6 Electrical switch & relay parts are listed for the 1978 Checker Marathon, in 3 part types, covering all 3 engine options (4.1L 250cid L6, 5.0L 305cid V8 and 5.7L 350cid V8). Each one has a brand, a manufacturer part number and notes that say where it fits.
The switch and relay system on the 1978 Checker Marathon covers the switches, relays and flashers that route power to everything the driver touches. All 6 listed parts are Horn Relay (3 parts), Fuel Pump Cutoff Switch (2 parts) and Accessory Power Relay (1 part).
The 1978 Checker Marathon was sold with 3 engines. Every part on this page is engine-specific. Each part shows which engine(s) it fits.
The most listed brands for 1978 Checker Marathon electrical switch & relay parts are ROSTRA (2 parts), STANDARD MOTOR PRODUCTS (2 parts) and ACDELCO (1 part), plus 1 more brand.
Each part number listed for the 1978 Checker Marathon opens a page with every vehicle that part fits.
Accessory Power Relay
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| ROSTRA Fits: 5.0L 305cid V8 | 600426 | 🇺🇸 US 🇨🇦 CA | View on Amazon |
This table covers the relays that control the Accessory Power circuit. Typical signs include a click with no action, or a circuit that works only when you swap in a known-good relay. Swap with an identical relay in the fuse box before buying — it is the fastest test there is.
One part is listed for the 1978 Checker Marathon — ROSTRA 600426.
Fuel Pump Cutoff Switch
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| ACDELCO Fits: 5.0L 305cid V8 | D1876D | 🇺🇸 US 🇨🇦 CA | Gold | View on Amazon |
| STANDARD MOTOR PRODUCTS Fits: 5.0L 305cid V8 | FV7 | 🇺🇸 US 🇨🇦 CA | View on Amazon |
This table covers the Fuel Pump Cutoff switches. Typical signs include a function that works intermittently, or a click without the accessory coming on. Inspect the connector behind the switch; heat-damaged terminals will kill the new part too.
2 Fuel Pump Cutoff Switch parts for the 1978 Checker Marathon come from 2 brands — ACDELCO and STANDARD MOTOR PRODUCTS.
This group includes ACDELCO D1876D and STANDARD MOTOR PRODUCTS FV7.
Horn Relay
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| ROSTRA Fits: 5.0L 305cid V8 | 600426 | 🇺🇸 US 🇨🇦 CA | View on Amazon | |
| STANDARD MOTOR PRODUCTS Fits: 5.0L 305cid V8 | HR138 | 🇺🇸 US 🇨🇦 CA | View on Amazon | |
| WELLS Fits: 5.0L 305cid V8 | 1R2217 | 🇺🇸 US 🇨🇦 CA | Mounting Bracket Included: YES | View on Amazon |
This table covers the relays that control the Horn circuit. Typical signs include a click with no action, or a circuit that works only when you swap in a known-good relay. Swap with an identical relay in the fuse box before buying — it is the fastest test there is.
3 Horn Relay parts are listed for the 1978 Checker Marathon, from ROSTRA, STANDARD MOTOR PRODUCTS and WELLS.
This group includes ROSTRA 600426, STANDARD MOTOR PRODUCTS HR138 and WELLS 1R2217.
Buying Electrical Switch & Relay Parts for a 1978 Checker Marathon
On this vehicle, the switch and relay system covers the switches, relays and flashers that route power to everything the driver touches.
- Match the engine first. Every electrical switch & relay part here is engine-specific; each row shows which engine(s) it fits.
- Read the notes on each row for position, trim and spec qualifiers before you order.
- Where labor overlaps, inspect the connector terminals behind any failed switch — heat damage there will kill the new part too.
- Cross-reference the manufacturer part number against your old part or a service-manual listing.
Start with the largest groups on this page: Horn Relay and Fuel Pump Cutoff Switch .
Frequently Asked Questions
How many electrical switch & relay parts fit the 1978 Checker Marathon?
Our catalog currently lists 6 electrical switch & relay parts for the 1978 Checker Marathon across 3 subcategories and 4 brands, covering all 3 engine options (4.1L 250cid L6, 5.0L 305cid V8 and 5.7L 350cid V8). Each part is matched to the engine(s) it fits.
Do electrical switch & relay parts differ between 1978 Checker Marathon engines?
Yes. Every electrical switch & relay part on this page is engine-specific. Each row shows which engine(s) it fits — use the filter at the top to hide the rest. If you're unsure which engine you have, check the emissions label under the hood or the 8th character of your VIN.
What are the signs of electrical switch & relay problems on a 1978 Checker Marathon?
Common symptoms include accessories that work intermittently, a click without action, or one function dead while its fuse tests fine. If you notice any of these, identify the affected subcategory above and cross-reference the part numbers listed.
What should I replace at the same time?
Where labor overlaps, inspect the connector terminals behind any failed switch — heat damage there will kill the new part too.
What do the market flags (US, CA, MX) on each part mean?
They show the market for which the manufacturer published application data for that part — where the vehicle was first sold, not where the part was made. If your 1978 Checker Marathon was originally sold in the US, the safest choice is a part marked for the US market.
How do I make sure a part fits my 1978 Checker Marathon?
First match the engine — each row shows which engine(s) the part fits. Then swap a suspect relay with an identical known-good one from the fuse box before buying — it is the fastest diagnostic there is. The notes column carries position and trim qualifiers where they apply.
Other Parts for the 1978 Checker Marathon
Electrical Switch & Relay Parts for Other Checker Marathon Years
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