1939 Electrical Problem

[RC Drown]

Glad that all systems are go.  Now go out and drive the heck out of it, that is what these old Plymouths were meant for:)

[Bill E Bob]

Thanks to everyone for their help. I was able to get a new switch manufactured by Standard Motor Products from Partsource a local auto parts supply & everything is working great. Really appreciate it.

Bill

[plym_46]

If you touch nothig else when you remove the switch, you can take it out, clean it blow out the part where the fluid goe into it, clean off the contacts and re install it without worrying about bleeding the system after it put back in.  There might just a bit of debris in the fluid space that will keep the switch in the closed position (power to the brake lights) some compressed air and or a bit of mechanics wire wiggled around might fix your problem. If not replace the switch, they are generally readily available at shops that deal in motorcycles and or ATV's as thye use the hydraulic switches across many brands of vehicle.

You may also want to check the pressure relief port in the bottom pf the master cylinder reservoir.  If you remove the cap and shine a light into the fluid reservoir that should be two holes visible, a large on to feed the MC piston chamber and a smaller on just in front of it to allow fluid to return whne the pedal is released,  any debris i the relief port will leave some residual pressure in the lines.  Not enough to drag the brakes, but maybe enough to keep the switch closed. 

Also make sure the Reservoir cap's venting is clear.  I would tak a look at the MC situatioin before dealing withthe switch.  If the ports are both clear and the cap is venting properly, then check the switch.

[TodFitch]

On the left frame rail, about 6 inches in front or the master cylinder.  There is a brake line going from the master cylinder to the switch body. The switch  has two wires going to it. Pull the wires off and check the switch with a ohm meter, the switch should be open when the brake pedal is in the relaxed position. I have never changed the switch before, but the switch does remove without changing the body. If you are a novice you might want to have a brake man rebleed your brakes, I don't know if the swich can be removed without air getting into the system. I don't know what is under the switch, don't know if its a open system or closed system.

There is a hole in the bottom of the switch that lets brake fluid into it. I successfully replaced the one on my car without having to rebleed the brakes, not sure if I got lucky or not though.

[MRR41 COUPE]

On the left frame rail, about 6 inches in front or the master cylinder.  There is a brake line going from the master cylinder to the switch body. The switch  has two wires going to it. Pull the wires off and check the switch with a ohm meter, the switch should be open when the brake pedal is in the relaxed position. I have never changed the switch before, but the switch does remove without changing the body. If you are a novice you might want to have a brake man rebleed your brakes, I don't know if the swich can be removed without air getting into the system. I don't know what is under the switch, don't know if its a open system or closed system.

[Bill E Bob]

Thanks to you both for your help. The brakes work fine,so hopefully it is the switch & not a short problem. I'm a real novice at this sort of thing & would appreciate it if either of you could tell me where this switch is located

[MRR41 COUPE]

Do the brakes work properly? If the master cylinder rod lenght was adjusted, the pressure might not release from the system. I agree with the last post, first check your switch, if it's not one of these causes, you have it miswired, or there is a  short somewhere, good luck.

[RC Drown]

Did you check your brake light switch, it could be sticking

[Bill E Bob]

The brake/tail lights on my 39 are staying on & drain the battery - cannot shut them off. Car is 6 volt, & all the wiring was replaced. The previous owner did add a second bulb in the tail lights  & lights in the front with flasher for turn signals which work fine.
Any ideas in solving this strange problem would be appreciated.

Thanks

Bill