Gen1 Light stays on and oil light with engine OFF. Any ideas?

[w5ood]

Got in the truck today and my wife said something was burning. I could smell it as well. I checked under the hood and could not see any wires melted or smoke when we got to the store. I turn off the truck and the gen1 light is glowing. We go straight home and no more smell but when I turn the truck off gen1 stays lit and now oil light is on. Funny thing is they go off when the truck is running. I know they all share the 20amp fuse in slot 5 but what are yalls thoughts. Where should I start? Can the alternator failing inside cause this issue? I dont think I have rebuilt gen1 alt so I was going to just do that first but any tips on a starting spot would be appreciated. Ive never seen the lights come on with the key off. I did unhook the batteries until I can get it figured out.

 

[WWRD99]

Got in the truck today and my wife said something was burning. I could smell it as well. I checked under the hood and could not see any wires melted or smoke when we got to the store. I turn off the truck and the gen1 light is glowing. We go straight home and no more smell but when I turn the truck off gen1 stays lit and now oil light is on. Funny thing is they go off when the truck is running. I know they all share the 20amp fuse in slot 5 but what are yalls thoughts. Where should I start? Can the alternator failing inside cause this issue? I dont think I have rebuilt gen1 alt so I was going to just do that first but any tips on a starting spot would be appreciated. Ive never seen the lights come on with the key off. I did unhook the batteries until I can get it figured out.

I'm not exactly sure where but it sounds like something is grounded out and my guess is in the alternator pack...a diode probably is not stopping power flowing one way so when you turn off the key it's allowing power through for the lights but not when running because it's trying to make power...not sure if the oil light is on the same circuit though...other thing possibly is the ignition switch on the column isn't adjusted right or skipping power and not turning off everything with the key...like it'sin accessory or on...that would be easy to check just unplug it!! It could be that simple.

Sent from my SM-G955U using Tapatalk

 

[w5ood]

I'm not exactly sure where but it sounds like something is grounded out and my guess is in the alternator pack...a diode probably is not stopping power flowing one way so when you turn off the key it's allowing power through for the lights but not when running because it's trying to make power...not sure if the oil light is on the same circuit though...other thing possibly is the ignition switch on the column isn't adjusted right or skipping power and not turning off everything with the key...like it'sin accessory or on...that would be easy to check just unplug it!! It could be that simple.

Sent from my SM-G955U using Tapatalk

Yea I think its the alt as well but I wanted others to chime in 2 brains are better than 1 and hundreds is great. The reason I think its the alt is that my volt meter is no longer reading in the green. Just on the line between green and yellow as if one alt is working and the other is not. Ive found with these trucks the alt rebuild fixes a lot of issues if the wiring has not been molested. Thanks for the reply I think Ill order a rebuild kit and start there.

 

[WWRD99]

Yea I think its the alt as well but I wanted others to chime in 2 brains are better than 1 and hundreds is great. The reason I think its the alt is that my volt meter is no longer reading in the green. Just on the line between green and yellow as if one alt is working and the other is not. Ive found with these trucks the alt rebuild fixes a lot of issues if the wiring has not been molested. Thanks for the reply I think Ill order a rebuild kit and start there.

My truck I just got does that now...when I first start it gen 2 light stays on until I rev it a little and the volt gauge is on the line! I'll be doing that one and see if it goes green...might do both just to make sure!

Sent from my SM-G955U using Tapatalk

 

[Barrman]

The oil light is tested by grounding it with the ignition on. If it lights then the wiring is good. So, yours is coming on when the ignition is off and the lead is supposed to be connected to the oil psi sender. It is grounding somewhere.

At the same time, the oil light circuit is getting power with the ignition off. Basically think of a light bulb sitting on a table with a red wire going to a power source and a black wire to ground. They both have to do their thing for the light to turn on. The above paragraph is dealing with the black wire. Now you have to find out why the red wire is getting power with the key off.

I think you have some melted or fused wires somewhere. Separate and follow the oil wire from the sender on the drivers rear of the block to the through the firewall plug at the extreme drivers side firewall. If it looks good. Us a 10 mm socket and separate the firewall through plug. Look for arcing or bent blades. If it all looks good then you get to go under the dash. But at this point I think following the alternator issues under the hood should be done.

They probably are connected issues as thought about in previous post. But, since they are such different systems my thought was the 1 wire oil sender might be easier to follow and look for issues than the several wires for the alternator.

 

[ezgn]

My truck I just got does that now...when I first start it gen 2 light stays on until I rev it a little and the volt gauge is on the line! I'll be doing that one and see if it goes green...might do both just to make sure!

Sent from my SM-G955U using Tapatalk

Check all the connections to the alternator. Pull the electrical connections apart and clean all the black gunk out of the connectors. Better yet if the connectors are full of the black gunk these trucks are famous for, replace the connections with new ones.

 

[dougco1]

Got in the truck today and my wife said something was burning. I could smell it as well. I checked under the hood and could not see any wires melted or smoke when we got to the store. I turn off the truck and the gen1 light is glowing. We go straight home and no more smell but when I turn the truck off gen1 stays lit and now oil light is on. Funny thing is they go off when the truck is running. I know they all share the 20amp fuse in slot 5 but what are yalls thoughts. Where should I start? Can the alternator failing inside cause this issue? I dont think I have rebuilt gen1 alt so I was going to just do that first but any tips on a starting spot would be appreciated. Ive never seen the lights come on with the key off. I did unhook the batteries until I can get it figured out.

Time for a new or rebuilt alternator. I had the same thing happen to me last summer. Just keep the batteries disconnected till you repair/replace it

 

[w5ood]

Well Im feel pretty stupid or at least old. I got some time this weekend to look at the truck, and to my surprise and delight its missing a belt. I didnt even notice it when I checked it before. I am so used to it being something more complicated like fusible link or rebuilding the alt. I completely overlooked the dang belt. Easy fix lets hope!! Thanks for all the advice. I still learned a little something in the replies so thank you for that guys.

 

[LT67]

My truck I just got does that now...when I first start it gen 2 light stays on until I rev it a little and the volt gauge is on the line! I'll be doing that one and see if it goes green...might do both just to make sure!

Sent from my SM-G955U using Tapatalk

The gen 2 light coming on when a cucv is started and going out when you tap the throttle is normal

 

[Matt S]

Well Im feel pretty stupid or at least old. I got some time this weekend to look at the truck, and to my surprise and delight its missing a belt. I didnt even notice it when I checked it before. I am so used to it being something more complicated like fusible link or rebuilding the alt. I completely overlooked the dang belt. Easy fix lets hope!! Thanks for all the advice. I still learned a little something in the replies so thank you for that guys.

Oh man that's funny because that exact same thing happen to me but I was driving down the highway at the time and heard the belt depart the engine compartment and the light came on. From the sound and the timing of the light coming on, I had a location to look.

 

[w5ood]

Well Im not as dumb or old as I thought. It appears the alt is bad. I noticed when it was running with the new belt the lights went off, but as soon as I turned off the truck the lights came on again. I unplugged the red wire from the back of the driver side alt and the lights went off. I noticed when it was running it looked like the alt was spinning slower than the other one. I also noticed the last belt had melted into the pulley. When I touched the pulley after running for only 5 minutes it was on fire!! I tested the power output and it was only putting out about 11.75 volts. I am assuming the bearings are bad in this alt causing the heat which probably fried the insides and melted the belt. Anyhow thats my best guess as to what caused the issues. I still dont know enough about the wiring to know what failing in the alt would cause power to flow to the lights. But Ill leave that to you guru's for now.

 

[WWRD99]

Well Im not as dumb or old as I thought. It appears the alt is bad. I noticed when it was running with the new belt the lights went off, but as soon as I turned off the truck the lights came on again. I unplugged the red wire from the back of the driver side alt and the lights went off. I noticed when it was running it looked like the alt was spinning slower than the other one. I also noticed the last belt had melted into the pulley. When I touched the pulley after running for only 5 minutes it was on fire!! I tested the power output and it was only putting out about 11.75 volts. I am assuming the bearings are bad in this alt causing the heat which probably fried the insides and melted the belt. Anyhow thats my best guess as to what caused the issues. I still dont know enough about the wiring to know what failing in the alt would cause power to flow to the lights. But Ill leave that to you guru's for now.

I just got 2 rebuild kits online from alternator and starter parts wholesale...I called and he had them in stock...not very expensive and came with the bearings and all the internal parts.

 

[Ferroequinologist]

Mine just did this to me too. Was working on it in the garage, went to dinner, came home and noticed a glow... was a bad driver side alternator diode. Had it rebuilt and all is good now. Glad you got it figured out.