Alternator wont charge battery

[RichardJ]

>>Does it make a difference if I put the ground wire on the ground terminsl on the alternator versus the alternator bracket?<<

Find out if it does. Measure voltage from battery ground (battery Neg post), to the engine block, to the frame rail, to the Alt, to the radiator support, to the regulator or anything else that should be grounded. All of these things should be grounded together and you should never measure more than about a tenth of a volt between any of these things.
An ohm meter should not be used for checking ground circuits.

[RichardJ]

>>how do i check them while the connectors are still plugged in?<<

It's called back-probing. Simply slide the voltmeter probe along side the wire into the back of the connector. Easy with these type of plugs. Much harder with newer type plugs such as the '80s weather-tight plugs.
When the plugs are too tight, use a straightened paper clip to slide in alone side the wire. Still not enough room, use the straight pins you saved from a new dress shirt. As a last resort the pins can be used to pierce the insulation at a low angle. The insulation will usually pretty much self heal.
I have alligator clips that slip over the meter probes, but I bought most of them at the now defunct Radio Shack.

[Coalkracker]

Ok so Neg battery post to frame-0, to engine block-0, to radiator support-0, to alt bracket-0, to alt body-0, to VR-0, and to everythingvelse that should be grounded-0.

[Coalkracker]

Alright i tested everything i need to i think.
Batt 11.9 (obviously not fully charged)
Neg-F @ reg 11.3
Neg-2 @ reg 0
Neg-3 @ reg 11.9
Neg-4 @ reg 5.9
Neg-F @ alt 11.3
Neg-2 @ alt 0
Neg-BATT @ alt 11.9
Pos-2 @ reg 11.9
Pos-2 @ alt 11.9

[Steeveedee]

How much would it cost to take your truck to a shop for a diagnosis? You've already paid for an alternator and regulator that you have not demonstrated needed replacing. Please stop throwing money at it and get a proper diagnosis.

[Coalkracker]

Its not on the road yet so thats not an option. The guy from the parts store told me to bring one of the alternators back tomorrow so i'll be getting my money back from that. The old regulator was over 30 years old so i probably was going to need a new one soon anyways. So im not really throwing money at it, more like throwing a lot of my time at it but i need to learn about how everything works on this truck anyway so it'll be worth it.

[RichardJ]

OK, what is the "Neg-" ? Voltages would be written as 11.3 V without polarity notation, unless the device has both + and - voltages. 0 is written as 0.0 V


What is the "Neg-2" @ alt ? If you have a terminal #2 and no "R" terminal on your Alt, I can't wait to hear the explanation.

Neg-BATT @ alt........... If you have a negative ground, THE BATT TERMINAL ON THE ALT IS POSITIVE. Swap your voltmeter leads if it provides you with less confusion. On automotive electrical, RED is positive and BLACK is negative.


What is the "Pos-2" ?


Neg-F @ reg 11.3
Neg-2 @ reg 0
Neg-3 @ reg 11.9
Neg-4 @ reg 5.9
Neg-F @ alt 11.3
Neg-2 @ alt 0
Neg-BATT @ alt 11.9
Pos-2 @ reg 11.9
Pos-2 @ alt 11.9

[Coalkracker]

Neg-batt is negative terminal on battery to BATT terminal on alternator

Neg-2 @ alt is negative battery terminal to 2 terminal at alternator....the other side of 2 from the regulator

[Coalkracker]

Pos-2 is positive battery terminal to 2 terminal

[Coalkracker]

@ = at

[Coalkracker]

And i dont have a 2 on my alternator its r, that was a mistake

[RichardJ]

>>Neg-batt is negative terminal on battery to BATT terminal on alternator<<

Since you established that you have good grounds, then ground is ground and if all measurements are measured from ground, then "Neg-" only provided confusion.

>>Pos-2 is positive battery terminal to 2 terminal <<

Covered above.

Voltages are usually taken with "Key Off", with "Key On" or with "Key On, Engine Running" specified.
Were your voltages read with "Key On" and engine not running? Are the voltages on the regulator similar with the engine running?

[Coalkracker]

All of those readings that i posted last were with the engine running. Tomorrow i will have to check to see if they are similar with just the key on.

[RichardJ]

The "F" stands for "Field". The Field Voltage of 11.3 V is way more that enough to start charging, so the alternator should be charging.

At this point I would say the regulator is good, BUT you still don't know. When the Alt starts charging, the output from terminal "R" will be roughly half the charging voltage. This voltage applied to #2, should close the Field relay, shorting #3 and #4 together. #4 will then read battery voltage , the same as #3.

You said you have two alternators so take them both in for testing.

If, and I believe they will test bad, have them also test a new one. They probably don't sell or test very many 10DN alternators anymore. The test machine and/or the tester may not be up to the task.

[71CHEVYSHORTBED402]

Funny this came up, because my daughters "new" 2012 Honda Civic is giving us problems. Two guys say the battery is bad, two say good including Interstate. The alternator was replaced. In fact they did it twice after checking the first install, apparently a bad new alternator.

I can say I put the battery on a tender, showed full charge. Read 12.7, but my little meter didn't read full for some reason. Ditched that and used my multi-meter for the first time (finally). 12.7, installed battery and checked again (12.5). Not sure why that much change but OK. Drove three miles and checked again for 12.3. Let it sit a while and 12.57. Drove it to store and back 12.35. Couldn't tell you what's going on, I don't know enough about charge systems, but at this point I don't trust the battery and/or charge system.

Don't much care for Honda at this point either. Only 76K on the car, it doesn't measure up to every other newer car I've bought, being Toyotas.

[Coalkracker]

All voltages tested at the regulator are the same between key off, key on, and key on running. Hopefully this may lead me in the right direction??

[RichardJ]

>>All voltages tested at the regulator are the same between key off,<<

Ok, You're confusing me again as to what you actually have.
Provide voltages with "Key Off" on F, 2, 3, and 4.

[Coalkracker]

F 11.3v
2 0v
3 11.9v
4 5.9v

[Coalkracker]

Took alternator to get tested and it checked out fine.

[RichardJ]

#4 should be 0.0 V with the Key Off, BUT if you have 11.3 V on the Field with the engine running, regardless of anything else the Alt should be charging.

This should have been covered with the voltage readings. Pull the regulator connector OFF. Pull the Alt connector OFF. With your ohm meter, check continuity from the F wire terminal on the Reg connector TO the F wire terminal in the Alt connector.


Sorry, "Key Off"

[Coalkracker]

Ok so i have continuity through it.

[Coalkracker]

Here we go

[Steeveedee]

Where did you measure that Voltage? Looks like it is now charging!

[Coalkracker]

Yea its charging now. That was measured at the battery posts. Sprayed harnesses with electrical contact cleaner then used very small tools with little pieces of paper towel to scrape and wipe clean, went back and fouth doing that a bunch if times until they were perfectly clean then did it a few more times. New plug into alternator and soldered instead of crimped. Re-checked and re-cleaned every ground and anything else i could find and probably things that didnt need to be done but i did anyway. And it works. Now i have a battery drain someplace but i'll worry about that another day. Thanks for all the comments.

[Steeveedee]

Try disconnecting the power wire from the alternator to see if the drain goes away. I bought a rebuilt alternator recently that had a bad diode right out of the box. Killed my battery dead. When I was charging it up, I noticed that the alternator was warm to the touch, and the engine hadn't been running.