Zener circuit not working as expected

[@rt]

False alarm.. mods please delete.

Transistor was shorted collector to emitter.

[greenpossum]

Even so, you need to calculate the series resistor so that you're running the zener on the slope, not where a little leakage current will turn on the transistor if it has enough gain. A zener is not a perfect threshold switch.

[Zero999]

And a zener probably isn't required in this application, just use a higher value base resistor. The relay is also missing the important flyback diode across the coil, to protect the transistor against the back-EMF, when it turns off.

[JoeyG]

No diode snubber across the coil to protect the transistor???

[@rt]

No, the transistor was out of a junk box and already no good.

My circuit does have the protection diode, caps for the reg, and another diode for reverse polarity protection.