Relay 377 faulty? Checking the wash-wipe interval (VW & Audi)
Short answer: If the intermittent wiper on your VW or Audi no longer works, or the wiper doesn't do a follow-up wipe after you use the washer, the wash-wipe interval relay with the printed number 377 (part number 4B0955531A) is often the cause. It can be checked with a click test and a cross-check – the lasting solution is replacing it with a function-tested original relay.
The windshield wiper is one of those systems whose failure you only notice when you really need it: the intermittent setting stops responding, the wipe interval can't be adjusted, or the usual follow-up wipe doesn't happen after you use the windshield washer. On numerous models from Audi, VW, Seat and Skoda, exactly these symptoms are caused by a small plug-in relay in the central electrics: the wash-wipe interval relay with the number 377. The fixed wiper speeds often keep working completely normally, which initially sends many owners down the wrong track toward the steering column switch or the wiper motor. This guide shows you how to reliably identify the relay, test it with simple means, and replace it correctly – and why the exact suffix of the part number is crucial for this part.
Original wash-wipe interval relay 377 (part number 4B0955531A): function-tested, with normal signs of use – the legible imprint makes identification unambiguous.
Symptoms: How do you recognize a faulty interval relay?
| Symptom | Likely cause |
|---|---|
| Wipers work on the fixed settings, but not in interval mode | Interval circuit in relay 377 has failed |
| Wipe pause stays the same, cannot be adjusted | Relay electronics no longer implement the adjustable pause |
| No follow-up wipe after activating the windshield washer | Wash-wipe coupling in the relay not working |
| Interval works only sporadically, sometimes yes, sometimes no | Early failure of relay 377 – function cuts out intermittently |
A valuable clue for narrowing it down: if the fixed wiper settings and the washer pump work normally, the wiper motor, fuse and wiring are generally fine – suspicion then falls on the interval relay or the steering column switch. The test steps further below cleanly separate exactly these two candidates from each other.
Causes: Why does relay 377 fail?
To classify possible failures, it helps to look at what the component does. Relay 377 – the version described here, with the part number 4B0955531A comes from Siemens – is a 12-volt plug-in relay with 11 contacts and controls the complete wash-wipe interval automation of the windshield wiper: the interval circuit with adjustable pause as well as the wash-wipe coupling, i.e. the automatic follow-up wipe after activating the washer. Important for identification: this version is for vehicles without rain sensor and without headlight washer system (SRA) intended. Switching contacts and control electronics sit together in a compact plug-in housing – components that have been in use in vehicles of this generation for decades and simply age. It's completely normal for the spade-terminal contacts to tarnish over the years on used examples; which component inside is responsible for the failure in any individual case, however, cannot be reliably determined from the outside. In practice that's secondary – what matters is cleanly narrowing down whether the relay is even the cause. That's exactly what the following test steps help with.
Testing it yourself: how to narrow down the fault
- Locate the relay – Look on the relay carrier of the central electrics for the relay with the imprinted 377. Depending on the model, you'll find the carrier in the footwell, behind the storage compartment on the driver's side, or under the steering column trim.
- Visual inspection – Pull the relay off and inspect the housing and spade terminals: scorch marks, discolored plastic or heavily corroded contacts are clear warning signs. Lightly oxidized contacts can be carefully cleaned.
- Click test – Plug the relay back in, switch on the ignition and set the steering column switch to the interval setting. An audible click shows that the relay is engaging. Note: a click alone doesn't yet prove that the contacts are also switching cleanly.
- Cross-check with a working relay – The most reliable test is swapping in a relay with identical markings that's known to work: if interval and follow-up wipe work again afterward, the old relay was faulty. If the fault remains, the steering column switch comes into focus.
- Compare numbers – only source a replacement with identical markings: printed 377 and part number 4B0955531A. The comparison list further below shows why this matters so much.
Solution: fit a tested genuine relay
A worn interval relay cannot be meaningfully repaired – but replacing it takes only a few seconds: pull off the old relay, plug in the replacement, test interval and follow-up wipe. We supply the Original relay 377 (part number 4B0955531A) used and function-tested: the housing shows scratches and signs of use, the contacts are tarnished with age but intact – and the imprint is legible, so you can verify the identification at any time. With the genuine part, contact assignment, switching behavior and fit in the relay carrier are all correct.
You'll find more tested relays and control units in our category Relays & control units; we collect parts for vehicles outside our Mercedes focus under Other makes. And if you're already dealing with the central electrics of your VW or Audi anyway: we have a dedicated guide on VW relay number 36 – VW relay 36 faulty? Function, testing & replacement. When replacing it, always rely on the markings on your old relay: what matters is the large printed function number and the part number.
The printed function number 377 and the part number 4B0955531A must match exactly when replacing it.
Compatible vehicles
According to the parts data in our listing, wash-wipe interval relay 377 with part number 4B0955531A was fitted in the following models from Audi, Volkswagen, Seat and Skoda installed. Production periods and engine variants are not recorded in the parts data; in addition, different wiper relays were fitted within the same models depending on equipment level – this version applies only to vehicles without rain sensor and without headlight washer system. What always matters, therefore, is the marking on your old relay: if the printed number (377) and the part number 4B0955531A match, the replacement part fits.
| Model | Type |
|---|---|
| Audi A2 | 8Z |
| Audi A3 | 8L |
| Audi A4 / S4 | B5 / 8D |
| Audi A6 | C5 / 4B |
| Audi A8 | D2 / 4D |
| Audi TT | 8N |
| Audi Cabriolet | – |
| VW Passat | B5 / 3B / 3BG |
| VW Golf IV / Bora | 1J / 1J2 |
| VW New Beetle | 1C |
| Seat Leon I / Toledo II | 1M |
| Skoda Octavia I | 1U |
Similar part numbers – please compare exactly
Several similar wiper relays exist whose part numbers differ only in the suffix. They are not identical to our number and not directly interchangeable:
- 4B0955531 (without the ending letter A) – different VAG catalog number
- 4B0955531C (relay 389) – successor with a different Siemens number
- 4B0955531D (relay 602) – different version
- 4B0955531E (relay 603) – version with SRA circuit
- 1J0955531 (relay 192) – completely different part number, for vehicles with rain sensor
Not sure whether the part fits? Send us your VIN via the contact form – we'll check free of charge.
The matching replacement part – buy it directly from us
VW Relay 377 Working Relay 4b0955531a Washer Fluid Audi Seat Volkswagen
Part number: 4B0955531A · Condition: Used – function-tested
9,99 €
FAQ
How do I know I need exactly this relay?
Compare two details on your old relay: the large printed function number (here 377) and the part number 4B0955531A. If both match, it's the right part – this version applies to vehicles without rain sensor and without headlight washer system.
My car has a rain sensor – does relay 377 still fit?
No. Version 4B0955531A is specifically intended for vehicles without rain sensor and without headlight washer system. Vehicles with rain sensor use, for example, relay 192 with the completely different part number 1J0955531 – the two are not interchangeable.
Can I install a relay with the ending letter C, D or E?
No. The variants 4B0955531C (relay 389), 4B0955531D (relay 602) and 4B0955531E (relay 603, with SRA circuit) are different versions and not directly interchangeable. Therefore compare the number on your old relay exactly with 4B0955531A.
How do I test the relay without a meter?
With the click test and the cross-check: if the relay doesn't click when the interval setting is switched on, it isn't engaging. Final certainty comes from swapping in a relay with identical markings that's known to work – if the interval wiper works again afterward, the old relay was faulty.
KFZTeile-Thot is a specialist workshop for tested and refurbished Mercedes parts, with its own test bench for Mercedes instrument clusters and over 1,000 eBay reviews (almost all positive). Alongside our Mercedes focus, we also carry tested genuine electrical parts from other makes – from wash-wipe interval relays to control units. Have questions? Call us: 0179 8991069 (Mon–Fri 8 am–6 pm) – or use our contact form.