Side-by-Side Comparison
Electrical & Ignition Standards
Automotive Relays & ISO Pinouts vs. Spark Plug Threads & Dimensions
Comparing 2 standards across 16 specifications. 16 key differences identified.
Comparing:
Automotive Relays & ISO Pinouts
Spark Plug Threads & Dimensions
Automotive electromechanical relays switch high-current vehicle loads (cooling fans, fuel pumps, headlights, starter solenoids) using low-current control signals, standardized under ISO 7588 into Mini (1-inch cube) and Micro form factors with standard DIN 72552 terminal numbering (30, 85, 86, 87, 87a).
Internal combustion engine spark plugs are standardized under ISO 1919 and SAE J548 into standard metric thread diameters (M10×1.0, M12×1.25, M14×1.25, M18×1.5), thread reaches (9.5mm to 26.5mm), hex wrench drive sizes (14mm, 16mm / 5/8", 21mm / 13/16"), and terminal configurations.
Specification Comparison Table
16 Parameters| Parameter / Spec | ||
|---|---|---|
|
Governing Standards
|
ISO 7588 / DIN 72552 / SAE J2544 | ISO 1919 / ISO 2344 / ISO 28741 / SAE J548 |
|
Form Factor Tiers
|
ISO Mini Relay (~28×28×25 mm) / ISO Micro Relay (~22×15×25 mm) / Maxi Relay | — |
|
Contact Switching Ratings
|
Mini: 30A to 50A at 14V DC | Micro: 20A to 35A at 14V DC | — |
|
Nominal Coil Voltages
|
12V DC (automotive passenger cars) / 24V DC (heavy commercial trucks) | — |
|
Terminal 30 (DIN 72552)
|
Common High-Current Power Input (Fused Battery B+ feed) | — |
|
Terminal 85 (DIN 72552)
|
Relay Coil Ground / Trigger Return (connected to ECU or ground switch) | — |
|
Terminal 86 (DIN 72552)
|
Relay Coil Power (+12V ignition switch or control trigger) | — |
|
Terminal 87 (DIN 72552)
|
Normally Open (NO) Output — Energized when coil is activated | — |
|
Terminal 87a (DIN 72552)
|
Normally Closed (NC) Output — Energized when coil is unpowered (5-pin SPDT only) | — |
|
Standard Automotive Thread
|
— | M14 × 1.25 mm (dominates ~80% of passenger vehicle engines) |
|
Downsized Modern Engine Thread
|
— | M12 × 1.25 mm (modern turbocharged direct-injection engines) |
|
Small Engine / Powersports Thread
|
— | M10 × 1.0 mm (powersports, motorcycles, chainsaws) |
|
Heavy-Duty / Industrial Thread
|
— | M18 × 1.5 mm (vintage tractors, industrial stationary gas engines) |
|
Common Hex Drive Sizes
|
— | 14.0 mm (Bi-hex / 12-point), 16.0 mm (5/8" hex), 20.6 mm (13/16" hex) |
|
Standard Reach Depths
|
— | Short (9.5 mm / 3/8"), Standard (19.0 mm / 3/4"), Long Reach (26.5 mm / 1.04") |
|
Standard Spark Gap
|
— | 0.028"-0.032" (0.7-0.8 mm turbo) / 0.040"-0.044" (1.0-1.1 mm NA) |