Alternator exciter charge?
I'm having a problem with my alt charging my battery. After multiple alt and battery replacements, I've narrowed it down to the exciter circuit not signalling.
12V is present at the 2 outer wires of the 3 pin connector but never at the center red when key is on. My understanding is that this is fed through the charge light circuit, which won't illuminate. After tearing the dash apart I found 12V at the charge bulb but no light. Switched with a known working one from blinker and still no go. How is this possible with battery voltage present? Anyone ever have issues with these speedos shorting out. Any help will be appreciated. Thanks |
Exciter charge?
The red wire (IG, pin 2) should have battery voltage through the Engine fuse with key-on. This does NOT go through the "ALT light" circuit. That's the Yellow wire (L, pin 1), which should be at ground when the alternator is not turning. (For completeness, the white wire, S ("sense") is at battery voltage ALL the time.) There is, of course, battery voltage at the "alt light" bulb with key-on. When the alternator is not turning, the L (yellow) wire is at ground, so current flows through the bulb, illuminating it. Once the alternator starts generating power, the L wire rises to about 14.1 volts (as does the battery). With the same voltage on either side of the bulb, the alt light goes out. Start by disconnecting the connector from the alternator. With your voltmeter to ground, you should have battery voltage on S (white) all the time. You should have battery voltage on IG (red) with key on. With the connector out, you will also get battery voltage (through the Alt light) on L (yellow). If you don't have battery voltage on the red wire (pin 2), you have a wiring problem (or maybe only a blown Engine fuse.) |
Originally Posted by scope103
(Post 52419512)
Exciter charge?
The red wire (IG, pin 2) should have battery voltage through the Engine fuse with key-on. This does NOT go through the "ALT light" circuit. That's the Yellow wire (L, pin 1), which should be at ground when the alternator is not turning. (For completeness, the white wire, S ("sense") is at battery voltage ALL the time.) There is, of course, battery voltage at the "alt light" bulb with key-on. When the alternator is not turning, the L (yellow) wire is at ground, so current flows through the bulb, illuminating it. Once the alternator starts generating power, the L wire rises to about 14.1 volts (as does the battery). With the same voltage on either side of the bulb, the alt light goes out. Start by disconnecting the connector from the alternator. With your voltmeter to ground, you should have battery voltage on S (white) all the time. You should have battery voltage on IG (red) with key on. With the connector out, you will also get battery voltage (through the Alt light) on L (yellow). If you don't have battery voltage on the red wire (pin 2), you have a wiring problem (or maybe only a blown Engine fuse.) Where does the voltage that illumates the charge bulb come from. And what correlation does it have to the red exciter wire. I find it odd that 12V being at the bulb and it not illuminating and 12V not reaching the exciter ciruit have nothing to do with the each other. |
The battery voltage on the alt light is from IG2 through the IGN fuse. The battery voltage on the IG (red) wire is from IG1 through the ENGINE fuse. The reason your ALT light is not lighting (if it has battery voltage on one side) is because you DON'T have ground on the other side. That ground is supposed to be through the yellow wire to L. So it sounds like you have a wiring problem.
But as I said, your multimeter will give you the answer. |
Originally Posted by scope103
(Post 52419517)
The battery voltage on the alt light is from IG2 through the IGN fuse. The battery voltage on the IG (red) wire is from IG1 through the ENGINE fuse. The reason your ALT light is not lighting (if it has battery voltage on one side) is because you DON'T have ground on the other side. That ground is supposed to be through the yellow wire to L. So it sounds like you have a wiring problem.
But as I said, your multimeter will give you the answer. |
Originally Posted by yota tay
(Post 52419522)
... That yellow wire must be the common in this circuit.
Shouldn't be. The "common" is the case ground. So far as I know, you can run the alternator with the yellow wire disconnected. |
Originally Posted by scope103
(Post 52419529)
?
Shouldn't be. The "common" is the case ground. So far as I know, you can run the alternator with the yellow wire disconnected. |
As Scope says^^^...
Correct. The charging circuit will work even without the "L" wire connected. (Excitation through charge fault light belongs on the GM system - which is not reliable - what if charge light bulb burns out?) O.P., Please put everything back to stock and do voltage checks as Scope says above. Illustrated here: https://www.yotatech.com/forums/f116.../#post52401963 |
[QUoOTE=RAD4Runner;52419542]Put everything back to stock and do voltage checks as Scope says^^^
Illustrated here: https://www.yotatech.com/forums/f116.../#post52401963[/QUOTE] Thanks for the diagram. My issue has to be at the turn hazard switch based on the diagram. Will check it out this weekend. |
Originally Posted by yota tay
(Post 52419543)
[QUoOTE=RAD4Runner;52419542]...Thanks for the diagram. My issue has to be at the turn hazard switch...
Toyota did not have the most brilliant electrical* engineers back in those days. They named the fuse "Charge" fuse when it did not power the charging circuit. They took power for the "TURN" signals, the backup lights - that you can remove completely and not affect engine function - , etc from the engine fuse. DUH! https://cimg1.ibsrv.net/gimg/www.yot...1b2185b57f.jpg *Toyota definitely had much better mechanical engineers than electrical engineers back then. :) |
Originally Posted by RAD4Runner
(Post 52419545)
If you're not getting 12V on red IG wire at alternator connector, AND also having issue with TURN signal but BUT NOT hazards, most likely issue is Engine Fuse circuit.
Toyota did not have the most brilliant electrical* engineers back in those days. They named the fuse "Charge" fuse when it did not power the charging circuit. They took power for the "TURN" signals, the backup lights - that you can remove completely and not affect engine function - , etc from the engine fuse. DUH! https://cimg1.ibsrv.net/gimg/www.yot...1b2185b57f.jpg *Toyota definitely had much better mechanical engineers than electrical engineers back then. :) https://youtu.be/8xurr79YW98 |
Please always indicate what you're working on (See signature)
Originally Posted by yota tay
(Post 52419546)
Before my alt quit the first time I was having a turn signal/ overdrive issue that was blowing the 15 amp fuse. Removed flasher relay and reinstalled and fuse never blew after that. Now it seems that something in that area is malfunctioning messing with the red wire signal. Will probably replace the whole wire.
|
I think Yota Tay is driving a '94 (yes, Rad4Runner already asked him to put his vehicle info in his signature). My EWD for a '94 shows the backup lights powered from the CIG fuse (tail lights on the TAIL fuse, turn signals on the TURN fuse). The ENGINE fuse powers the IG terminal (red wire) of the alternator, and the Cruise ECU (I didn't see anything else on the ENGINE fuse, but someone may know better).
In other words, we're all wasting our time until Yota Tay puts his multimeter to ground on the tabs on top of his ENGINE fuse. If that's blown, I wouldn't expect the alternator to work. (and I would check that fuse and circuit long before I replaced a battery or alternator, but that's just me. And anyone following the FSM.) |
Originally Posted by scope103
(Post 52419548)
I think Yota Tay is driving a '94 (yes, Rad4Runner already asked him to put his vehicle info in his signature). My EWD for a '94 shows the backup lights powered from the CIG fuse (tail lights on the TAIL fuse, turn signals on the TURN fuse). The ENGINE fuse powers the IG terminal (red wire) of the alternator, and the Cruise ECU (I didn't see anything else on the ENGINE fuse, but someone may know better).
In other words, we're all wasting our time until Yota Tay puts his multimeter to ground on the tabs on top of his ENGINE fuse. If that's blown, I wouldn't expect the alternator to work. (and I would check that fuse and circuit long before I replaced a battery or alternator, but that's just me. And anyone following the FSM.) |
Originally Posted by yota tay
(Post 52419551)
...The diagram was all I needed. Thanks
|
Originally Posted by RAD4Runner
(Post 52419681)
My diagram is for 1986-1988 22RE. Not sure if exactly same as yours when it comes to the fuses part.
|
Originally Posted by yota tay
(Post 52419688)
...I wished someone would have mentioned the plug at the fuse that excites the alternator, I would have started there and it would have made troubleshooting way easier. The wire was bad right at that connector.
The key to effective troubleshooting is to understand how the system works. What is it supposed to do, what it is not doing, then figure out why it is not doing it. |
Originally Posted by scope103
(Post 52419512)
Exciter charge?
Start by disconnecting the connector from the alternator. With your voltmeter to ground, you should have battery voltage on S (white) all the time. You should have battery voltage on IG (red) with key on. With the connector out, you will also get battery voltage (through the Alt light) on L (yellow). If you don't have battery voltage on the red wire (pin 2), you have a wiring problem (or maybe only a blown Engine fuse.) (whoopse), sorry - I replied to the wrong thread here - I do not have a "DELETE button just an "EDIT" button, so now this reply is stuck here. |
All times are GMT -8. The time now is 10:03 AM. |
© 2024 MH Sub I, LLC dba Internet Brands