Pre-war (up to 1942) Amperage when adding inline fuses to 1936 Cadillac

[Dennis Rizzuto Jr]

Amperage, 1936 Cadillac: I'm going to add some inline fuses and a fuse block to my wiring. Has anyone done this and if so, does anyone know the correct amperage for systems such as the headlight, radio, etc.? Is there anywhere I can find this info? Any help would be great. Thank you, Dennis

[V63]

The headlight switch is protected internally. The radio is typically 10-15 amp. The factory service manual shoukd have specifics. The factory used metal fuse holders and cloth wrapped wires which is a perfect storm for problem at this age.

I would buy something like this and mount under the dash, it has 10 possible circuits and uses more readily available fuses plus the circuit glows when a fuse is blown.

It reads 12v but the protection and the LED will be fine with 6 volt, remember that the LED are polarity sensitive.

[Dennis Rizzuto Jr]

Thank you very much, just the info I was looking for.

[Chopper1942]

This is probably more than what you want or maybe need, but this is how I would approach updating an electrical system on an older car.

These are the circuits that are fused and the fuses used on a 51 Caddy:
Deluxe heater - 30 amp
Standard heater - 30 amp
heater - 14 amp on heater switch
defroster - 14 amp on defroster switch
Radio - 14 amp
Turn signals - 9 amp
Spot light - 14 amps
Horn - 14 amp

Many of the older vehicles had a circuit breaker in the headlight switch to protect all the lights. The problem is that if a B+ (hot wire) from the headlight switch shorts to ground, all the lights will go out and/or flash on and off. The better way to do the lighting system is to fuse each headlight, tail light/park light, brake light,and instrument panel light with their own fuses. This way if for example, the right tail light hot wire is pinched and shorts to ground, it only blows the fuse for the right tail light and you don't possibly lose all the lights on the rear.

Unless you are trying to keep the car original, I would rewire the car with new wire. Use the same gauge as the original wire.

I would definately install an updated fuse block that is wired directly to the battery. I also like to install a kill switch in the positive battery cable. This allows you to shut off all power to the vehicle when you let it set for an extended period of time.

When you add an auxillary fuse panel, there are several other circuits tha need fused. When I rewire an older vehicle, I wire them with same circuit protection as used on modern vehicles and follow the GM color coding for the circuits.

Reroute the original fused circuits to the new fuse panel and add the following circuits.

Park & tail lights - brown
Rt front turn signals - Dark Blue/white
Lf front turn signals - lt blue/white
Rt rear turn signal/brake light - Dark green
Lf rear turn signal/brake light - Yellow
tail lights & license plate light - brown
Lf high beam - Dark green/white
Rt high beam - Light green/black
Lf low beam - yellow
Rt low beam - tan

All ground circuits are black and B+ are usually red or orange.

Some of the wires have a white or black tracer, but for a rewire, you could use solid colors if the white and black tracer wire is no available.

If you do rewire or install an aux fuse panel, make a notebook with the wiring schematic of the changes, the wire colors, and fuse size for each circuit.  This would be a good idea for future diagnostics if needed.



If it is too difficult to run wires for separate circuit to the rear, at least have the tail lights and brake lights on their own circuits. Do the same for the high and low beam circuits for the headlights.


If you don't want to run wire, you can install weather proof inline fuse for each circuit. For example: for the tail lights, I would cut the tail light circuit wire from the headlight switch and connect that wire from the headlignt switch to the aux fuse panel. Then splice in a new wire from the aux fuse panel to the old wire going to the tail lights. Then, I would install an inline fuse holder with a fuse smaller than the one in the fuse panel. This way if the main feed wire shorts, the fuse in the aux panel will blow, but if one of the feed wires down stream of the inline fuse shorts to ground, you only loose the one tail light.

For all splices and terminations use weatherproof heat shrink crimp butt connectors and terminals.

[Dennis Rizzuto Jr]

Thank you very much, great info covering all the bases.

[bcroe]

If those old cars used positive ground, I would
not expect any LED indicators to work.  Keep in
mind circuits might be categorized as ignition
switch powered, accessory position powered, and
continuously powered.  Each of these groups must
have their own common feed point.  Bruce Roe