A time relay with a control button is a universal device that allows you to automate the switching on/off of electrical appliances in a car with a time delay. Such relays are actively used to organize delayed start of cooling fans, interior lighting, seat heating, or even to create “comfortable” engine starting systems in the cold season. Unlike standard relays, models with a button allow manual adjustment of timers without the need to reprogram the device or tamper with the wiring.

The main advantage of such relays is the ease of integration into the existing on-board network. For example, you can program the heater to turn on 10 minutes after the ignition is turned off so that the battery does not drain in vain, or configure the additional headlights so that they automatically turn off 30 seconds after the doors are closed. However, when selecting and installing, it is important to consider current characteristics, control type (analog/digital) and compatibility with your vehicle's on-board voltage (usually 12V or 24V).

How a time relay with a button works: principle of operation and types

A time relay with a button is built on the basis of an electromechanical or electronic timer, which controls the closing/opening of contacts after a specified period of time. The key difference from conventional relays is the presence setting buttons, which allows you to set the delay interval manually. Based on the principle of operation, there are two main types:

  • 🔄 Switch-on delay relay — contacts close after a specified time after the control signal is supplied (for example, for a smooth start of powerful consumers).
  • ⏱️ Delayed relay — the contacts open at intervals after the control signal is removed (used for fans, lighting).
  • ⚡ Cyclic relays — alternate on/off with a fixed interval (used in preheating systems).

Most often used in automotive electrical electronic relays (for example, series Omron H3Y or Finder 55.32), since they are compact, not subject to wear and allow you to adjust delays from 0.1 seconds up to 10 o'clock. Mechanical analogues (for example, PFL 102) are cheaper, but have a limited range of time intervals and are sensitive to vibrations.

It is important to understand that the button on the relay body can perform different functions depending on the model: single press — start the timer, retention - reset settings, multiple presses — selecting an interval from pre-programmed values.

📊 What are you planning to use a time relay with a button for?
Cooling Fan Automation
Interior lighting control
Delayed start of heaters
Other uses

Top 5 time relays with a button for a car: comparison of models

The choice of time relay depends on the required delay range, maximum load current and control type. Below are popular models tested in practice by auto electricians. They all keep the tension 12V and have a manual adjustment button.

Model Type Delay range Max. current (A) Features
Omron H3Y-2 Electronic 0.1s – 10h 10 High precision, overvoltage protection
Finder 55.32 Electronic 0.5s – 30min 16 Compact case, LED indication
PFL 102 Mechanical 1s – 10min 8 Low price, simple design
ABB E230 Electronic 0.1s – 2h 12 Waterproof housing (IP65)
Schneider Electric RZ4 Electronic 0.3s – 60min 10 Support 24V, wide temperature range

For most automotive tasks, the optimal choice will be Omron H3Y-2 or Finder 55.32 — they combine accuracy, reliability and ease of setup. Mechanical relays (PFL 102) are suitable for simple fixed-latency systems where high accuracy is not required. When choosing, pay attention to maximum switching current — it must exceed the consumption of the connected load by at least 20%.

⚠️ Attention: Relay with markings AC (alternating current) are not suitable for vehicle networks! Look for models marked DC 12V/24V.

Connection diagrams for a time relay with a button in a car

Connecting a time relay depends on its type and task. Below are two basic diagrams for the most common scenarios: shutdown delay (for example, for a fan) and switch-on delay (for example, for a heater). In all cases, use a fuse on the relay supply line!

Diagram 1. Shutdown delay (cooling fan):



+12V (from ignition) → Relay contact 85


Contact 86 → Ground


Pin 87 → Load (fan)


Contact 30 → +12V (constant)

When the ignition is turned off, the relay continues to supply power to the fan for a set time (set by button).

Diagram 2. Switch-on delay (seat heating):



+12V (from the button in the cabin) → Contact 85 of the relay


Contact 86 → Ground


Pin 87 → Load (heating)


Contact 30 → +12V (constant)

After pressing the button in the cabin, the heating turns on after a specified delay (for example, 5 minutes).

For a cyclic relay (for example, for a flashing strobe), an additional contact is used 87a, which switches between 30 and 87 with a given frequency. When connecting powerful consumers (more than 10A), use an additional power relay so as not to overload the timer contacts.

Check the on-board voltage with a multimeter

Make sure the maximum relay current is greater than the load current

Use heat shrink tubing to insulate connections

Connect a fuse to the relay power line -->

Common installation mistakes and how to avoid them

Even experienced auto electricians sometimes make mistakes when working with time relays, which leads to incorrect operation of the system or failure of the device. Here are the most common problems and how to prevent them:

  • ⚡ Wrong polarity - many electronic relays are sensitive to connection polarity. If the device does not work after installation, check the connection +12V and masses multimeter.
  • 🔥 Contact overload — connecting a load with a current higher than permissible leads to burning of the contacts. Always use a buffer relay for powerful consumers (eg heater starter).
  • ⏳ Unaccounted for power surges — voltage surges of up to 14.8V (when the generator is running). Choose a relay with a voltage reserve (for example, DC 12–24V).
  • 📡 Interference from other devices - if the relay operates randomly, check the shielding of the wires and add a capacitor 0.1 µF parallel to the relay coil.

One of the most insidious mistakes is ignoring leakage current. Electronic relays in standby mode can consume up to 10–20 mA, which will drain the battery in a few days. To avoid this, connect the relay power through an additional switch or use models with a complete shutdown function (for example, Omron H3Y-N).

⚠️ Attention: If the time relay is installed in the engine compartment, place it in a sealed housing or use models with protection IP65 and above. Condensation and oil splashes quickly damage exposed electronics.
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Before final assembly, check the operation of the relay on the table by connecting it to the power supply 12V with a load (for example, a light bulb). This will help avoid installation errors in the car.

Setting up a time relay: step-by-step instructions

The setup process depends on the relay model, but the general algorithm is the same for most devices. Let's look at an example based on the popular Finder 55.32:

  1. Connect the relay to the power source 12V (observe polarity!). Make sure the load is off.

  2. Press and hold the setup button (usually labeled SET or TIME) during 3–5 secondsuntil the indicator lights up.

  3. By briefly pressing the same button, select the desired delay interval. B Finder 55.32 setup step - 1 second (up to 30 seconds) or 1 minute (over 30 seconds).

  4. To save the settings, release the button and wait until the indicator blinks (usually 2–3 times).

  5. Apply a control signal (for example, turn on the ignition) and check the relay operation at a specified interval.

In relay Omron H3Y-2 setting is carried out by a combination of long and short presses: 1 short — mode selection (on/off delay), 1 long — transition to setting the time, short presses — change of value.

For cyclic relays (eg ABB CT-MFS) the duration of the pulse and pause is additionally adjusted. It is important to consider here that total cycle (on + off) should not exceed the maximum permissible interval for a particular model.

How to reset relay settings to factory settings?

For most relays, reset is accomplished by holding the setting button for 10–15 seconds until the indicator (usually red) blinks. In models Omron This may require turning off the power, pressing the button, and then applying power again while holding it down. Look for details in the datasheet of the specific model.

Practical application: 3 ready-made solutions for the car

A time relay with a button allows you to implement many useful functions in your car without complex programming. Here are three proven solutions that you can put together yourself:

1. Automatic cooling fan shutdown

Problem: After stopping the engine, the fan continues to run, draining the battery.

Solution: Connect a relay Finder 55.32 according to the shutdown delay scheme with interval 2–3 minutes. Take the relay power from the ignition line, and the load will be the fan. Now, after turning off the ignition, the fan will run for the specified time and turn off.

2. Delayed start of the interior heater

Problem: The heater turns on immediately when the engine starts, putting a strain on the battery.

Solution: use a relay Omron H3Y-2 with delay 30–60 seconds. Take the control signal from the line +12V after turning on the ignition. The heating will start working only after the engine has warmed up.

3. Interior lighting with delay

Problem: the interior light goes out immediately after closing the door, which is inconvenient in the dark.

Solution: Connect a relay PFL 102 parallel to the standard backlight switch. Set the shutdown delay to 15–20 seconds. The light will now stay on longer after the door is closed.

To implement these schemes you will need: time relay (select by load current), fuse (at 5–10A), heat shrink tube or electrical tape multimeter to check connections.

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When connecting the time relay to the car's standard circuits (for example, to the ignition), use diode decoupling module (for example, 1N4007), to avoid parasitic currents in the on-board network.

Maintenance and troubleshooting

A time relay is a reliable device, but in automotive conditions it is susceptible to vibration, moisture and temperature changes. To extend service life, follow simple rules:

  • 🔧 Periodic check — once every six months, test the operation of the relay by applying a control signal and measuring the response time with a stopwatch.
  • 🌡️ Temperature control - if the relay is installed on the engine, make sure that its housing does not heat up above 70°C (for most models).
  • 🔌 Cleaning contacts — if there are signs of oxidation (load flickering), clean the relay contacts with alcohol or a special liquid Contact Cleaner.

If the relay stops operating, check the following:

  1. Availability of power on contacts 85 and 86 (must be 12V and mass, respectively).

  2. Continuity of the fuse on the power line.

  3. Load condition - perhaps the problem is not in the relay, but in the connected device (for example, the heater coil has burnt out).

  4. Correct settings - reset the relay to factory settings and configure again.

If the relay operates randomly, the reason may lie in dietary interference. In this case add LC filter (choke + capacitor) to the relay power line or use shielded wires. For diagnostics, connect the oscilloscope to the pin 85 — if high-frequency bursts are visible on the screen, the problem is confirmed.

FAQ: Frequently asked questions about time relays with a button

Is it possible to use a 220V relay in a car?

No, relays are designed for 220V AC not suitable for vehicular networks 12V/24V DC. Look for models marked DC 12V or DC 24V. Connecting a 220V relay to the on-board network will lead to its instant failure.

How to connect a time relay to an alarm system?

For integration with alarm systems, use the output +12V from the alarm unit, which is activated when arming. Connect it to the contact 85 relay, and the load (contact 87) make, for example, an additional strobe. Set the relay to switch on delay 10–15 secondsso that the light signals are activated after the security is activated.

Why does the time relay operate with a delay different from the configured one?

This can be caused by several reasons: 1) Unstable power supply - check the voltage at the contacts 85 and 86 multimeter (should be 12V±10%). 2) Temperature drift - electronic relays at low temperatures (below 0°C) may slow down the response. Use temperature compensated models. 3) Mechanical wear - In pneumatic or motor relays, the operating speed changes over time. The solution is to replace it with an electronic analogue.

Is it possible to connect a time relay to a car's CAN bus?

Direct connection to the CAN bus is not recommended, since the time relay is not designed to work with digital protocols. However you can use CAN module (for example, ELM327) to read signals (such as engine speed or rpm) and apply control voltage to the relay through a transistor circuit or an additional relay.

Which time relay to choose to control the heater starter Webasto?

For Webasto or Eberspächer A relay with a switch-on delay and a current of at least 20A (for example, Schneider Electric RZ4-DC24). Important: 1) Use buffer relay to relieve timer contacts. 2) Set the delay to 5–10 minutes after starting the engine, so that the heater turns on only after warming up. 3) Connect relay power via fuse 15A.