1957 Parking Brake Alarm Light

[Dan Wichlan]

Since the correct circuit for my 1957 parking brake alarm light is hot when the ignition is turned off, can I safely use the circuit for my heater which is dead when the ignition is off but which has a higher rated fuse?

[John H.]

Re: 1957 Parking Brake Alarm Light

Dan -

All '57 accessories (heater, radio, park brake light) are fed through individual fuses from a common bus on the accessory fuse block, and that bus (along the bottom of the panel, below the fuses) is hot all the time, fed by a red wire from the center terminal of the horn relay that plugs into a spade on the outboard end of the bus. The input side of all of those fuses (connected to the bus) should be hot all the time.

[Dan Wichlan]

Re: 1957 Parking Brake Alarm Light

Since this circuit is hot all of the time, the parking brake alarm light, which is attached to the spade on the corresponding fuse, flashes even when the ignition is off. This is obviously problematical. It should flash only when the brake is applied and the ignition is on.

[John H.]

Re: 1957 Parking Brake Alarm Light

Dan -

You're right - the lamp grounds through the flasher unit on the park brake, and should only operate with the ignition on. I don't have my '57 any more to check it, but that feed (to the accessory fuse panel) must be fed from the ignition switch, although the circuit diagram clearly shows it fed from the battery terminal on the horn relay (with a branch feed from the battery terminal on the voltage regulator). Must be an error in the circuit diagram, as everything fed from that panel (park brake lamp, radio, heater) should only operate with the ignition switch in the "On" or "Accessory" position.

[Dan Wichlan]

Re: 1957 Parking Brake Alarm Light

The light flashes when the ignition is off and the brake is applied. Why wouldn't this be the case, as long as the circuit is hot when the ignition is off?

[John H.]

Re: 1957 Parking Brake Alarm Light

That shows that the flasher and bulb are working, but it'll run the battery flat if it flashes with the ignition off; it needs an ignition-switched feed so it only operates with the brake applied and the ignition "on".

[Dan Wichlan]

Re: 1957 Parking Brake Alarm Light

John,

That's the problem. The AIM shows the hot lead going to the spade on the alarm light fuse. So the light and the fuse block are properly wired, but I need an alternative. My heater circuit wiring has been altered so that it is dead when the ignition is off. Can I safely use this circuit for the alarm light even though it has a higher rated fuse? Thanks.

Dan

[John H.]

Re: 1957 Parking Brake Alarm Light

Shouldn't be a problem - the heater fuse is 14 amps, and it doesn't draw anywhere near that unless the blower is on "high" speed.