sleeton

I have a 71 cutlass with a 350 in it. I just installed a new alternator regulator and now when I turn the key off and pull out the key, the GEN light stays on. It is not fully illuminated but appears to be half as bright as fully illuminated.
What is causing this?

I have attached a picture of the type of gauge I have.

droldsmorland

The bulb is receiving a back feed voltage. Usually, the reg or the bridge diode in the alt are allowing this voltage to leak when it shouldn't. Try turning on the headlights with the high beams on, engine off. Does the light go out? Did you hear a "ting" sound from the regulator?
If the light goes out and you hear that noise its a bad regulator(most likely). Purchase a solid state regulator. Keep the Delco cover off the original. It can be put on the new reg for that OEM look. Make sure all grounds are shiny and tight. Let us know as there are a few other things to check. Whats the charging voltage when it's running?
Remember new doesn't mean good. especially with the influx of offshore junk today.

sleeton

Thanks I will try that, one thing I have heard is that when I reconnect the battery as I disconnect it each time I start the car is that ting noise you spoke of coming from the reg. Also, I bought a reg from NAPA as I have heard they seem to have better quality parts and I did buy the best one NAPA carried. I will try your other tests and see what happens. when the engine is running the charging appears to be 13+ volts.

oldcutlass

If you go to a solid state regulator use a Wells VR715.

sleeton

where do I get one of those at

oldcutlass

Autozone sells them under the Wells pn, others auto parts stores may use another. You can bolt your stock cover to it.

sleeton

droldsmorland,

I turned on the headlights with the high beams on without turning on the engine and the regulator did not "ting" and I also replaced the battery cable that goes from the negative post on the battery to the mounting bracket of the alternator as the cable had a large gash in the protective covering but this too did not change anything.

What should I try next

Thanks

droldsmorland

The negative cable should be attached to the driver's side head up front, not the alt bracket. A shallow bolt/star washer secures it to a threaded hole under the alt in the front surface of the head. There should be a ground strap from that same head to the firewall on the rear of the head. The fasteners, washers, and strap are reproduced.

First test the alternator output with a voltmeter. It should be about 14.2vcd +/- .5 engine running. If not remove the alternator and have it tested by a shop that rebuilds alternators. Tell the shop you are getting feedback to the light on the dash. New doesn't mean good. Take the regulator with you too. They can test both as a system.

sleeton

Droldsmorland

I went and looked at my car today and I do not see a ground strap from the back of the head to the firewall. I wonder if this is my problem as I understand it that would mean it is not grounded.

oldcutlass

While you do need a ground from the engine to the firewall, you can see if it makes a difference by fabricating a temp ground with a 10ga wire.

joe_padavano

The fact that both your GEN and BRAKE lights stay on hint that there might be a common problem with that gauge pod, circuit board, or harness.

droldsmorland

Sleeton,
What is the surface charge on your battery? What is the running voltage with and without ALL of the lights on?

With the engine running and the bulb glowing dimly, you have a voltage drop on one side of the bulb. Having the same voltage on both sides of the gauge bulb is correct and the bulb should not illuminate. If one side or the other shows a drop the bulb will start to illuminate. The greater the difference the brighter the bulb illuminates up to full system VDC.

That said a dim glow points towards a voltage drop on one side of the bulb. Find which side the drop is on by probing the 2 bulb conductors at the gauge pod. This will lead you in the direction you need to troubleshoot.


Yours has an external regulator (correct?) and the light is fed from the regulator connector on the firewall terminal #4, I think it's a brown wire. The brown wire goes through the bulkhead connector and then directly to the light. On the other side is a pink wire that also feeds power to your fuel gauge, temp light, parking brake light, and oil pressure light. So depending on which side of the light is low (brown or pink wire to ground) that will point you to which direction you need to go.

Now, the above is for a running dim light situation. Yours illuminates with the key off which to me points to a bad bridge in the alternator or a sticking contact set in the analog VR (provided the voltage readings I asked for above are normal).

Poor grounds will affect this too. So start simple by checking all grounds and adding any missing ones. Then go into the charging system.

sleeton

Joe,

I do not believe the GEN light came on until after I replaced the regulator. I replaced the regulator as the battery was not getting charged. The battery before going into the car read about 12.2 volts and once the battery was in the car with the car running, the volts read 13.2

droldsmorland

13.2 VDC is too low. Which is probably why the light is illuminated...it's doing its job telling you your charge voltage is below spec(low). It should be 13.8 to 14.2VDC to be within typical spec for a car from this era.
An analog (mechanical) VR (volt regulator) has adjustment but only in the hands of a well-versed mechanic. I'd suggest you invest in a solid state VR. Then verify the output voltage is within 13.8-14.2 VDC.

droldsmorland

To recap:
You have installed a new voltage regulator AND a new alternator, correct? Why did you do this?
Have to make sure we're seeing the whole picture here before we go any further.