This page lists 26 electrical switch & relay parts for the 2018 Audi A8, across 12 part types, covering all 3 engine options (3.0L V6 Supercharged, 4.0L V8 Turbocharged and 6.3L W12). Every part shows its brand, manufacturer part number and fitment notes.
On the 2018 Audi A8, the switch and relay system covers the switches, relays and flashers that route power to everything the driver touches. 14 parts of the 26 listed are Power Window Switch (7 parts), Brake Light Switch (4 parts) and Accessory Power Relay (3 parts). The other 9 part types cover the remaining 12 parts.
The 2018 Audi A8 was sold with 3 engines. Every part on this page is engine-specific. Each part shows which engine(s) it fits.
9 brands supply electrical switch & relay parts for the 2018 Audi A8, led by WELLS (10 parts), HELLA (5 parts) and STANDARD MOTOR PRODUCTS (5 parts), plus 6 more brands. Quality grades include Standard Replacement and Economy.
A "Popular" badge means the source catalog flagged the part as frequently chosen for the 2018 Audi A8. 2 parts have it, including WELLS 1S13089 (Power Window Switch) and WELLS 1S13092 (Power Window Switch). Each part number opens a page with every vehicle that part fits.
A/C Condenser Fan Motor Relay
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| HELLA Fits: 6.3L W12 | 933332451 | 🇲🇽 MX | 4-pin connector | View on Amazon |
This table covers the relays that control the A/C Condenser Fan Motor 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 2018 Audi A8 — HELLA 933332451.
A/C Refrigerant Pressure Switch
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| FOUR SEASONS Fits: 6.3L W12 | 37427 | 🇲🇽 MX | Pressure Switch | View on Amazon |
This table covers the pressure switches on the A/C circuit. 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.
One part is listed for the 2018 Audi A8 — FOUR SEASONS 37427.
A/C Thermo Switch
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| GPD Fits: 6.3L W12 | 1713414 | 🇲🇽 MX | Thermistor | View on Amazon |
This table covers the A/C Thermo 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.
This group shows a single part: GPD 1713414.
Accessory Power Relay
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| HELLA Fits: 6.3L W12 | 933332451 | 🇲🇽 MX | 4-pin connector | View on Amazon |
| STANDARD MOTOR PRODUCTS Fits: 6.3L W12 | RY577 | 🇲🇽 MX | Functions: Fuel Pump Relay | View on Amazon |
| WELLS Fits: 6.3L W12 | 1R2303 | 🇲🇽 MX | Mounting Hardware Included: No | 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.
3 Accessory Power Relay parts for the 2018 Audi A8 come from 3 brands — HELLA, STANDARD MOTOR PRODUCTS and WELLS.
Part numbers include HELLA 933332451, STANDARD MOTOR PRODUCTS RY577 and WELLS 1R2303.
Brake Light Switch
Economy
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| DORMAN Fits: 6.3L W12 | 920497 | 🇲🇽 MX | View on Amazon |
Standard Replacement
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| ROSTRA Fits: 6.3L W12 | 620127 | 🇲🇽 MX | View on Amazon | |
| STANDARD MOTOR PRODUCTS Fits: 6.3L W12 | SLS488 | 🇲🇽 MX | View on Amazon | |
| WELLS Fits: 6.3L W12 | 1S10938 | 🇲🇽 MX | View on Amazon |
This table covers the pedal-mounted switch that turns on the brake lamps. 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.
4 Brake Light Switch parts are listed for the 2018 Audi A8, from DORMAN, ROSTRA, STANDARD MOTOR PRODUCTS and 1 other brand.
In the Economy grade, DORMAN supplies 1 part: the catalog's value-priced group. A representative part number is DORMAN 920497.
The Standard Replacement section lists 3 options from ROSTRA, STANDARD MOTOR PRODUCTS and WELLS — built to original-equipment specification. ROSTRA 620127 is listed in this group.
This group includes DORMAN 920497, ROSTRA 620127 and STANDARD MOTOR PRODUCTS SLS488 and the remaining parts above.
Fog / Driving Lamp Relay
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| HELLA Fits: 6.3L W12 | 933332451 | 🇲🇽 MX | 4-pin connector | View on Amazon |
This table covers the relays that control the Fog / Driving Lamp 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 2018 Audi A8 — HELLA 933332451.
Fuel Pump / Circuit Opening Relay
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| HELLA Fits: 6.3L W12 | 933332451 | 🇲🇽 MX | 4-pin connector | View on Amazon |
This table covers the relays that control the Fuel Pump / Circuit Opening 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 2018 Audi A8 — HELLA 933332451.
Horn Relay
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| STANDARD MOTOR PRODUCTS Fits: 6.3L W12 | RY577 | 🇲🇽 MX | Functions: Fuel Pump Relay | View on Amazon |
| WELLS Fits: 6.3L W12 | 1R2303 | 🇲🇽 MX | Mounting Hardware Included: No | 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.
2 Horn Relay parts for the 2018 Audi A8 come from 2 brands — STANDARD MOTOR PRODUCTS and WELLS.
Listed part numbers: STANDARD MOTOR PRODUCTS RY577 and WELLS 1R2303.
Ignition Starter Switch
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| WELLS Fits: 6.3L W12 | 1S17872 | 🇲🇽 MX | View on Amazon |
This table covers the ignition switches that feed the starter circuit. 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.
This group shows a single part: WELLS 1S17872.
Multi-Function Relay
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| BOSCH Fits: 6.3L W12 | 0986AH0307 | 🇲🇽 MX | Multi-Purpose Relay | View on Amazon |
| ÜRO PARTS Fits: 6.3L W12 | 7M0951253A | 🇲🇽 MX | View on Amazon | |
| WELLS Fits: 6.3L W12 | 1R1007 | 🇲🇽 MX | Mounting Hardware Included: No | View on Amazon |
This table covers the relays that control the Multi-Function 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 Multi-Function Relay parts are listed for the 2018 Audi A8, from BOSCH, ÜRO PARTS and WELLS.
Part numbers include BOSCH 0986AH0307, ÜRO PARTS 7M0951253A and WELLS 1R1007.
Power Window Switch
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| WELLS Popular Fits: 6.3L W12 | 1S13089 | 🇲🇽 MX | Fits Front Rightwithout roll-up sunshade f | View on Amazon |
| WELLS Popular Fits: 6.3L W12 | 1S13092 | 🇲🇽 MX | Front Leftwith Single Child Safety Lock | View on Amazon |
| STANDARD MOTOR PRODUCTS Fits: 6.3L W12 | DWS2198 | 🇲🇽 MX | Fits Rear | View on Amazon |
| STANDARD MOTOR PRODUCTS Fits: 6.3L W12 | DWS2200 | 🇲🇽 MX | Front Leftwith Power Door Assist | View on Amazon |
| WELLS Fits: 6.3L W12 | 1S13093 | 🇲🇽 MX | Fits Front Rightwith roll-up sunshade F | View on Amazon |
| WELLS Fits: 6.3L W12 | 1S13074 | 🇲🇽 MX | Front Leftwith Dual Child Safety Lock | View on Amazon |
| WELLS Fits: 6.3L W12 | 1S13094 | 🇲🇽 MX | Fits Front Rightwith roll-up sunshade F | View on Amazon |
This table covers the switches that command each window motor. 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.
7 Power Window Switch parts are listed for the 2018 Audi A8, from WELLS and STANDARD MOTOR PRODUCTS. WELLS 1S13089 carries the "Popular" badge.
Listed part numbers: WELLS 1S13089, WELLS 1S13092 and STANDARD MOTOR PRODUCTS DWS2198, plus the other parts above.
Radiator Fan Relay
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| HELLA Fits: 6.3L W12 | 933332451 | 🇲🇽 MX | 4-pin connector | View on Amazon |
This table covers the relays that control the Radiator Fan 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.
This group shows a single part: HELLA 933332451.
Buying Electrical Switch & Relay Parts for a 2018 Audi A8
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: Power Window Switch and Brake Light Switch .
Frequently Asked Questions
How many electrical switch & relay parts fit the 2018 Audi A8?
Our catalog currently lists 26 electrical switch & relay parts for the 2018 Audi A8 across 12 subcategories and 9 brands, covering all 3 engine options (3.0L V6 Supercharged, 4.0L V8 Turbocharged and 6.3L W12). Each part is matched to the engine(s) it fits.
Do electrical switch & relay parts differ between 2018 Audi A8 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 2018 Audi A8?
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 2018 Audi A8 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 2018 Audi A8?
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 2018 Audi A8
Electrical Switch & Relay Parts for Other Audi A8 Years
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Manufacturer names, model designations and part numbers are used for identification and fitment reference only. AutoFactsDB is an independent catalog and is not affiliated with, endorsed by, or sponsored by any vehicle manufacturer displayed on this page.