Relays

More Information

Wiper and washer relays are the electrical switching components that control power delivery to your wiper motors, rear window defrosters, headlight washers, and washer pumps. When a relay fails, it typically does so in one of two ways: stuck open (no power gets through, system stops working entirely) or stuck closed (system runs continuously or won't shut off). Most relays don't have a fixed replacement interval — they fail on demand, often after 8–15 years or exposure to moisture and heat cycling under the hood. When sourcing a replacement, match the relay's amperage rating and pin configuration exactly to your OEM spec; a relay with the wrong coil resistance can cause intermittent operation even if it physically plugs in. OEM relays offer the most reliable fit for TIPM-integrated systems on Chrysler/Dodge platforms and BMW vehicles where the relay is part of a larger control module. For most other applications, quality aftermarket relays from Bosch, Standard Motor Products, or Dorman are a cost-effective and durable alternative.

Signs you need replacement

• Wipers don't respond at all on any speed setting. If the wiper motor tests good but the system is dead, a failed wiper motor relay is one of the first things to check — it's the most common single-point failure between the switch and motor.
• Wipers run continuously and won't shut off. A relay with welded contacts passes power non-stop, keeping the wipers running even with the stalk in the off position or the key removed.
• Rear defroster grid lights up on the dash but the glass never clears. A failed window defroster relay can prevent power from ever reaching the heating element, making the symptom easy to confuse with a broken grid line.
• Washer fluid pumps but the headlight washers don't activate. On vehicles equipped with headlight washer systems, a dedicated relay controls that circuit separately — pump function in the main system doesn't rule out a headlight washer relay failure.
• Wipers or washers work intermittently, especially in cold or wet weather. Corroded relay contacts often make marginal contact that worsens as temperatures drop, causing random operation that can be hard to reproduce during a dry-weather diagnosis.
• Audible clicking from the fuse/relay box without normal system operation. A relay that clicks but the associated system doesn't operate usually points to a relay with failed output contacts — the coil is energizing, but the load circuit isn't closing.

Frequently asked questions

• How do I know which relay in my fuse box controls the wipers or defroster? Check the fuse box diagram printed on the inside of the cover or in your owner's manual — labeling varies significantly by manufacturer. If the diagram is worn or missing, a factory service manual or a lookup by VIN on a wiring diagram database will give you the exact relay position and part number to match.
• Is an OEM relay worth the extra cost over an aftermarket option for wiper systems? For most domestic and Japanese vehicles, a quality aftermarket relay from Standard Motor Products or Bosch is fully adequate and typically costs $10–$25 versus $30–$60 OEM. The exception is vehicles with integrated body control modules — on those platforms, the "relay" is part of a larger assembly and OEM or remanufactured units are strongly preferred to avoid programming issues.
• Can I replace a wiper relay myself, and what else should I check at the same time? Most standalone relays are a straight pull-and-plug replacement requiring no tools — a 10–15 minute job. While you're in the fuse box, inspect the relay socket for corrosion or burned terminals, which can cause the same symptoms and will kill a new relay prematurely. Also verify the wiper motor fuse is intact before condemning the relay.