Standard Ignition RY-1666 Diesel Glow Plug Relay
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Standard Ignition

Standard Ignition RY-1666 Diesel Glow Plug Relay

Brand Standard Ignition RY-1666
Connector Gender Male
Connector Quantity 4
Connector Shape Square
Functions Relay
Mounting Bracket(s) Included No
Terminal Gender Male
Terminal Quantity 4
Terminal Type Blade terminals
Voltage 12
Fits GMC · 4 vehicles

Durable composite housing. Helps protect against harsh heat and severe under-hood conditions.

Aluminum contacts. Built for durability and long service life.

Epoxy-sealed relay. Helps keep out dust, heat, and moisture.

Cross-references Dorman - OE Solutions 904-100, Four Seasons 20735 and 1R2078 for the same application. See all 9.

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Diesel Glow Plug Relay for GMC Sierra 2500 HD

Standard Ignition RY-1666 is a 12-volt diesel glow plug relay built for emission control systems that need reliable cold-start operation. It is a direct-fit relay for 2001-2004 GMC Sierra 2500 HD applications listed below, including relay-only service.

  • 12-volt relay for diesel glow plug control
  • 4-pin male connector with square connector shape
  • 4 male blade terminals for OE-style electrical connection
  • Composite housing helps protect against heat and severe under-hood conditions
  • Aluminum contacts support durability and long service life
  • Epoxy-sealed construction helps resist dust, heat, and moisture
  • Manufactured in TS16949 and ISO9001 certified facilities

Application Details

Compatible With 2001-2004 GMC Sierra 2500 HD, relay only. This Standard Ignition RY-1666 relay cross-references Dorman OE Solutions 904-100 for the same application. It also aligns with related aftermarket references including Four Seasons 20735.

In diesel starting systems, the glow plug relay controls power delivery to the glow plugs so the engine can reach the temperature needed for startup. On a GMC Sierra 2500 HD, a worn relay can interrupt that circuit and affect cold-start performance, especially in lower temperatures.

Common Issues This Part Can Address

  • Hard starting during cold weather
  • Glow plugs not receiving power
  • Intermittent relay operation
  • Extended cranking before engine start
  • Electrical faults in the glow plug control circuit

Installation Notes

Verify the connector style, terminal layout, and 12-volt specification before installation. This relay uses a square 4-pin male connector with blade terminals and does not include a mounting bracket. Confirm the vehicle is a 2001-2004 GMC Sierra 2500 HD and that the repair callout is relay-only before replacing the part.

Quality Assurance

Standard Ignition manufactures this relay in certified TS16949 and ISO9001 facilities, with composite housing, aluminum contacts, and epoxy protection selected to support consistent electrical performance in demanding under-hood environments.

This part fits 4 vehicles
Always verify fitment with your vehicle's VIN if unsure. Submodel & trim restrictions may apply.
YearMakeModelFuel TypeNotes
2004GMCSierra 2500 HDDIESELRelay Only
2003GMCSierra 2500 HDDIESELRelay Only
2002GMCSierra 2500 HDDIESELRelay Only
2001GMCSierra 2500 HD—Relay Only
Directly replaces or cross-references 9 part numbers
Cross-reference numbers are provided for identification purposes only. Always confirm fitment before ordering.
Dorman - OE Solutions — 904-100Four Seasons — 207351R207856-24276011007197371492AR7170R7169RAA2671