Alternator light question, concerned about a voltage drop an alternator light starting to come on Options

[DRPHIL914]

I am about three hours into a 5 Hour Dr. on my way to Atlanta I just noticed a little while ago maybe 10 minutes ago a slight dim Flickr or glow from my alternator light also then looking at my voltage gauge which with my lights on normal he reads 11.5 V but it now reads 10.5 phones. Also at one point I hit a bump and the light disappeared in the voltage went back up to 11.5 but then after a few minutes the voltage drop again and the light is now on very faintly but it is so here’s my question what is the most likely cause is it a loose wire somewhere is it a loose belt those are the two most likely scenarios to me but if it’s a wire what should I look for I know I’m going to have to stop to look and right now I hit a bump** edited** as I’m driving right now and the light went out . So what light is most likely loose and causing this issue I’m going to have to stop and figure it out I guess thank you for the SAP help and responses in advance, Dr. Phil
I think you can see from this picture the light is on when I turn the other lights off you can see the faint glow of the alternator light and maybe even a little bit and the other picture with the lights on

[DRPHIL914]

Anybody has an idea on this and wants to call me my cell number is 843-812-6653 also forgot to mention that the alternator was brand new Bosch 75 amp that I put it back in July the belt is new at that time as well I probably have only 250 to 300 miles on the car including since Okteenerfest since installation of those partsp

[still2slow]

All you can really do is check connections on battery first (make sure they're tight and clean) and unplug/plug back in the voltage reg to clean the spade connectors on it.

When you say you "had a bomb"... does that mean you let a fart or actually pressed a yam and the light went off?
Just trying to learn new tricks.

Good luck.

[DRPHIL914]

too funny! exuse the weird way that things get put in whennusing microphone and speaking into the talk to text thing but i was not going to text driving down road. stopped to get gas now, of course the idle is perfect, and so is voltage and no alt light right now. thanks for advice, i do have a spare voltage regulator just in case. BTW i also have a spare distributor. this one is the 123ignition and is the first trip with it in car. hope this isnt an issue with it somehow.

[worn]

too funny! exuse the weird way that things get put in whennusing microphone and speaking into the talk to text thing but i was not going to text driving down road. stopped to get gas now, of course the idle is perfect, and so is voltage and no alt light right now. thanks for advice, i do have a spare voltage regulator just in case. BTW i also have a spare distributor. this one is the 123ignition and is the first trip with it in car. hope this isnt an issue with it somehow.

When you are driving the voltage should be a bit over 13. At rest it should be a bit over 12. Something is going wrong, but slowly. If I were in your shoes I would swap out the VR and see what happens. Good luck!

[DRPHIL914]

i might swap that out tomorrow, i got here fine, 6.5 hour drive due to traffic and detours
so on. but it also would come and go, sometimes not related to any bump or jolt- maybe a loose wire or bulb? seems tight at coil. i forgot my voltage tester, i do have my timing light in the bag. just need to get to Shades tomorrow, its only 12 miles! will post pictures !

[76-914]

too funny! exuse the weird way that things get put in whennusing microphone and speaking into the talk to text thing but i was not going to text driving down road. stopped to get gas now, of course the idle is perfect, and so is voltage and no alt light right now. thanks for advice, i do have a spare voltage regulator just in case. BTW i also have a spare distributor. this one is the 123ignition and is the first trip with it in car. hope this isnt an issue with it somehow.

When you are driving the voltage should be a bit over 13. At rest it should be a bit over 12. Something is going wrong, but slowly. If I were in your shoes I would swap out the VR and see what happens. Good luck!

Unless you have the center console volt gage. 11.5 is normal with lights on if you have this set up. When checked at the battery, then yes it should be ~13v. Good luck with your return trip. FWIW, I'd wiggle the alt harness close to the relay board to see if the gremlin is in that connection. (IMG:style_emoticons/default/beerchug.gif)

[anderssj]

Dr Phil,

Not sure I remember the ground path for the alternator, but if it is grounded through the engine, then through the transmission, you may want to check where the strap from the trans grounds to the underside of the body. Just a thought. Good luck on the rest of the trip!

[DRPHIL914]

Dr Phil,

Not sure I remember the ground path for the alternator, but if it is grounded through the engine, then through the transmission, you may want to check where the strap from the trans grounds to the underside of the body. Just a thought. Good luck on the rest of the trip!

thanks for the suggestion, thats a great idea. i dont have a jack so i am not sure i can reach it , it was a new strap but need to just check the alt harness connections and geounds again, also maybe we need to check the bulb and connection on my gauge too

[Spoke]

About the grounding of the alternator, you can test the grounding with 2 simple measurements.

The important ground connection in the charging system is between the battery negative terminal (not the cable or clamp but the actual battery terminal), and the ground of the alternator plus the D- connection on the VR. D- is connected to the alternator case.

The measurements are made with the engine idling and the headlights on (for a heavy load):

1) Measure from the battery terminal and the chassis. Measure directly on the battery terminal, not the clamp. This will test the voltage loss from the battery negative connection to chassis. This measurement should be 0.0Vdc.

2) Measure the VR D- voltage at the VR connector on the relay board to chassis. This ground is a bit more complicated as it goes from the VR connector wire to the alternator case to the fan shroud to the engine case to the transmission case to its transmission ground strap. This measurement shouild be 0.0Vdc.

If you have even 0.5 Vdc or greater, you need to check the connections of the high voltage reading. These tests will show if the grounding is a issue or not.

[TheCabinetmaker]

I chased this same problem for a while. Turned out a chunk of tar on the bottom of the relay board broke off (found it on the engine shelf) and the receptacle for the voltage regulator was floating up and down and causing an intermittent continuity loss.

[DRPHIL914]

Made it home today ok , but toward the end of the drive the voltage was slowly dropping, so i checked it as soon as i got home with the volt meter and it was reading under 12, @ 11.75 wen running, and turned off 12.34 over battery terminals. came back a while later restarted it and checked again, and it was 12.15 at idle. that waa the same with both voltage regulators i have. double checked connections at the coil, battery, and relay board alt harness etc. all good.
I am beginning to think that my alternator is not making proper voltage. i remember when i first put this alternator on and put the motor back in the car in Sept and i know it was tested at over 13v at that tme. Do alternators go bad slowly like that? seams strange for a brand new one to go that fast. btw battery is only a year old

[904svo]

Try this measure the voltage between the alternator case and the engine case. You
should not be any voltage measured if you due. You have a grounding problem between
the alternator and the engine casr.

[davep]

The alternator grounds through its case, then through the mounts and into the fan shroud. If there is too much paint then it is possible there is a poor connection. On the other end I had a problem where the ground stud for the battery strap was solid, but the car body did not carry the current well. I used a second ground strap from the battery post clamp to an existing hole in the fan shroud near the coil; 8mm bolt & nut. To check the state of the ground circuit use your voltmeter to see if there is a voltage drop from the alternator case to the negative post on the battery. You probably need about three people to do this; one each side of the engine and one to rev the engine to say 3000 to ensure maximum current is flowing. The voltage drop is proportional to the current flowing so you need to be creative; so turn on everything.
The glowing alternator light means the alternator is not generating enough voltage to equal the battery voltage; hence the battery is discharging. It may be generating some current but not enough to cover the loads, so the battery must make up the shortfall. The alternator light is a critical part of the charging circuit, and AFAIK there is no substitute for the original bulb.

[VaccaRabite]

I chased this for weeks over the summer. You have a grounding issue. Search my thread and you can read all the stuff that went into fiding the issue, and all the fantastic troubleshooting advice I got from Spoke and Clay and others.

I fixed it by running a heavy gauge wire from the alternator case to the chassis ground point behind the relay board. It does NOT take much resistance in ground to cause an issue, and the loss of a volt or two is huge.

Zach

I would also feel around the bottom of the VR plug on the relay board to make sure you have not pushed a connector through the tar. I did that too.

[DRPHIL914]

I chased this for weeks over the summer. You have a grounding issue. Search my thread and you can read all the stuff that went into fiding the issue, and all the fantastic troubleshooting advice I got from Spoke and Clay and others.

I fixed it by running a heavy gauge wire from the alternator case to the chassis ground point behind the relay board. It does NOT take much resistance in ground to cause an issue, and the loss of a volt or two is huge.

Zach

I would also feel around the bottom of the VR plug on the relay board to make sure you have not pushed a connector through the tar. I did that too.

I remember seeing your thread. I did check the relay board and this was all rechecked and tested when I was having grounding issue with my fuel pump. Bottom of board is in perfect condition. But I will check ground and voltage as suggested above in the other post, it could be the fan housing is not making a good ground due to the powder coating? I can easily run a ground wire from the alternator case to the chassis and see if that helps. So either the alternator is dying or its not grounding so it cant properly do so. I hope its that simple. you would think a brand new Bosch alternator would not be the cause of this, and that is certainly easier than having to pull the whole alternator out!
I have a new alternator harness in there so I would not suspect this unless a contact or ground is loose.

[VaccaRabite]

If your fan shroud is powder coated, I can promise you that you are adding resistance and that is likely causing your issues. In my case seeing the ohms was difficult as the resistance was small, but it was causing a drop of 1.5 volts.

Run a ground wire. Make sure you also clean (sand or wire brush) the stud just to make sure there is no blockage there. I bet that fixes the issue.

Another thing, different VRs will show different voltage, regardless of what they say they will produce. I have 4 that tested between 13.25 and 14 volts. The one on my car measures about 13.5 volts at the battery.

Zach

[davep]

Here is where I have connected an extra ground cable:

[DRPHIL914]

iam going to do this tomorrow. i just took the car out for a spin, been sitting on battery maintainer for 2 weeks and was at 13.5 or so before starting it ans was at 12.4 running, and tdrove over to the autozone and their tester says 12.4, voltage reulator and or diode failed. i realize its probably not the regulator and probably my ground so an additional ground should do the trick. if not then the alternator will be returned in short order .

[VaccaRabite]

Run the ground wire from the chassis of the alternator (one of the three long bolts that hold the Alt together) to the chassis of the car. I would not use the dog house, as you are already grounding from there in theory, and it isn't working.

There is a chassis ground point just under and forward of the engine bay relay board. Clean it and use that one. It should have ground wires from the engine wire harness attached to it.

Zach