Make sure your electrolyzer is connected to a good power source.
12 volt accessories are fine, i.e., the windshield wiper motor, the daytime running lights, etc. Or you can use an auxiliary fuse in your fuse box (usually) under the hood.
MAKE SURE YOUR ELECTRICAL SOURCE IS 12 VOLTS AND ONLY COMES ON WHEN THE IGNITION IS IN THE "ON" POSITION, #2. Remember that you should never leave the key on for any length of time without the engine running. This will fill the manifold with hydrogen, which can explode when you start the car.
Better: use a cheap vacuum switch in your output hose. Connect this to a relay, which then powers your unit. This means the unit is on ONLY WHEN THERE'S VACUUM. That means only when the car is running. This is the safest electrical connection.
The following article will give you more details, part numbers/prices and connection diagrams:
PROBLEM: I never forget to turn off the ignition switch. However, a couple of readers have forgotten to switch off the power (the Electrolyzer was on all night), and either caused a small explosion when the engine was turned on - or have drained the battery.
SOLUTION: The next diagram shows an optional electrical connection, preventing Electrolyzer operation unless the engine is on:
This arrangement is good only if you have vacuum, which means:
Question: What to do if you don't have vacuum?
Answer: replace the vacuum switch with an automotive OIL PRESSURE SWITCH. This type of switch should cost a few dollars only. If you Google "oil pressure switch" with your vehicle's model, you will find them starting at about $1-$3 and up. However, such a switch should ONLY be connected to the engine by an experienced mechanic, to prevent risk of leak or losing oil pressure. Then, you can follow up and complete the electrical connection yourself, per the diagram below: