GEN light staying on when key is off

[FarmerPete]

Hello everyone. I have a '57. I took it for a drive tonight and it ran fine. When I parked it in the garage and turned the key off, the GEN light remained on. I restarted the engine and then shut it off, and both the GEN and the OIL light stayed on. I restarted the engine a second time and then shut it off, and only the GEN light remained on. I popped the hood and heard a buzzing noise coming from the generator, and the generator was smoking. I disconnected the battery for a few minutes and then reconnected it. Both the GEN and the OIL lights stayed off. I did not try to restart the car. The car still has the generator and external regulator. The regulator is new.

Any suggestions?

[Fnixon]

To me it sounds like the cutout relay points failed to open and I would think the new regulator is bad. You may have a damaged generator now.

Here is a further explanation that I think will explain what you observed. When the engine stops, the points in the ignition will either be open or closed. When it stops with the points open, the GEN light is powered from the stuck cutout relay in the regulator and the current flows down through the light and through the oil pressure warning light. Thus yo see both lights on. However, when the points are closed, the current goes through the GEN light and down through the coil, through the points to ground. Because the GEN light has a very high impedance, the voltage at the coil is very small and the oil pressure light does not light up.

[droptopford]

Thanks Fnixon! (This site really could use a 'Thanks' button) I think your explanation makes sense. And the fact that the regulator is new casts even more suspicion in that direction. So many new replacement parts are just not up to OEM quality.

So to help me understand this better (I'm no electrician)... With the regulator relay points stuck closed, would the current be flowing (backwards) through the brushes to the armature and causing the windings to smoke? Thanks.

[Fnixon]

The brushes and armature normally operated with the coils energized for very short periods of time and they are producing a counter EMF. So in one sense one could say that the current is flowing in reverse. With regards to the regulator, I know with GM products, I don't use anything but the old originals. I test them out on my bench and collect a stock of good ones. The aftermarket GM regulators are mostly really bad.

[FarmerPete]

Thanks Fnixon. Your explanation makes a lot of sense.

To give you an update, I replaced the generator with a higher amp alternator from Powermaster. The alternator has a built-in regulator, so I removed the regulator. The alternator is essentially 2 wires. An 8 gauge power wire from the alternator to the battery (technically to the battery side of the starter solenoid) and the ground wire. Actually, I have two ground wires. I used the original ground wire (which is connected to the negative terminal on the alternator and the original ground point near the regulator) and I added an 8 gauge ground wire between one of the alternator's mounting bolts and a bolt on the engine block (same bolt as the battery ground). I have not connected the generator light to the alternator, only because I don't know which wire connects to the generator light. But, the oil pressure light is still on with the ignition in the off position. So power is still somehow backfeeding into the dash area. I though maybe it was the horn relay, so I disconnected the power line between the solenoid and the the horn relay, but the oil light is still on.

Any thoughts on what could be the cause of the backfeeding? Could the ignition switch be bad?

[Fnixon]

Wow this is getting interesting. I am going to go away and think about this. I don't think that you will be able to use your generator light but the alternator supplier may have some suggestions for you. Most people install a volt meter to monitor the operation of the alternator.

[Fnixon]

I was browsing on Ebay and found a variety of alternator charging warning LEDs that turn red yellow or green depending on the voltage. I think that would be a really nice replacement for the old charging light but you would mount it somewhere else. I was looking at this because I just purchased a 1957 Skyliner that was restored and they installed an alternator. I think it may have a small voltmeter but I am not sure. It will be delivered to my house in a few weeks.

[oldave57]

From what I can gather on the Powermaster alternator wiring diagram, the alternator is essentially a GM 1-wire hookup. The only ground connection you need is from the alternator housing to either the engine block or a combination of engine block and body/battery ground. I don't think the original ground wire (connected to the negative terminal on the alternator to the ground location at the voltage regulator) was included in the wiring diagram. I would suggest (for trial) that you disconnect the wire from the "negative terminal" of the alternator and then run the car again to see if the lights act correctly. You should not have any battery indicator light but should have the oil pressure indicator working correctly. You should also check battery voltage with the engine running to see if the alternator is working with this hookup. If this solves the indicator problem and the alternator is still putting out voltage (you might have to increase idle temporarily to "start" the alternator) then you will have some idea if this helps.

Good Luck,
Dave

[December15,58]

I recently performed a generator to alternator conversion using a Powermaster alternator. My original dash generator light works with this swap. I removed the voltage regulator and wired the whole deal after I watched a VERY imformative video on YouTube. The video is by Moss Motors, Ltd. You can find it under the title "Generator to alternator conversion". The video is 10 years old, has multiple wiring diagrams, and easy to understand dialogue instructions to make the swap wiithout a hitch. My 59 Skyliner has a 390FE, so I had to do some research on picking the correct alternator bracket. I found a company in Illinois that produces a quality bracket. There are different ones for FE engines up to 1963 I believe, and others for later model blocks. My block date code shows a C5, so it's a 1965. You need to be certain on which block you have. I also installed a 3 gauge panel which includes a voltage meter. The alternator puts out 13 to 14 volts, and makes the top operation work smoother. Just to be clear, there is one large gage wire that goes from the alternator positive to the fender mounted solenoid, a ground wire from the ground lug on the alternator to the engine block, and a wire that runs from one of the small terminals on the back of the alternator up to the gererator light on the dash. I would have to double check which small terminal is the one for the generator light. It is important to only use the correct terminal. Hope this helps anyone who may be thiinking about doing this swap. Paul

[December15,58]

Updated information on the alternator swap. I looked through my notes, and I actually installed a Tuff Stuff alternator #7127, which has a matt black finish. As far as which terminal is the one to connect the dash gen light, looking from the rear, it is the left hand terminal, marked #1R. Paul

[Fnixon]

I don't want to complicate this thread too much but, I received my charging/battery voltage indicator LED , and it is just want I wanted. If the static battery voltage is really low, it will show red. If it is slightly down it will show yellow and once the charging system provides a proper voltage, it registers green. It has other features to monitor extreme high voltages etc. Since I have taken delivery of my 1957 Skyliner, and it is outfitted with an alternator with no charging light indicator, I am going to install this in the dahs, in it's place.

[Fnixon]

I want to update this post. I found out that my Skyliner does have a GEN light. I believe it has a Motorcraft 3G alternator. Doing some research I now believe that these alternators used in original equipment configurations used a 500 ohm resistor in parallel with the bulb. This ignition feed through the bulb initially energizes the alternator upon startup. Without the resistor, when the bulb burns out, the alternator will not function. This could be very nasty on a trip away from home. Therefore I am planning to add the resistor.