Alternator/ Battery Question (1 Viewer)

[jrmudder92]

Long story short. I put a new reman Toyota alternator in my Lexus. it was only charging 13.5 all the time even with loads on. But when I would come to a stop it would drop down to 12.7 or 12.8 and stay there until I started moving again. So I figured I got a bad reman unit so I order another one. Before putting the new one and I had it tested and it failed. I figured being a Toyota reman it would be a good choice but it seems like it’s not. I also have a dual battery set up with a Tmax controller. So basically my questions are.

What is the normal voltage it is supposed to run and idle at?

Is there such a thing where the alternator will stop putting out a full 14 if it senses the batteries are charged?

Maybe my battery’s are bad or one is?

I have a feeling it’s a wiring problem maybe. If it is wiring what could it be? Positive cable or grounding?

 

[nissanh]

I got no dual batteries in any of my cars/trucks. With AC at full, headlights on and with wipers on at idle, I am getting around 13V and with slight increase in engine speed it climbs to 14 V. All my toyota's got OEM factory alternators with new OEM brush kit.

The batteries are fully charged yet alternator gives 14 V.

 

[jrmudder92]

Thanks for the reply. The battery’s tested fine. I’m going to try and run a new positive and negative wire to the alternator. See where that gets me..

 

[vman07]

I get about 13.5 at idle, engine warm with loads. I have a fresh alt. And battery plus a second battery. Dropping below 13.0 seems low.

Also I would only trust a dedicated volt meter to give you info. Don't rely on dash volt meter or anything blue tooth like the torque app. My torque app reports consistently low volts compared to an accurate handheld voltmeter...

 

[jrmudder92]

I get about 13.5 at idle, engine warm with loads. I have a fresh alt. And battery plus a second battery. Dropping below 13.0 seems low.

Also I would only trust a dedicated volt meter to give you info. Don't rely on dash volt meter or anything blue tooth like the torque app. My torque app reports consistently low volts compared to an accurate handheld voltmeter...

This is with a volt meter hooked up to the battery through the cabin. It’s very jumpy. Going from 13.5 - 13.8 Just kinda lost right now

 

[flintknapper]

I get about 13.5 at idle, engine warm with loads. I have a fresh alt. And battery plus a second battery. Dropping below 13.0 seems low.

Also I would only trust a dedicated volt meter to give you info. Don't rely on dash volt meter or anything blue tooth like the torque app. My torque app reports consistently low volts compared to an accurate handheld voltmeter...

^^^^ This is consistent with what mine does as well. I have a relatively new alternator (year old), good battery, cables, etc....

At idle with A/C on and other items...it will show right at 13.5 V

 

[gatormark91]

mid 13's is what my alt puts out, almost new, and I have a dual battery setup as well.

 

[jrmudder92]

If I run a positive cable from the alternator to the battery where should I hook it up at the battery? On the post? With or with out a fuse? Or on the fuse block that says alt?

 

[gatormark91]

If I run a positive cable from the alternator to the battery where should I hook it up at the battery? On the post? With or with out a fuse? Or on the fuse block that says alt?

You don’t run a wire from the alt to the second battery. You attached the positive terminals to each other, with the battery management device in the middle. Leave the factory charging going to the original battery only.

 

[05JLX470]

If I run a positive cable from the alternator to the battery where should I hook it up at the battery? On the post? With or with out a fuse? Or on the fuse block that says alt?

I would run a direct line from the battery post to the alt. post. This way you will eliminate any/all connections that could be causing problems. If you still see issues, then start narrowing things down.

 

[Spike555]

Toyota does not reman the alternators, someone else does. They just charge you Toyota prices.

 

[jrmudder92]

I would run a direct line from the battery post to the alt. post. This way you will eliminate any/all connections that could be causing problems. If you still see issues, then start narrowing things down.

Would you fuse it or just a straight hook up?

 

[gatormark91]

Would you fuse it or just a straight hook up?

Disconnect the second battery from the primary, completely. Test the voltage at the primary battery pole with the ignition off. Test it with ignition on. That will tell you how healthy alt is and if it is charging the battery. Then check it after the fusible link, to see if that is an issue.

 

[Gromulin]

I put in a reman Denso recently and get 14.1 at startup / idle. Are your dual batts isolated? Have you tried just running one at a time and see if there is a difference? The stock alternator for my 2000LC was supposed to be rated for 80A, but because of something with California models, it was actually a 100A. Anything around 13v is just life support for the battery, not charging.

 

[jrmudder92]

Second battery has been disconnected along with ever other accessory. Still 13.5. I wanna hook up this cable from the alternator to the battery but need to know if I should hook up a fuse or not????? I’ve also have ran two more grounds that has helped a good bit not dipping like before as bad. Ran one from the alternator negative stud to the negative terminal on the battery and one from the Negative on the battery to the engine.

 

[bjarnep]

The original cable set up works in thousands of Cruisers, so unless tangled with, damaged or replaced by something else, your problem must be somewhere else.
The measurement you do, is with an external calibrated meter? Except for the measurement - do you have any problems starting or other indicators that you have an electrical problem?

 

[jrmudder92]

UPDATE-- Ran a new power wire from alternator to battery with a 150 amp fuse. Also a negative wire from alternator to battery. Both wires were 2 gauge. All problems are resolved as of now. Will update if anything changes!!

 

[jrmudder92]

Solved!! Answer Major Charging Issue Need Help post #55