The Klein Tools RT390 is a professional-grade circuit analyzer for North American 120V AC three-wire outlets. It identifies wiring faults, inspects both AFCI and GFCI devices with trip time and trip current measurements, displays live line voltage, and performs voltage drop testing at 12A, 15A, and 20A load levels. A large color LCD presents plain-language results for each test mode. The detachable cord enables compact storage. Rated CAT III 135V with auto-shutoff after 5 minutes and 6.6-foot drop protection. Includes pouch. Backed by Klein Tools' 1-year limited warranty.
What is load testing and why would I need it?
The RT390 draws 12A, 15A, or 20A from the circuit while monitoring voltage and checking for tripping. This catches problems — undersized wiring, loose connections, failing breakers — that pass idle testing but show up under actual load conditions.
How does the color LCD improve on LED indicators?
The RT390 displays fault names and test results as readable text on a color screen, eliminating the need to cross-reference LED patterns against a legend — particularly useful in poor lighting or when learning what each result means.
Does the RT390 test AFCI protection?
Yes — same AFCI test function as the RT310. It also tests GFCI protection and detects dual-open faults (simultaneous open neutral and open ground), all displayed on the color LCD.
How long before it auto-shuts off?
5 minutes — compared to 2 minutes on the RT310. This is long enough for most panel-to-outlet test cycles without the tester powering off mid-sequence.
What outlets does the RT390 work with?
Standard 120V AC 3-wire grounded, AFCI-protected, and GFCI-protected North American receptacles.
What separates the RT390 from the RT310?
RT390 adds load testing (12/15/20A), a color LCD display, and a 5-minute auto-shutoff. RT310 covers the same AFCI/GFCI/dual-open tests at a lower price point with LED indicators.
# Klein Tools® RT390 Circuit Analyzer **Model:** `RT390` **Brand:** Klein Tools **Category:** Voltage Tester > The Klein Tools RT390 is a professional-grade circuit analyzer for North American 120V AC three-wire outlets. It identifies wiring faults, inspects both AFCI and GFCI devices with trip time and trip current measurements, displays live line voltage, and performs voltage drop testing at 12A, 15A, and 20A load levels. A large color LCD presents plain-language results for each test mode. The detachable cord enables compact storage. Rated CAT III 135V with auto-shutoff after 5 minutes and 6.6-foot drop protection. Includes pouch. Backed by Klein Tools' 1-year limited warranty. ## Specifications | Attribute | Value | |---|---| | Product Type | Circuit Analyzer | | Voltage Range Ac | 135V AC | | Cat Rating | CAT III 135V | | Tests Gfci | Yes | | Tests Afci | Yes | | Detects Dual Open Fault | Yes | | Load Testing Amps | 12A, 15A, 20A | | Outlet Types Tested | 3-wire 120V AC standard, AFCI, GFCI | | Display Type | Color LCD | | Battery Type | 3 × AAA | | Battery Required | Yes | | Auto Shutoff Min | 5 | | Drop Protection Ft | 6.6 | | Overall Height In | 7.1 | | Overall Width In | 2.7 | | Overall Length In | 1.5 | | Assembled Weight Oz | 10.9 | | Barcode (UPC) | 092644693632 | | Warranty | 1-year limited | ## What's Included - Circuit analyzer - 3 × AAA batteries - Instructions - Pouch Source: https://www.jaspecs.com/klein-tools/voltage-tester/rt390-klein-tools-circuit-analyzer/