Mastercool 55800 electronic leak detector – ultra-sensitive with LCD display

Looking for precision leak detection on refrigerant lines? The Mastercool 55800 is built to detect even the tiniest leaks in HVAC and refrigeration systems—keeping your installs tight and your systems efficient.

What you'll find on this page

• ✅ Key detection capabilities
• ✅ LCD display and smart sensor features
• ✅ Sensitivity modes and operation
• ✅ What’s in the box + replacement parts
• ✅ Download user manual

Detects a wide range of gases

This unit is compatible with virtually all refrigerants, including newer blends. It uses a high-performance metal oxide sensor to pinpoint leaks with precision.

• ✅ Detects all CFCs, HCFCs, and HFCs
• ✅ Compatible with R134a, R1234yf, R410A, R407C, and R32
• ✅ Also detects hydrogen and combustible gases
• ✅ Exceeds SAE J2791 (R134a), J2913 (R1234yf), and EN 14624 standards

LCD display and smart sensor feedback

The clear LCD screen shows signal levels, sensitivity mode, and diagnostic indicators. It’s backed by a smart microprocessor that automatically adjusts for optimum sensor performance.

• ✅ Vertical signal bars show leak strength
• ✅ H–M–L sensitivity range indicators
• ✅ WAIT and READY status for accurate readings
• ✅ INT alert for environmental interference or sensor issue
• ✅ Low battery and error (E1–E9) codes displayed

Custom sensitivity modes for leak size

Three sensitivity settings let you adjust based on leak size or refrigerant type. A “Super Sensitive” mode is ideal for detecting low-volume leaks in R1234yf and other modern blends.

• ✅ High: ≥ 0.05 oz/yr (1.5 g/yr)
• ✅ Medium: ≥ 0.25 oz/yr (7 g/yr)
• ✅ Low: ≥ 0.5 oz/yr (14 g/yr)
• ✅ HOLD and PEAK buttons help isolate hard-to-find leaks
• ✅ Volume/Mute function for audio control

What’s in the box + replacement parts

Everything you need comes packed in a durable case—ready for field work. Easy-to-replace consumables mean your tool stays reliable long term.

• ✅ 55800 unit with 16” flexible probe
• ✅ 2 x “D” batteries
• ✅ Leak test vial (Part #55800-VL)
• ✅ 3 replacement filters (Part #55800-FILTER)
• ✅ Blow-moulded storage case
• ✅ Sensor life: 2000 hours
• ✅ Battery life: 60 hours continuous use
• ✅ Operating temperature: 0 to 140˚F

Download the user manual

Need the full specs, operation guide, or replacement procedures? Get the complete instruction manual below.

• ✅ Click here to download the 55800 leak detector manual

From automotive AC to commercial HVAC, the Mastercool 55800 is the tool that pros trust for leak detection done right.