Electrical Problems


    How it works:  Using the photo below, You can see that adjusting  the 3rd brush connected to the field away from the Armature + will weaken the out put.  The cut out on top of the Generator engages when the generator voltage is greater than the battery and disconnects to prevent discharge.  This can be replaced with a diode.  The light switch controls the Field Resistance.  When you pull the light switch to the first click, it increases the generator output to full. Next click is parking lights and 3rd click is headlights.
   If you set the 3rd brush at full with the cut out the generator will be chugging full out put and may  boil the battery.   If you wish to installed a regulator out of sight, Attach the  Ammeter wire to  "Bat"  terminal, the   Field Resistance wire to the light switch to the "Fld" terminal  and the  wire from to cut out to "Arm" terminal on voltage regulator.  Set the 3rd brush  on full and the regulator will take care if things.    Since the 37 generator only has an 18 Amp output, You may wish to use a newer Generator with greater out put. Adding a regulator will not increase the out put.
    A 50 Watt (sealed beam) incandescent bulb uses more juice than a 32  Watt (original) bulb.  Halogen gives more visible light  per watt.   If your headlight bulbs don't list a wattage, just test it with an ammeter, and do a little math. (Amps X Volts = Watts) If you have Radio, Heater, Fog lights or other Amp eating accessories, your battery will go dead as your stock Generator won't power more than 2 at once.


    Most 1937 Chevrolets rolled off the line with a 6 volt electrical system.  Now a days a 12 Volt is more common and many parts stores won't sell you 6 volt parts.  You may want a 12 volt system for a CB while on tours, a Stereo, AC, or it might be hard starting.  You could buy a converter to boost your 6 volt system to 12 for the CB. The non regulated 6 volt system won't put out enough for your lights, radio and heater on at the same time. If you add a converter to that, you'll have a dead battery for sure.

If you have hard starting problems due to electrical problems, I've addressed that problem below**.    A 12 Volt system was optional for 37 Chevys but they  are few and far between.  See accessory page below:

    The above picture does not accurately depict what is needed  to convert 6 Volts to 12.  A fan blade has nothing to do with voltage.  Note the bottom of the page that the 12 Volt battery cost around $60 where a 6 volt cost only $6.  Also the battery hanger is "to be made locally".   Since this is an alternator, they should have shown the giant rectifier as pictured below.  Today, little diodes replace the rectifier.  (a 1954 picture is all I could find.)  My Flxible bus has a 6 volt alternator and Two - 6 volt batterys in parallel.  


Hard Starting

**If you are experience hard starting problems due to a slow turning starter, be sure to  look at this.    Your 37 Chevy is supposed to have a group 2 battery.  A group 1 and VW battery have less capacity and  have the terminals reversed.  The Positive cable is usually long enough to reach the Starter, but the Negative ground strap is too short to reach the transmission.  The same mechanic who installed the wrong battery,  invariably attaches the ground strap to the frame or replaces with a thinner 12 volt cable.    This seriously reduces the current reaching the starter causing it to crank slower and reduce voltage to coil.
    I know you can understand the thinner cable but the frame seems like a substantial chunk of metal.  Problem is that the engine and transmission are supported by rubber motor mounts. Not much current is going to travel to the rear axle through the springs bushings, bearings, gears, cork gaskets, grease, paper shims, to the starter.  The metal fuel line will turn red hot as will the Choke and Throttle cables.  Make sure that your restoration's paint isn't acting as an insulator.
    Since the batteries in my Electric Vehicle (EV) happened to be 6 Volt and only 2" taller than the group 2.  When replacing the battery hanger, I make sure to make the new one long enough.   When I get a new set of batteries for the EV, the best of the used ones go into the 37 Chevys.
     If it turns fast enough but has trouble kicking,  Check timing.  If spark is weak and your car has been sitting over 6 months, replace the points.  Also, the fuel may have congealed in the line.
    If it hand cranks or bump starts but won't  kick with the starter, look at the wiring diagram below.  Place a volt meter on battery plus and the starter terminal and crank.  If you read more than a half volt, that's a big loss.  Assuming the same loss in the negative cable, your coil is trying to spark a cold engine with less that 3 volts.  (The battery may drop to 4 volts with starter load).  If you run the line from the ammeter to the battery instead of the starter, you'll get more spark.

Wiring & lighting

    Below is the total wiring schematic for your 37 Chevrolet.  Now if you add accessories like radio, CD, tape,  heater, Air Conditioning, turn signals,  electronic fuel injection and ignition module, Anti lock brakes, lighted vanity mirrors, Power windows, retractable seat belt, Rear window defogger, electric wipers, car alarm, cell phone, Cigar lighter (or other stuff plugged into power ports) and hood, trunk, back-up and dash lights to the schematic, you understand why auto manufacturers are thinking of going to a 42 volt system.

     If you have wiring problems, most can be traced to a ground not conducting thru paint or rust.  While rewiring, run a ground to every appliance and Generator and Battery.  For Fuel gauge problems, Click here!       When redoing the taillights, get a 3/4" copper pipe brush at plumbing supplies.  Remove the center contactor (pigtail) and clean socket thoroughly with brush.  Same brush works great on corroded battery cables.  Soldier a ground wire to the side of socket.   Replace pigtail and liberally grease the socket with Chassis lube.  This will give no place for corrosion to form and your lights won't flicker.

    If you're doing your own rewiring, here are suggested gauge wires for 6 volt system.
                                           6 Volt                12 Volt
Battery cables to starter:      1 gauge cable.    2 gauge                     [Ground to transmission.]
Battery to ammeter:            8 or 10 Ga          10 Ga                      [Assume 12 volt users have CD, Stereo, Air Cond, ect.]
Ammeter to Generator:       10 Ga                 10 Ga
Ammeter to headlights:       10 Ga                 12 Ga
Ammeter to Ign Sw:            10 or 12 Ga       10 or 12 Ga
to Coil                                14 Ga                 16 Ga                     [some 12 volt systems have special resistor wire.]
Dome light:                         16 Ga                 18 Ga
Tail light:                          16 or 12  Ga        18 or 14 GA                [single taillight vs 2 taillights and 2 more on trailer.]
Brake light, turn signal:      14 or 12 Ga         16 or 14 Ga              [ ditto but no clearance lights]
Horn:                                 12 Ga                    14 Ga
Radio                            12 or 18 GA                18 GA                    [tube radio vs transistor.  You figure the watts.]
Heater:                               14 Ga                    16 Ga                  [Without AC]

I also recommend running an equal size ground wire to all appliances, Battery, and generator.

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