# TopDiag P100 Automotive Circuit Tester

The TopDiag P100 automotive circuit tester combines DC and AC voltage, resistance, and tone modes for diagnosing vehicle electrical circuits. Its claimed 40-foot total cable reach is intended to help access wiring farther from the vehicle battery, though customer feedback is mixed on cable quality and durability.

- [Original product page](https://best-deals.pro/product/topdiag-p100-automotive-circuit-tester)
- [View offer](https://best-deals.pro/visit/topdiag-p100-automotive-circuit-tester)
- Market: US
- Language: en-US
- Currency: USD
- Brand: TopDiag
- Model: P100
- Category: Cars & Motorcycles > Vehicle Diagnostic Equipment
- Price: 46.74 USD
- Previous price: 54.99 USD
- Discount: 15%
- Price checked: 2026-11-14T19:18:49.108Z
- Rating: 4.6 / 5
- Reviews: 680

Prices and deal status are the latest recorded data, not a guarantee of availability. Confirm the price and availability with the store.

## At a glance

- Four modes cover DC voltage, AC voltage, resistance, and tone-based circuit checks.
- The listing describes component activation for vehicle electrical parts such as motors, lights, and fans.
- Short-circuit protection is claimed, with an internal circuit breaker that trips if overloaded.
- A built-in flashlight is described for use in dim work areas.

## Pros

- The listed modes give buyers more than a basic test light, including AC voltage and resistance readings.
- The claimed 40-foot cable reach may help with troubleshooting wiring toward the rear of a truck or trailer.
- The listing describes component activation as an aid to checking individual electrical parts.

## Cons

- Customer feedback includes reports of the tester breaking after limited use, so durability is a reported concern.
- Cable quality receives mixed customer feedback.

## Specifications

### Identity
- Brand: TopDiag
- Model: P100
### Power and battery
- Power configuration: Battery Powered
### Dimensions and installation
- Dimensions listed: 6 x 2.4 x 1.2 inches
- Weight listed: 1.9 pounds
### Testing and compatibility
- Working modes: DC Voltage, AC Voltage, Resistance, Tone On/ Off
- Voltage input range: 9V to 70V
- Supported vehicle types: Vehicles \(12V cars, 24V trucks, trailers\) and their electrical components

## Before you buy

- Cable length is inconsistent across the listing: the title claims 40 feet, while feature text describes a 20-foot tester cable plus a 20-foot extension. Confirm the exact cable arrangement for the selected listing.

## In the box

- 1 P100 tester (Included)

## A good fit for

- DIY vehicle owners tracing electrical faults in 12V cars or 24V trucks.
- Technicians and enthusiasts who want voltage, resistance, tone, and component-activation functions in one probe-style tester.
- Buyers who need to reach wiring along a trailer or toward the rear of a vehicle.

## Less suited to

- Buyers who need a tool with consistently dependable durability, given the reported breakage concerns.
- Anyone seeking a general-purpose household electrical tester rather than a vehicle circuit tester.

## Customer feedback

Customer feedback describes the tester as easy to use and useful, with positive comments about quality and value and mention of its AC and DC options. Durability and cable quality are less consistent, including reports of failure after two uses. For buyers using its listed voltage and resistance modes on vehicle wiring, those concerns matter when weighing a multi-mode feature set against expected long-term reliability.
- Positive themes: Customers describe it as easy to use and appreciate its functionality and value.
- Negative themes: Some customer reports describe the tester breaking after two uses.
- Mixed feedback: Cable quality receives mixed feedback, and durability comments are not uniformly positive.

## Frequently asked questions

### What kinds of tests does the TopDiag P100 list?
The listing names DC voltage, AC voltage, resistance, and tone on/off modes. It also describes component activation for vehicle electrical parts.
### What vehicles is it listed for?
The compatibility details name 12V cars, 24V trucks, trailers, and their electrical components.
### How long is the cable?
The title claims a 40-foot cable, while the feature description specifies a 20-foot cable plus a 20-foot extension. Check the selected listing for the cable arrangement.
### Does the listing describe overload protection?
Yes. It claims short-circuit protection and says an internal circuit breaker trips if overloaded. This is a listing claim, not an independently verified performance result.

## Alternative options

- [Autel PowerScan Automotive Circuit Tester, 12-24V Power Circuit Probe Tool \| Electrical Short Open Breaker Finder, AC/DC Voltage Current Resistance Detection, Trailer Light Test, 20FT Extension Cord](https://best-deals.pro/visit/topdiag-p100-automotive-circuit-tester)
- [Autel PowerScan PS100 Circuit Tester 2.0, 12-24V Power Circuit Probe Tool \| 2026 Electrical Open Short Breaker Finder Tool, AC/DC Voltage Current Relay Resistance Check, Trailer Light Test, 40FT Cable](https://best-deals.pro/visit/topdiag-p100-automotive-circuit-tester)
- [VIDENT 12V 24V Car Battery Tester, 100-2000 CCA Battery Load Tester for Car \| Alternator Tester, Car Battery Tools with Cranking & Charging Lead-Acid Battery for Motorcycle Truck RV Boat ATV](https://best-deals.pro/visit/topdiag-p100-automotive-circuit-tester)
- [BT139 Car Battery Tester & Load Tester for 6V 12V 24V Vehicles \| 100-2000 CCA Analy...](https://best-deals.pro/visit/topdiag-p100-automotive-circuit-tester)
- [Autel PowerScan PS100 Power Circuit Probe Tester, Breaker Finder, 12V 24V \| Automotive Electrical Diagnostic Tool, 20ft Extension Cable, AVOmeter, Test Light, Continuity & Breaker Test, Fits 99% Cars](https://best-deals.pro/visit/autel-powerscan-ps100-mbdh-automotive-circuit-tester)
- [Autel PowerScan 12-24V Car Circuit Tester, Power Probe, Short/Open Finder \| 40FT Extension Cable, Component Activation, Relay & Fuse Test, AC/DC Voltage Test, Resistance Measurement, Duty Cycle Test](https://best-deals.pro/visit/topdiag-p100-automotive-circuit-tester)
- [Autel PowerScan PS100 Power Circuit Probe Tool, Automotive Circuit Tester, 12V 24V Automotive Electrical Tester, Circuit Breaker Finder, AC/DC/Continuity/Signal Test, Component Activation 40ft Cable](https://best-deals.pro/visit/topdiag-p100-automotive-circuit-tester)
- [Autel PowerScan PS100 Power Circuit Probe Kit, 2026 for All 12V 24V Cars \| Automotive Relay Tester Wire Tracer Test Light, Breaker Short Finder Multimeter, Ground Check Activate Component, 40ft Cable](https://best-deals.pro/visit/topdiag-p100-automotive-circuit-tester)
- [ANCEL PB100 Automotive Circuit Tester, 12-24V Power Circuit Probe Tool \| Electrical Short Open Breaker Finder, Component Activation, AC/DC Voltage Resistance Diode, Trailer Light Test, 40FT Cord](https://best-deals.pro/visit/topdiag-p100-automotive-circuit-tester)
- [V200 Pro Automotive Circuit Tester, 12-24V Power Circuit Probe Tester, Electrical S...](https://best-deals.pro/visit/topdiag-p100-automotive-circuit-tester)
- [Wire Tracer VDIAGTOOL V210 Automotive Circuit Tester, Open & Short Circuit Finder C...](https://best-deals.pro/visit/vdiagtool-v210-automotive-wire-tracer)
- [TOPDON CT100 Automotive Circuit Tester with Load Test，3.3-65V Test Light \| Professional Load Test, Digital Voltage Tester, Auto Polarity ID, Audio-Visual Alerts, 150" Spring Wire](https://best-deals.pro/visit/topdiag-p100-automotive-circuit-tester)

## Images

![TopDiag P100 Automotive Circuit Tester — 1](https://best-deals.pro/i/AtWVzxt8LhBIrNRgdTbg6_3U0Z72QFCiGc5KWIww2McQrtyr9ZlwcbbPFPj421nRCG-RMopEgoWqKxl1JD7yltvjAOnfBXvFowRAdzO-tbYSPlSuiYYS.jpg)

![TopDiag P100 Automotive Circuit Tester — 2](https://best-deals.pro/i/PyuhmU6m9Tj5hwXGEtNG17-dpTuHm1Qc0wKHkdNAZDxPL9U5sJWXeQM-fr6m0thBMyHre_KQQEeDfpzXqPsQBFhPNuy5V5usoLFWhNWLzzABirM-6VYY.jpg)

![TopDiag P100 Automotive Circuit Tester — 3](https://best-deals.pro/i/oJwHdeDrTX1YO8MDPHUF7GlLUUgDJyFgbBtwNaZjxRE5xZik4TE3tacv7HWR-WIA2am55vN9CVm6DSoPH1tyXDk1AQIsdXQOqQDVQVRn1iFjWhaYV0D8.jpg)

![TopDiag P100 Automotive Circuit Tester — 4](https://best-deals.pro/i/GLFiqbk4oHlk_Uk3ran1yiIfglzoqk7jHmKBQ3FO5j7iTVz7dF-HN3fZE4RVgAj9cqLdR2uFAcy2ImDAZWaLQx4N8d4TJafEClMsVoqgav49JIfvLiPL.jpg)

![TopDiag P100 Automotive Circuit Tester — 5](https://best-deals.pro/i/mv44Eq35DMcY6LbmPI7y7Y6wh5NmogWO_CWQgyybm9uFq4ZfdYs-cP1WBSM1rFvsTS3-l3MeH0KMkZOnJp0dICyDohbIqGZclY4Uq6VxijnzDJQZGVKb.jpg)

![TopDiag P100 Automotive Circuit Tester — 6](https://best-deals.pro/i/b-Fu3NFNhQ1Cpc5dAOZhIiO899T-XaxkV_glAQQQHaQWq2IfZISyUNE3DhClvrqBNAZrQJwD6KRc2o_3GnwzkKmQul87kJSoEcvSWxH6ce7dn4MVVAcM.jpg)

![TopDiag P100 Automotive Circuit Tester — 7](https://best-deals.pro/i/OYxuK-7RPzBJGvNavCwCTYWNsXWz0KfvRjZMT83ROXUliMoi0SM4wCSQiJ7jYQNWBYyXQs-rkPD2vPpI55oJMhNbkji7Z_V1SGcN7bfwKaQnqmFnUZZ0.jpg)