The Stovebolt Site Forums The Shop Area The Electrical Bay identifying a 6v generator

The generator on my 1947 truck is still 6v. Last night I think it turned its last turn until I get it rebuilt. I have another generator off of my 1950 chevy coupe that has the splash system 235. The difference I notice right away is that the coupe generator has an external condenser held on where the ground screw is and a wire lead that reaches to the armature post. Can anyone tell me if this generator is 6v by my description?

The condenser is to reduce radio noise. It has nothing to do with voltage. Is the tag the same color on both?

No tag

The condenser was added to reduce the RFI in radio equipped vehicles. You can keep it on or remove it, doesn't matter as far as chargeing goes.

re. determineing what voltage the gen is.

Secure the gen in a vice. Ground the F (field) terminal.
Hookup your VOM with the negative lead on the grounded F term and the positive lead on the A (armature) term.
If you spin the pulley by hand you should see 1 to 2 volts. This will tell you that it can produce a voltage.

Take an impact wrench or drill or anything that can turn the gen rapidly, using a socket on the pulley nut spin the gen over as fast as the tool will spin it.
If the gen is producing voltage it will "resist" the power tools spinning motion and try to slow it down. This is good as it won't allow you to over spin it and it also indicates that your spinning it in the right direction.

Check the voltage while it's spinning. The gen will output approx double the desired regulated voltage, i.e. a 6v gen will make between 12 - 14 volts, a 12v gen will make between 24 - 28 volts.
14 volts or less = 6v, 24 and above = 12v.
Good luck
Dave

I had one generator that had 6v stamped on it. That made it easier.

Was 1950 still 6v?

Chevrolet truck - 6v negative ground through 1955-1st series

GMC - 6v positive ground through 1955 (I think that Blue Chip 1955 GMCs had an optional 12v positive ground battery).

It is a 6v. Thanks.

I would suggest that you remove an old condenser if it is on the generator. They can and do go bad and that usually means a short.

I did remove the condenser. Thanks for the tip about the short I never thought of that.

I took the generator apart to clean it up and check the brushes. Brushes seemed to be in good condition. The part that the brushes ride on, sorry I am not too knowledgeable yet, was black so I cleaned it up back to the copper color it should be. Reinstalled the brushes. Reassembled the generator. Put it on the truck and started up no problem. I even seen my headlights get brighter with the increased acceleration from idle. Drove around yesterday without problems. Went to go on a drive today and nothing. Dead battery. Any advice where to check and what to look for? I have a volt meter but not too sure how to accurately use it.

When I put the leads from the voltmeter to the generator I get a reading of 7.1 to 7.2

At the voltage regulator i have 6.9

I have the voltmeter set on dc and it it an innova 3300 model

My battery shows 6.5

I jump started my truck and drove 33 miles. I turned it off to get gas and no juice to restart. The battery had 5.5 on the voltmeter now after the drive. No idea what's going on.

sounds like the system is working, might be worth getting the battery tested, could be bad

Bill

Would the battery not get recharged from the generator as its running?

When some batteries go bad they won't start the truck after a running charge but will start it after cooling off. I'd get the battery checked.

The autozone I am at said it was dead when he checked it so he is charging it now. I have to wait until tomorrow at the earliest before I can replace it. Thank you all for the help.

While it is running it drives fine. I even got up to 63 mph on a 50 mph road keeping up with traffic.

Battery charged and tested good

Got home pulled the positive cable off and the engine continued to run

it should continue to run, the generator is supplying power, so you know that's good .... OTOH, not sure I'd trust Autozone to do a proper load test unless you stand there and watch

Bill

I still have the same issue so something must be wrong. It seems everywhere I have at least 6 volts except at the field terminal at the generator. Should there be voltage coming off the field post of the generator?

Short answer is no. The regulator grounds the field terminal inorder to complete the circuit and make the generator make voltage.

I just recenty went through troubleshooting my 6v system and I'll pass along what I found out. keep in mind this applies to a 49 3100.

1) There should always be battery voltage on the reg's "Bat" term.
2) The reg's "gen" term connects to the gens "bat" or "arm" term. It should be a home run wire. Make usre theres continuity on the wire between the gen & reg.
3) The reg's "field" term connects to the gens "field" term. Make sure the home run wire has continuity.

1st read the battery voltage, this is your reference mark.
To test the gen, connect up a voltmeter on the gen's "Arm" term.
Start the engine and observe the volt reading. Should be atleast bat voltage. increase rpm and the voltage should rise to 7 or more volts.
Now connect the meters pos lead to the reg's "gen" term and repeat test. should be the same as before. If not theres a wireing problem between the reg & gen.

IF you get no voltage or low voltage, make up a jumper and with the volt meter connected as before temporarily ground the gens "field" term and increase rpm. YOu should see atleast 7 volts.
If not the gen is not producing voltage and needs rebuilt.
If you do get voltage, move the meters pos lead to the regs "Bat" term and repeat, the test should read the same, if not theres a wireing problem betwwen the reg & gen.

The reg has 3 relays. from right to left (when seated in the cab) the 1st is the cutoff relay. It provids the connection between the battery & gen. It is open when the gen isn't producing voltage to kepp the battery form dischargeing back through the gen. It closes when the gen's output voltage is higher than the battery voltage.

The 2nd relay controls the voltage produced by the gen. It has 2 windings that work against each other to control the voltage.

The 3rd relay controls the current flow by controlling the ground being applied to the gen's field term.

If the battery is dischargeing it could be in the reg, the cutout relay could be sticking closed. You can pull the cover and depress the relay contact down. if it moves down it was sticking in the up "make" position, which will discharge the battery. beaware that theres voltage on those contacts so be carefull. You could burn something up.

I haven't read the whole thread but it seems you need to determine if the battery is dischargeing when the engine is off.
This is a simple test. You need a tail lamp or running lamp bulb.
solder 2 leads to it. one lead to the soldered tip of the bulb and solder the other lead to the bulb's metal case. place one lead on battery pos and the other on battery neg and it should glow. this will test that you've wired it right.

Now disconnect the battery's pos terminal and clamp or wrap one of the test bulbs leads to it. Connet or wrap the other test bulb lead to the batterys pos terminal. If the lamp glows you have something drawing power when it shouldn't be.
If the lamp doesn't glow either turn the ign switch on or pull the lights on to make sure you have connected correctly. The lamp should then glow and power will supplied to the device you turned on.
If the lamp passes the tests but isn't on w/everything off you don't have anything pulling power when the engine is off.
Beaware that a small draw, will still pull a battery down and a small draw will barely light the lamp under test.
Good luck
Dave

At idle I checked every place where power should be. This is what I got

Generator
At armature..... 7.25
At field........ 0

Voltage regulator
At armature..... 6.9
At field........ 1
At power........ 6.9

Coil
At +............ 6.2
At -............ 3.5

Starter........... 6.8

Battery........... 6.77

This morning I try to start it. No noise after I stomp on the starter button with key on or off. I checked the battery with voltmeter it says 6.19 volts
Checked the volt reg and it says 6.19 DCV
But won't start. Jump start it and it's fine.

Sounds like a battery problem, may have good volts but no cranking amps.

After the battery was recharged from autozone I was able to start the truck fine 5 or 6 different times before the last time I needed to jump start it. I am about to drop it off at a shop and have them tell me what's going on.

I brought it to a shop and they said the voltage regulator was not working correctly. I swapped it out and got a 6v optima. Problem solved until the optima dies.

Glad to hear you got it fixed! FYI it's a whopping 3 degrees here!!

Optima battery died and I stuck it on a charger yesterday after helping a friend move on saturday. I grabbed an old Delco Remy voltage regulator i had in a junk pile in my back yard and put it on. No idea how many times it had been rained on and dropped and oil spilled on it, but it's working.