[dohman]

1979 long-bed, 20r engine.

Firstly, if anyone has or knows where I can find a wiring diagram that would be awesome.

My yota has been reliable and a great runner for 2.5 years ish. Recently it started cooking the battery and bubbling the acid. Tested it and it was getting 17.5v to the battery. Now I have replaced the voltage reg, cleaned all the contacts, changed the batt clamps, the alternator belt, and had the alternator itself tested (I don't know how much I should trust major retail auto parts stores...?).

Now I am getting 12.5-13v to the battery which isn't enough. So I went from too much to enough. Even if I put the old volt reg back on it still undercharges. I have checked all the ground wires I can find.

I am baffled and about ready to give up, the fact that I have seen posts about this on other sites is even more discouraging.

Someone save me... Pleas...

 

[myyota]

Are you sure the alternator is good ?, it sounds like your alternator is on its way out. when they test the alternator it can show that its good because its not under a load, but under load it can act totally different, as far as charging to much or not enough.

 

[dohman]

Well it was tested by carquest, like I said I don't know how much I trust that testing but here is what happened.

I took the alternator in, the guy at carquest hooked it up to his testing equipment. He runs test #1 and everything is peachy, he then runs some mysterious test #2 which peaks the meters and makes all the gauge lights burn as bright as the sun.

So at that point we are thinking the alternator is toast, but I have him pull a refurb'd one off the shelf and test it. It tested the exact same way as the one I have. So either mine is fine, or they are both hosed. Chances of a refurb'd alternator being hose probably aren't all that unlikely? I dunno.

ANY input is helpful, I'm about ready to scrap the whole thing and sell it for as much as I can, then buy something different.

I used to love my yota.

 

[myyota]

Are you getting the 12.5 - 13 volts at the battery with the engine running or with it off ?.

 

[dohman]

With the engine running.

 

[myyota]

It still sounds to me like the alternator is going bad. you said you replaced the voltage regulator (with a new one ?), all the voltage regulator does is regulate the voltage in the electrical system and it gets its power from the alternator, so to me it seems like it comes down to a bad or weak alternator output. Have you checked all of the ground wires in the engine area ?. You might want to do what i did, i ran a heavy gauge ground wire from the negative battery terminal to the engine block, it made a noticable improvement, otherwise the ground is running through the body before it gets back to the battery.