How to Use a Power Probe for Car Electrical Testing

Short answer: to use a power probe, you clip it to the vehicle battery for power and earth, touch the probe tip to the point you want to check, and read voltage, polarity or continuity from the display. It replaces juggling a test lamp and a multimeter with a single one-handed tool — which is exactly why apprentices borrow the boss’s so often.

This is a plain-English walkthrough for anyone using a power-probe style tester for the first time, using the PowerScan PS100 as the example. No prior electrical theory needed.

1. Connect for power

A power probe draws its own power from the circuit it is testing. Clip the supplied leads to the battery — positive and earth — so the tool is live. Because the PS100 runs off the vehicle battery, there is nothing to charge first, and the 6-metre lead gives you room to move around the car from that one connection.

2. Read voltage and polarity

Touch the probe tip to a terminal, fuse or connector. The TFT colour display shows the voltage (anywhere from 0 to 65V) and the polarity — whether you are on a live feed or an earth. This is the fast “is power getting here, and which way round” check that makes up most roadside diagnostics.

3. Check continuity

With the circuit unpowered, use continuity mode to confirm a path is unbroken — ideal for earths, switches and suspect runs. Continuity to 200 kOhm, backed by a tone, means you can confirm a good earth without staring at the screen.

4. Work safely around electronics

Use common sense: never probe the orange high-voltage cabling on hybrids and EVs, and switch to the high-impedance mode around sensitive ECU and signal lines so you are not injecting a load where it matters. The 10A thermal-trip breaker adds a layer of protection during live testing.

Common first jobs

• Confirming a fuse has power both sides.
• Checking a bulb holder is getting a live feed and a good earth — see the car electrical tester guide.
• Testing a relay’s terminals — see how to test a car relay.
• Hunting an overnight battery drain — see the battery drain guide.

Look after the tip

The probe tip is fixed for durability, and the kit includes adapters for different connectors, so match the adapter to the job rather than forcing the tip. Treated sensibly, it is a tool that shrugs off daily workshop use.

Putting the PowerScan PS100 to work

The Autel PowerScan PS100 is a 30 g power probe that draws power from the vehicle battery, so it is ready the moment you clip it on. It reads 0 to 65V and continuity to 200 kOhm on a TFT colour display, shows polarity, has an integrated LED work light and a 10A thermal-trip breaker, and ships with a 6-metre lead plus connector adapters. It covers 12V and 24V systems and has a high-impedance mode for ECU-sensitive lines. It is GBP 212.49 inc. VAT with Free UK Delivery, 30-day returns and a 12-month warranty plus UK support, rated 4.8 out of 5 from 300 reviews.

Frequently asked questions

How do you use a power probe?

Clip its leads to the battery for power and earth, then touch the probe tip to the terminal, fuse or connector you want to check. The display shows voltage and polarity, and continuity mode confirms whether a circuit is unbroken when the power is off.

Does a power probe need its own batteries?

No. A power probe like the PowerScan PS100 draws power from the vehicle's own battery through its leads, so there is nothing to charge before use.

How do I avoid damaging the ECU with a power probe?

Use the high-impedance mode around sensitive ECU and signal lines so you do not inject a load, and never probe the orange high-voltage cabling on hybrids or EVs. Stick to conventional low-voltage circuits.

What can I check with it as a beginner?

Start with simple jobs: whether a fuse has power both sides, whether a bulb holder has a live feed and a good earth, and whether a relay or earth path is intact. These cover most everyday faults.