Genuine Mack 2MR2149 Relay Switch | 12V 35/20 AMP 5-Pin | Fits Horn & Engine Brake

Restore electrical reliability with this Genuine OEM Mack Relay Switch.

The Mack 2MR2149 (often referenced as 2MR2149M) is a versatile 12V multi-purpose relay used across various Mack truck platforms. Featuring a standard 5-pin configuration and rated for 35/20 Amps, this relay is a critical component for high-draw systems such as horns, ignition feeds, and engine brake disable circuits.

Using a genuine Mack Bulldog part ensures proper resistance and switching speeds that aftermarket "universal" relays often fail to match, preventing electrical gremlins and protecting your truck's wiring harness.

Key Features:

• Genuine Mack OEM: Direct replacement for part number 2MR2149 and 2MR2149M.

• High-Performance Specs: 12 Volt, 5-Terminal, 35/20 Amp rating.

• Versatile Application: Commonly used for Horns, Engine Brakes, Ignition Feed, and accessory circuits.

• Condition: New Old Stock (NOS) — Unused, original OEM quality.

Interchange & Cross-Reference:

• Mack / Volvo: 2MR2149M, 2MR2154M, 3968336, 25195197, 25082390.

• Freightliner: 23-13265-001.

• Navistar / International: 3516015, 3516015C1, 2602142, 2602142C1.

Other: Song Chuan 301-1C-D-R1, PAI MSW-1237, TruckAC T5299

Common Slot Locations:

• Mack Granite (GU): Typically found in slots R1 (Horn) and R4 (Engine Brake).

• Mack Vision (CXU): Frequently used for Marker Lamps and Ignition Switched Power.

• Intermittent Electrical Tip: If your horn or engine brake works only "sometimes," the internal contacts of this relay are likely pitted or burnt. Replacing with a Genuine Mack 2MR2149 ensures proper amperage draw and protects your ECM from voltage spikes.