EA101 – 3 Gauge Adjustable Alarm Module (12 / 24 VDC)
Early-warning protection for oil pressure, temperature and gearbox systems
Overview
The Bolec EA101 Three Gauge Adjustable Alarm is a compact monitoring module designed to trigger an alarm output whenever the reading from any one of three gauges crosses a pre-set fault threshold.
Ideal for diesel engines and industrial equipment, the EA101 provides early warning for
low engine oil pressure, high engine temperature, and low gearbox oil pressure.
Compatible with standard resistance gauges such as VDO-type senders, the EA101 works with any variable-resistance-to-ground sensor and variable DC signal.
It can also be used without gauges—by wiring directly to the sender.
Key Features
- ✅ Works with 12 V or 24 V DC negative-ground systems
- ✅ Three independent alarm channels (LOP, HET, LGBP)
- ✅ 25-turn precision potentiometers for fine adjustment
- ✅ Transistorized output switching to ground (up to 0.25 A per channel)
- ✅ LED indicators for visual setup and testing
- ✅ Compact, universal mounting – approx 58 × 42 × 29 mm
Typical Applications
The EA101 is frequently installed in:
- 🛠 Diesel and petrol engines – to safeguard against low oil pressure or overheating
- 🚜 Agricultural and irrigation pumps – for gearbox and bearing protection
- 🚛 Heavy vehicles, marine and generator sets – for early-warning alarms
- ⚙️ Custom dashboards – as a flexible, multi-channel alarm controller
How It Works
Each input channel monitors the voltage from a sender or gauge. When the voltage rises or falls past the
pre-set threshold, the EA101’s internal transistor switches the corresponding output to ground,
activating a connected lamp, buzzer, or relay.
Each channel can be precisely tuned using its 25-turn trimmer pot while observing the LED indicator:
turn anticlockwise until the LED turns off, then slowly clockwise until it just lights.
Fine-tune by varying sender resistance to confirm the alarm point.
Connection Summary
- IGN + → Switched +12 / 24 V supply (via 0.5 A fuse)
- – GND → Good chassis earth
- SNDRS (LOP / HET / LGBP) → Connect to each gauge sender terminal
- ALARMS (LOP / HET / LGBP) → Connect to the negative side of a lamp, buzzer or relay coil
Note: Outputs switch to ground internally. Each alarm output rated 0.25 A (resistive).
Setup Tips
- 💡 Use a test light instead of your final alarm during calibration for easier viewing.
- ⚡ Fit reverse-EMF diodes across relay or solenoid coils to protect electronics.
- 🔋 Remember: the EA101 cannot operate if supply, gauge or sender fails – make all circuits fail-safe where possible.
Technical Specifications
| Supply Voltage | 12–24 V DC (negative ground) |
| Current Draw | ≈ 10 mA quiescent |
| Adjustment Range | 0 – 10 V DC (at sender input) |
| Output Rating | 0.25 A per output (resistive) |
| Dimensions | 58 × 42 × 29 mm |
| Power Dissipation | 1 W @ 25 °C / 0.6 W @ 85 °C |
Installation Diagram
The EA101 includes clear labeling for SNDRS and ALARMS terminals, plus built-in LEDs for each channel.
Typical wiring connects to oil pressure, engine temperature and gearbox pressure senders with the alarm outputs driving lamps or buzzers.
Tip: When using the sender alone (without gauge), insert a 1 kΩ 1 W resistor in series as shown in the manual.
Why Choose the EA101?
Bolec has been designing and manufacturing Australian-made electronic modules for over 40 years.
The EA101 continues this tradition—offering reliability, easy installation and field-proven protection for critical machinery.
Whether you’re maintaining a generator, truck, or irrigation pump, the EA101 helps prevent costly damage by giving you an early warning before failure occurs.
Bolec Electronics Pty Ltd | Australian designed & manufactured modules for engine protection and control systems.