Imperial High And Low Side Couplers Automotive - 21-h & 21-l

Built for Australian refrigeration pros who work with CO₂ systems, the Mastercool 55102-1400 is a tough, oil-filled 70 mm low-side replacement gauge with a dual PSI/MPa scale. It gives you steady, accurate readings on R744—less wobble, fewer do-overs. It’s a bloody good upgrade when a gauge cops a knock.

Key Features & Trade Benefits

• R744-specific low-side gauge — Purpose-built for CO₂ service. Read what you need, fast, without second-guessing.
• 70 mm dial — Clear, high-contrast face. Easier to see on rooftops or in dim plant rooms.
• Dual scale (PSI / MPa) — Flexible units. Swap between standards on mixed-kit jobs with no mental gymnastics.
• Oil-filled movement — Damps vibration. Stable numbers mean quicker charging and fewer call-backs.
• Direct replacement fit — Designed for Mastercool manifolds. Five-minute swap and you’re back on the gauges—no worries.
• Robust build — Field-ready for daily commercial work. She’ll be right on supermarket racks and heat pump callouts.

Why This Product Matters

Real-world scenario: you’re on a supermarket CO₂ rack hunting a nuisance trip. The old low-side gauge flutters like mad and won’t settle. Pop in this oil-filled unit, and your suction pressure stabilises straight away—bang, dial-in is smooth, charge adjustments land first go. That’s time back, fewer comebacks, and a happier client.

Need more gauge options? See our full range here: Refrigerant Gauges Collection.

Pro Tip

Oil-filled gauges read best upright. On high-vibration plant decks, let the needle settle for a second before logging suction. If you’re swapping both sides, replace the high-side at the same time for consistent response—future you will say “fair dinkum, that saved me.”

Compatibility & System Info

• Refrigerant: R744 (CO₂)
• Application: Low-side monitoring on CO₂ refrigeration and CO₂ heat-pump systems
• Manifolds: Direct replacement for compatible Mastercool sets (check your model before ordering)

Local note: Whether you’re on a hot Sydney roof or a chilly Melbourne plant room, the oil fill keeps readings steady when the unit or deck shakes—too easy.

What’s Included

• 1 × Mastercool 55102-1400 low-side oil-filled gauge for R744 (CO₂)

Specifications

Brand / Model	Mastercool 55102-1400
Refrigerant	R744 (CO₂), low-side
Dial Size	70 mm
Fill Type	Oil-filled (anti-flutter)
Scale	Dual scale: PSI / MPa
Use Case	Commercial refrigeration & CO₂ heat-pump service

Warranty & Returns

Covered by store policy and manufacturer warranty. See Shipping & Returns for details.

FAQs

Will it fit my manifold?
It’s a direct replacement for compatible Mastercool manifolds. Match your existing gauge model and connection before purchase.

Can I use it on non-CO₂ refrigerants?
This model is optimised for R744 low-side readings. For other gases, choose the gauge specified for that refrigerant in our Refrigerant Gauges range.

Best partner tools?
If you need a full CO₂ setup, consider a manifold set that’s CO₂-ready and high-pressure hoses (see Related Products below).

Related Products

• Want a full CO₂ rig? This manifold set is a helpful match for commissioning and service: Mastercool CO₂ Manifold 55661G.
• Protect your dials on rough jobs—these covers are a ripper: 80 mm Gauge Protector Set (91553-EE).
• Need hoses for high-pressure work? Check the selection here: Hoses & Couplings.

For Australian guidance on refrigerants (including CO₂/R744) and compliance, see the Australian Government resources here: Australian Government – Refrigerants.