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1983 Toyota Pickup - charging system isn’t charging battery

my 1983 TOYOTA PICKUP 4x4 the charging system wont charge my battery even though its brand new battery and alternator, recently even bought a new wiring harness and some relays along with a regulator and checked all fuses… i dont know what else is left to do

Well, start by telling us more about the pickup. Miles on it, engine, transmission, are you doing this yourself? Why do you think it isn’t charging? In other words, what diagnostics did you do to determine it isn’t charging? What problems did you have to change the alternator and battery? What voltage does the battery show truck not running? What voltage does the truck show when running?

Does the v-belt that drives the alternator have correct tension . . . ?

Well its only has 128,278 miles on it it’s a 22r engine barely got rebuilt and its manual transmission. Yes I am doing this by myself and it isn’t charging because when I check the voltage on the battery it reads 12.47 volts and when i rev it it slowly drops and if the alternator were to be working it should go up to 14.1v
So yea and like also has a new wiring harness

It sounds like the alternator isn’t working, or the wires that connect it to the battery. Check them for continuity and the output of the alternator directly.

I have an '87 2wd; the tension on the alternator belt loosened so it didn’t charge the battery. I just had to move the alternator out about a millimeter. But I knew that because the belt screeched.

Well aside from asking you the normal questions of whether the alternator is installed properly, belt tension checked and electrical connections to the alternator etc… Im sorry to say that the introduction of a new wire harness opens up a host of possible reasons this unit isnt charging. Too many places to go with that really.

The alternator needs the direct connection to the battery obviously…but it also needs to energize the stator inside. If you have an old voltage regulator, that also needs correct wiring to let all of this work in unison to charge the battery.

In your instance I would go through the new wire harness and ID all the wires it has and be sure they are doing what they are supposed to be doing. Especially at the voltage regulator. Confirm continuity, voltage and also ground on all the wires associated with the alternator and voltage regulator… Your problem most likely resides somewhere in there. Where? We cannot tell you since the harness was changed, so in essence, everything was altered…you need to verify all those wires work.

Does the truck have a battery/alternator light, and is it working? Not sure if your truck is wired this way, but in some older American vehicles, the alternator will not energize if this light is missing or burned out.

Check for field voltage at the alternator - doesn’t have to be running, just ignition ON. No field power means no alternator output and you have a bad harness connection.

If you have field power, start it and check the output voltage AT the alternator. 14V? Bad harness again because the voltage is not getting to the battery. No 14V? Bad alternator - it happens, return it and get another.

Do you have a fusible link in addition to the “checked all fuses”?
My '79 Celica 20r engine’s alternator has a fusible link connected to the “B” terminal on the alternator. It’s listed as one of the possible causes of no charging in the FSM book.

By following Mustagman’s good advice, and testing right at the alternator, you’d be bypassing any fusible link between ALT and car’s electric.

Did the alternator charging ever work ? If so, what’s changed between the time it worked and now. I have an older Corolla and one day years ago the alternator light turned on and measurements showed the alternator wasn’t charging the battery at all. That turned out to be a splice in the the big thick wire between the alternator and the battery had been eaten by battery acid that decanted off the top of the battery and into the wiring harness to the point it became an open circuit. So make sure you have low ohm connection between the alternator output and the battery positive.

Good suggestion. IIRC my 1979 Toyota 4X4 with 20R had fusible links alongside the fat cable at the battery.

Well lon GB story short in did my research and there are two type of alternators a type b and a I had a A and it would always fry my regulator and I found out it wasn’t that alternator I needed. So I went back to the part store and got a new set of regulator and type B alternator and it charges fairly

Can you be a little more specific?

At least 13.5V at idle?

Glad you got your pickup’s alternator working again. There’s probably only a few basic alternator designs available from the vendors who build/rebuild them, and you just got handed the wrong type for some reason. Sometimes they parts store will sell one, and the purchaser decides they don’t want it after all and brings it back for some reason in the wrong box, so it gets stocked on the wrong shelf.