Britax

Micro Relay — RM4-1235R 35A 12V 4-Pin N/O Resistor

Name: Britax Micro Relay — RM4-1235R 35A 12V 4-Pin N/O Resistor
Brand: Britax
SKU: RM4-1235R
Price: 11.00 AUD
Availability: InStock

RM4-1235R

12V 35A single-contact micro-ISO relay with resistor coil protection. Switches lights, horns, compressors and pumps on 4WDs, caravans, boats and motorcycles. Plugs into any micro-ISO 4-pin base.

35A · 12V DC

4-pin micro-ISO

Resistor coil protection

$11.00

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Universal fitment12V DC 35A SPST switching relay for mid-range accessories

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A micro-ISO relay from Britax that switches up to 35A continuous on a single 12V DC circuit. Drives mid-range accessories like driving lights, LED work lights, horns, fuel pumps, radiator fans and compressor triggers off a low-current switch or ignition-sense wire. Fits any standard micro-ISO 4-pin relay base, so it drops straight into existing fuse-and-relay panels in 4WDs, utes, caravans, campers, trailers, boats and motorcycles.

The body is 15 by 15mm and 22mm tall in a sealed Polyamide housing with the standard micro-ISO 4-pin footprint and 2.8mm blade terminals. Pin 85 and 86 take the coil feed, pin 30 is the battery feed, and pin 87 is the switched output. A resistor across the coil terminals absorbs the voltage spike when the relay drops out, so the coil kickback does not get fed back into sensitive dash switches or ignition-sense modules. Weighs 20g.

Rated for 35A on the normally-open contact. For loads above 35A, step up to the Britax R4-1280R 80A heavy-duty mini relay; for winches and large inverters use a solenoid or motor contactor sized to the actual current. Fuse the main feed at the battery with a 30A blade matched to the downstream circuit, not above the 35A relay rating.

Pairs with

Mini Relay Base — 4 & 5 Pin ISO Stackable

$6.00

35A Continuous — switches mid-range accessories up to 35A
Micro-ISO Footprint — plugs into any 2.8mm 4-pin micro relay base
Resistor Coil Protection — absorbs the kickback when the relay drops out
Normally Open — load off until the trigger closes the coil
12V Coil — matches standard automotive battery feeds
Compact Body — 15 by 15mm and 22mm tall, fits where mini relays won’t
Low Coil Draw — 0.15A triggerable from any ignition-sense or dash switch
Trade-Brand Catalogue — Britax mainstream AU auto-electrical supplier

Electrical

Voltage | 12V DC

Switched current | 35A continuous

Contact | SPST N/O

Pin count | 4

Pin pattern | Micro-ISO 280 Series

Coil draw | 0.15A at 12V

Protection | Resistor across coil

Operating temp | -40°C to +85°C

Physical

Dimensions | 15 × 15 × 22 mm

Weight | 20g

Terminals | 2.8mm blade

Housing | Polyamide (PA66)

Country of origin | China

Length: 15mm

Width: 15mm

Height: 22mm

Weight: 0.02kg

12V DC 35A SPST switching relay for mid-range accessories

12V DC vehicles including 4WDs, caravans, campers, trailers, boats and motorcycles

Driving lights, LED work lights, horns, fuel pumps, radiator fans and compressor triggers (loads up to 35A continuous)

Micro-ISO 4-pin pattern, drops into any standard micro relay base or socket

Not for loads above 35A continuous. Step up to a Britax R4-1280R 80A heavy-duty mini relay for larger loads

Not for 24V systems. This is 12V coil only. Use the Britax RM4-2435R 24V micro relay for 24V vehicles

Not for mains voltage. DC only, maximum 32V DC

Q: What does ‘micro-ISO’ actually mean?
Micro-ISO is the smaller of the two standard automotive relay base patterns. The relay body is roughly 15 by 15mm and sits on a 4-pin or 5-pin base with 2.8mm blade terminals in a fixed layout. Any 4-pin micro-ISO relay drops into any 4-pin micro-ISO base, regardless of brand.

Q: What does ‘35A N/O’ mean?
35A is the continuous current the switched contact can carry. N/O stands for normally open — the contact sits open with no coil power, and closes when the coil energises. One contact pair, one circuit on or off. No changeover second contact like a 5-pin relay has.

Q: Why does it need resistor protection?
When the coil powers off, the collapsing magnetic field dumps a reverse-polarity voltage spike (coil kickback) back into the trigger wire. A resistor across the coil terminals absorbs that spike before it reaches the switch or module that drove the coil, protecting ignition-sense modules, ECUs and dash switches from damage.

Q: Will this work with 24V trigger systems?
No. The coil is wound for 12V. A 24V trigger will overload the coil, overheat the resistor and burn out the relay quickly. For 24V vehicles use the Britax RM4-2435R 24V micro relay instead.

Q: What size cable and fuse should I run on the switched side?
Run 4mm² (12 AWG) automotive cable from the battery to the relay 30 pin and from the relay 87 pin to the load. Fuse at the battery source with a 30A blade fuse (sized to the cable and the downstream load, below the 35A contact rating). The trigger side (85/86) only needs light wire — 1mm² or 18 AWG is plenty for the 0.15A coil draw.

Q: Can I run a winch through this?
No. Winches draw 200 to 500A under load, which is more than ten times what this relay carries. A winch needs a dedicated solenoid or motor contactor rated for continuous winch current. For loads 80A or below step up to the Britax R4-1280R heavy-duty mini relay; for winches use an Albright-style contactor.

Q: Where does the resistor sit?
Inside the housing, wired across the two coil terminals (pins 85 and 86). You never see it or wire it externally. It just sits there and absorbs the voltage spike each time the coil drops out.

Q: Does the base matter?
Any 4-pin micro-ISO base with 2.8mm blade terminal receptacles accepts this relay, regardless of brand. Narva, Hella, Durite, MTA, Britax and Elevate micro-ISO bases are cross-compatible because the pin pattern is a published standard. For a loose relay with pigtail flying leads, use the Elevate mini relay base with terminals shown below.

Q: Can it mount upside-down or sideways?
Yes. Sealed relay housings can mount at any angle. Water drainage is not a concern on a sealed thermoplastic micro-ISO relay. Mount it however the fuse-and-relay panel geometry works.

Q: What is the coil current draw?
About 0.15A at 12V, which is roughly 1.8 watts. Low enough that any ignition-sense wire, dash switch or module driver stage can trigger it directly without needing an interposing relay.

Q: How does it compare to the 24V version?
Identical housing, identical pin pattern, identical 35A switched rating. The only difference is the coil winding. The 12V RM4-1235R is for 12V vehicles (4WDs, utes, caravans, boats); the 24V RM4-2435R is for 24V vehicles (trucks, buses, agricultural, 24V marine). Pick the one that matches the trigger-side voltage in your vehicle.

Q: What warranty is on this?
12 months against manufacturing defects. Covers coil failure, contact welding, cracked housing and dead-on-arrival parts when wired and fused within the 35A ceiling and installed in a 12V system. Does not cover damage from over-current, reverse polarity, external short-circuit faults, or water ingress.

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