Gen light question [Archive] - Chevelle Tech

: Gen light question


Geo71
Jun 28th, 10, 9:58 PM
Does this sound correct?

With the key on the GEN light is on....start engine GEN still on but not as bright.

Swapped Voltage Regulator (external on firewall). Now with the key on...GEN light is off...start engine...GEN light still off.

With engine running (800 rpm idle) There is approx 14 v at the battery and back of alt. Wire coming off the side of alt that runs over to Voltage reg is 12v.

Is this the way it should be?

Thank

pnugene
Jun 28th, 10, 10:06 PM
With external regulator, ignition on, not running, lamp should be on. Engine running, lamp should be off. If the lamp is burned out, the alternator will NOT charge the battery.

Finally
Jun 28th, 10, 10:13 PM
No, not right.

Gen light on with key in run position before starting engine. Gen light off after engine running. 14v at idle doesn't sound bad. 12v going from alt to volt regulator, which wire? Make sure voltage regulator is grounded to rad core support. Make sure it's a good clean connection. Make sure the forward light harness grounds to rad core support are clean and good connections. Also pigtail off negative battery cable to passenger fender. A bad ground will fool the Gen light circuit and cause the light to glow, been there before.

Finally
Jun 28th, 10, 10:15 PM
With external regulator, ignition on, not running, lamp should be on. Engine running, lamp should be off. If the lamp is burned out, the alternator will NOT charge the battery.

There is a resistor in parallel with the light bulb. If the bulb burns out the current flows through the resistor to field windings and the alt will still charge.

pnugene
Jun 28th, 10, 10:24 PM
There is a resistor in parallel with the light bulb. If the bulb burns out the current flows through the resistor to field windings and the alt will still charge.

Thanx for the correction. I built a homespun harness for my engine test stand and didn't know about the resistor. When my lamp got trashed the alternator quit charging. And I was thinking GM didn't cover their bases.

Geo71
Jun 28th, 10, 11:42 PM
No, not right.

Gen light on with key in run position before starting engine. Gen light off after engine running. 14v at idle doesn't sound bad. 12v going from alt to volt regulator, which wire? Make sure voltage regulator is grounded to rad core support. Make sure it's a good clean connection. Make sure the forward light harness grounds to rad core support are clean and good connections. Also pigtail off negative battery cable to passenger fender. A bad ground will fool the Gen light circuit and cause the light to glow, been there before. The gen light would come on with the key in the on position before changing the regulator. Now it won't come on. I know the bulb works (or at least did).

The 12 volt reading is on the blue wire that is spliced in with the white wire coming out the side of the alternator (small plug with two wires). It runs over to the regulator 4 pin connector.

I didn't change the little metal can that plugs in to the reg though.

I did add the neg battery pigtail yesterday.

Geo71
Jun 28th, 10, 11:43 PM
With external regulator, ignition on, not running, lamp should be on. Engine running, lamp should be off. If the lamp is burned out, the alternator will NOT charge the battery.The bulb did work unless it blew out for some reason.

pnugene
Jun 28th, 10, 11:49 PM
The new regulator may have failed if you ran it without the regulator ground wire.

Geo71
Jun 28th, 10, 11:50 PM
The new regulator may have failed if you ran it without the regulator ground wire.Which wire is that? I hooked up the new one just like the old one.

Finally
Jun 29th, 10, 7:49 AM
Check the bulb. If you're reading 14v at the bat and alt while idling the alt is working. Run the engine up a little and see if the voltage goes up, shouldn't go up much, 14 to 14.5 is about right.

Geo71
Jun 29th, 10, 8:54 AM
Check the bulb. If you're reading 14v at the bat and alt while idling the alt is working. Run the engine up a little and see if the voltage goes up, shouldn't go up much, 14 to 14.5 is about right.I'll check it out later today and see what i can find out. There were a couple wires that attached to the bolt closest to the headlight side. That wouldn't be a ground wire for that bulb would it?

Thanks for all your help! You are a lifesaver :)

Checked out your car pics....very nice!

861_ford
Jun 29th, 10, 12:13 PM
a bad connection at the alternator plugin will also cause the gen light to remain lit after the engine starts. been there; done that.

Finally
Jun 29th, 10, 5:54 PM
I'll check it out later today and see what i can find out. There were a couple wires that attached to the bolt closest to the headlight side. That wouldn't be a ground wire for that bulb would it?

Thanks for all your help! You are a lifesaver :)

Checked out your car pics....very nice!

Thanks. Are you talking about wires that attach to voltage regulator bolt? Those are ground wires for the headlights.

Geo71
Jun 29th, 10, 6:02 PM
Thanks. Are you talking about wires that attach to voltage regulator bolt? Those are ground wires for the headlights.Yes those wires. I thought that was what they were going to. There were those two attached to that bolt, then on the other top bolt a small metal can that plugs in the back of the regulator. I reused that can, since the new regulator didn't come with another one.

Finally
Jun 29th, 10, 6:09 PM
That all sounds ok. Like I said check the voltage at higher rpm and the bulb. With 14v at the battery your alt is charging.

Geo71
Jun 29th, 10, 10:17 PM
That all sounds ok. Like I said check the voltage at higher rpm and the bulb. With 14v at the battery your alt is charging. Well not going well.......I could not get to the bulb and the battery was too low to start the car. It's on the charger right now.

On to the testing.....jump started it too at least see what was going on and got the same readings as before....no engine light on at any time.

Swapped back to the old regulator and with the key in run position, the light was back on. So the bulb must be ok.

While running the gen light is still on, not quite as bright.

Testing the system I came up with this....

At the battery: 13.2 at 800
13.9 at 1500

Back of alternator: same on both

Junction of Blue wire and white wire coming out of the side alt connector 11.9 at 800
11.2 at 1500

Geo71
Jun 29th, 10, 10:41 PM
Here's a pic of the alt wiring.

Finally
Jun 30th, 10, 7:43 AM
That pictures tells a lot. That's an internally regulated alternator, you don't need an external voltage regulator. I'm guessing the regulator you have, old one, has been jumpered inside for use with the alt you have. The white wire gets 12v through the old regulator when the key is on. That turns on the internal voltage regulator. The red wire is the sense wire for the internal alt, it senses the output voltage and tries to keep it at the correct voltage. Having the sense wire right on the back of the alt is not the best. It should run over to the horn relay/main splice area so it senses voltage there, it could be a few volts lower at the main splice then at the back of the alt. Wouldn't worry about it now.

Those voltage readings are too low. Take the alt off and have it tested at an auto parts store

Geo71
Jun 30th, 10, 8:24 AM
That pictures tells a lot. That's an internally regulated alternator, you don't need an external voltage regulator. I'm guessing the regulator you have, old one, has been jumpered inside for use with the alt you have. The white wire gets 12v through the old regulator when the key is on. That turns on the internal voltage regulator. The red wire is the sense wire for the internal alt, it senses the output voltage and tries to keep it at the correct voltage. Having the sense wire right on the back of the alt is not the best. It should run over to the horn relay/main splice area so it senses voltage there, it could be a few volts lower at the main splice then at the back of the alt. Wouldn't worry about it now.

Those voltage readings are too low. Take the alt off and have it tested at an auto parts storeAhh....maybe that is why the blue and brown wires at the reg connector were cut and twisted together? I had returned them to the connector spots. I should return those the way they were? The Gen light was on before i did that though.

I'll take the alt off Friday and get it tested somewhere. Then move the sense wire to the horn relay.

Finally
Jun 30th, 10, 10:43 AM
Yes the blue and brown should be connected together at the old regulator when using an internally regulated alt. Put those back like they were and do the voltage readings. The way it is right now your alt isn't turning on at all. There should also be a white wire coming from the old voltage regulator over to the alternator. You can connect that to the small red wire that is connected to the output stud now. At the old regulator connect the other end of that white wire to the wire that is on terminal #3 of the regulator, disconnect from regulator. That wire ties into the main splice. The old regulator used that as it's sense wire.

Geo71
Jul 2nd, 10, 9:24 AM
Yes the blue and brown should be connected together at the old regulator when using an internally regulated alt. Put those back like they were and do the voltage readings. The way it is right now your alt isn't turning on at all. There should also be a white wire coming from the old voltage regulator over to the alternator. You can connect that to the small red wire that is connected to the output stud now. At the old regulator connect the other end of that white wire to the wire that is on terminal #3 of the regulator, disconnect from regulator. That wire ties into the main splice. The old regulator used that as it's sense wire.Excellent. I'll try this today and see how it comes out.

On the small red wire attached to the back of the alt...do i leave it connected to the alt along with the white?

aawtech
Jul 2nd, 10, 9:38 AM
Excellent. I'll try this today and see how it comes out.

On the small red wire attached to the back of the alt...do i leave it connected to the alt along with the white?

The white wire should jumper over to the brown wire (that is the exciter wire for your system and is also the bulb check default for your gen light) on your voltage regulator and the red should jumper over to the battery post on the alternator or all the way back to the red at the voltage regulator. If the white is hook with the red, it will drain your battery and also destroy the alternator as the internal regulator will be on all the time which will also drain your battery.

Donny

Geo71
Jul 2nd, 10, 5:09 PM
The white wire should jumper over to the brown wire (that is the exciter wire for your system and is also the bulb check default for your gen light) on your voltage regulator and the red should jumper over to the battery post on the alternator or all the way back to the red at the voltage regulator. If the white is hook with the red, it will drain your battery and also destroy the alternator as the internal regulator will be on all the time which will also drain your battery.

DonnyGoing to dive in after work and see if I can get this working. Then to dive into the steering box upgrade. :)

Geo71
Jul 2nd, 10, 10:07 PM
Ok so I messed with it tonite.

Re-wired like this:

Back of alt

....small wire from pos battery cable along with big red wire. Not sure where the red wire goes to....

side of alt connector....

white out of connector to blue (runs over to reg)
red out of connector to white (runs over to reg)

at reg....blue connected to brown

white connected to red (has fusible link)

Voltage readings at idle

battery 14.2
back of alt 14.2
side connector (white to blue junction) 12.1
(red to white) 14.2

no change at higher idle and gen light on in run pos...still on but dim in running position.
_____________________________________________

Then I rewired it I think like Donny suggested (if I have it correct)

Back of alt is the same battery pos small wire along with bigger red wire.

Side connector is now this:

white out of connector to white over to reg
red out of connector to blue over to reg

at the reg is now this:

blue hooked to red with the fusible link
white to brown.

voltage readings at battery are 14.1v
back of alt 14.1v
red/ blue is 14.1
white/ white is 11.9 at higher engine speed this goes to 13.5v

Now the Gen lite is on in run postion as before and on dim while running. When increasing the engine speed to 1200 the light goes out. Once the engine goes back to idle it comes back on but still dim.

What do you think? Do you need pics of the wiring?

stellar
Jul 3rd, 10, 4:02 PM
bad diode trio in alt. repair alt or replace.

Geo71
Jul 12th, 10, 9:16 AM
I took the alternator out and over to Autozone. They put it on their tester and it passed. It was tested twice.

Put it back in the car. With the engine running the gen light is still on faintly at idle and goes off when the rpms are higher than 1200 or so. Doesn't seem to make any difference with the headlights on or off.

stellar
Jul 12th, 10, 11:07 AM
Make sure belt is tight and connections good. High resistance caused by corrosion can cause the same symptoms. If wires and belt check out OK change alt.

Geo71
Jul 12th, 10, 11:45 AM
Make sure belt is tight and connections good. High resistance caused by corrosion can cause the same symptoms. If wires and belt check out OK change alt.It is a bit crusty in appearance. More investigating coming up. :)

I did finally get to take it down the road yesterday! Pretty good afternoon all in all.