not charging.
 
In the interest of further diagnosis one can also "bench" test alt on the vehicle if you manually supply voltage to IG and S terminals on alt side, while monitoring voltage at big stud or battery if confident that path is ok.

Back to that plug though....
 
If you search for "christmas tree" you'll find that this is a common symptom when charging is inadequate/non-existent on all 80s (at least the older ones).

I replaced my dash bulbs with LEDs and now I get this at every startup for a few seconds until my alternator hits 12.8V output and then they go dark like clockwork. I guess somehow the resistance of the charge bulb itself is part of the circuit design and switching to an LED threw that off so now it takes a higher voltage than it used to.
 
alright sorry for the delay. It's still snowing/icing here so I was dreading getting access to the alternator plug. I had to remove intake tubing to get enough space to get the plug out. I measured all 3 lines into the alternator and got 3 voltages in the 10.5-11.8V range. Also from between the alternator and the battery while it was running I only saw 11V. I think we have identified the issue. Thanks everyone for the help. Anyone know where to get one? Partsouq looks like they don't have any. Are any other ones compatible? am I going to need a plug adaptor?
 
It's 04/1992 build date. I was looking at this one but the ship time seems long

 
just get one for a US 80 series and swap the pully.
 
Ooooodles of suitable units available, some on the shelf at a parts store near you. Pulley can be swapped with hand tools, local auto electric shop can also rebuild.
 
 
just found a Tercel alternator locally. Fished the one out of my truck today. I think the one coming out of the truck is a 80A but the largest tercel was a 70A. Anyone know what stock current rating was? Partsouq seems to suggest 60A but a lot of the replacements I see for sale online are 80A. The one that was in the truck is not the original which doesn't help to solve what the truck came with from the factory.
 

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