Description
The PAI MSW-1238 is a 12V, 4-terminal intermittent-duty relay switch (starter / heavy-load relay) that replaces Mack 2MR358A / 85129178 and Navistar 1825898C94 across Mack heavy trucks and International medium- and heavy-duty trucks. Rated 100 A continuous / 750 A surge, SPST, external ground; mounting and terminal hardware included for direct fit at the OE relay-bracket location on the firewall or starter-circuit junction.
Signs You Need a New Relay Switch
- Single click when turning the key but the engine doesn’t crank
- Intermittent starting — sometimes engages, sometimes nothing
- Rapid clicking when attempting to start (relay chattering)
- Complete electrical silence at the start position despite a charged battery
- Burnt or melted terminals on the existing relay
Specifications
| Manufacturer | PAI Industries |
|---|---|
| Part Number | MSW-1238 |
| Part Type | Relay Switch / Starter Solenoid |
| Voltage | 12V DC |
| Continuous Rating | 100 A |
| Surge Rating | 750 A |
| Terminals | 4 |
| Circuitry | SPST |
| Duty Cycle | Intermittent |
| Ground Type | External Ground |
| Hardware Included | Yes (terminal hardware) |
| Weight | 0.64 lb |
| Warranty | 2-Year Unlimited Mileage |
Cross References
This relay switch replaces or is equivalent to the following part numbers:
- Mack / Volvo: 85129178, 2MR358A, 2MR358, 20563872
- Navistar / International: 1825898C94, 1825898C91, 1826634C94, 1826634C91, 1807230C1, 1807230C2, 1653460C1, 1693494C91, 2587934C91, 1825931C1, 1831646C1, 1825908C1
- Caterpillar: 5L5886
- Delco: 1114537
- Ford: F7TZ-12B533-CA
- Cole Hersee: 24023, 24047
- Prestolite: 15-150
- Fortpro: F23542
Applications
This 4-terminal relay switch fits a wide range of heavy-truck electrical systems wired for the 2MR358A / 1825898C94 relay, including:
- Mack CH, CL, CX, Vision, Granite (GU), Pinnacle (CHU/CXU)
- Mack R, RD, DM, MR vocational
- International 9200i, 9400i, 9900i
- International ProStar, LoneStar, LT
- International 4000, 7000, 8000-series medium/heavy
- Various Sterling, Ford, and Caterpillar 12V applications using the same 2MR358A pattern
Verify the existing relay is the 12V intermittent-duty 4-terminal pattern (not the continuous-duty MSW-1242 / 2MR350 variant) before ordering. Disconnect the batteries before replacement.
