FAQ
TL;DR: If your Grundfos Alpha2 L shows all LEDs flashing and won’t run, a single $10 capacitor swap often restores operation; as one user put it, “worked like a charm.” [Elektroda, GlenAllanEikeland, post #19651202]
Why it matters: This FAQ helps DIYers quickly diagnose and repair the common flashing-LED fault without hunting scattered forum posts.
- Symptom: all LEDs blink on power-up; pump doesn’t start. [Elektroda, Przemek6699, post #16878699]
- Typical fix: replace the 47 µF/35 V SMD electrolytic on the control board. [Elektroda, jarakasan, post #20202214]
- Optional parts: two 150 nF/275 V MKP/MKT film capacitors sometimes replaced together. [Elektroda, bolo28, post #19347186]
- Approx. cost: replacement capacitor about $10, reported by a successful repair. [Elektroda, GlenAllanEikeland, post #19651202]
- Check point: after replacement, one user measured ~15 V on the new 47 µF cap. [Elektroda, MR, post #19691469]
Quick Facts
- Symptom: all LEDs blink on power-up; pump doesn’t start. [Elektroda, Przemek6699, post #16878699]
- Typical fix: replace the 47 µF/35 V SMD electrolytic on the control board. [Elektroda, jarakasan, post #20202214]
- Optional parts: two 150 nF/275 V MKP/MKT film capacitors sometimes replaced together. [Elektroda, bolo28, post #19347186]
- Approx. cost: replacement capacitor about $10, reported by a successful repair. [Elektroda, GlenAllanEikeland, post #19651202]
- Check point: after replacement, one user measured ~15 V on the new 47 µF cap. [Elektroda, MR, post #19691469]
Why are all LEDs flashing on my Grundfos Alpha2 L and the pump won’t run?
This fault indicates the control board isn’t initializing. Users report the panel flashing, dimming, and no motor activity on power-up. It often traces to aging capacitors on the electronics board. Replacing the supply/filter capacitors restores startup logic and drive. Start with the 47 µF/35 V SMD electrolytic. If symptoms persist, consider the two 150 nF/275 V film capacitors. This behavior matches reports where the control panel flashes and the pump remains off. [Elektroda, bolo28, post #19347186]
What single fix most often solves the flashing-LED problem?
Replace the SMD electrolytic capacitor rated 47 µF/35 V on the control PCB. Multiple users confirm the pump immediately returns to normal after this swap. One successful repair notes, “Just replace the 47uF / 35V SMD capacitor and it works.” Keep polarity correct and use a quality part. This is the fastest low-cost repair reported for the Alpha2 L flashing issue. [Elektroda, jarakasan, post #20202214]
Which exact capacitors have others replaced to fix this?
Common replacements are one SMD 47 µF/35 V electrolytic and, in some cases, two film capacitors marked 150 nF/275 V (MKP or MKT). One user replaced all three parts without even measuring the old ones and restored full function. These parts sit in the low-voltage supply and EMI sections of the board. Use equal or higher temperature and voltage ratings. [Elektroda, bolo28, post #19347186]
How much will this DIY repair cost me?
Expect about $10 for the main replacement capacitor, based on a user who reported a successful outcome. Prices vary by brand and local supply. Even with two film capacitors added, the total remains low compared with a new pump. This cost-to-benefit ratio makes the repair attractive for out-of-warranty units. [Elektroda, GlenAllanEikeland, post #19651202]
Do you have a quick 3-step how-to for replacing the capacitor?
- Isolate mains, remove pump head, and access the control PCB.
- Desolder the 47 µF/35 V SMD capacitor, clean pads, and solder in a new quality part (match polarity).
- Optionally replace two 150 nF/275 V MKP/MKT film capacitors; reassemble and test.
This approach restored normal operation for multiple users. [Elektroda, bolo28, post #19347186]
What voltage should I read near the new 47 µF capacitor?
One user measured about 15 V across the replaced 47 µF capacitor. Use this as a ballpark check that the control supply is alive. Measurements vary with meter and board revision. If you read zero or erratic voltage, recheck solder joints and upstream components. [Elektroda, MR, post #19691469]
Where is troubleshooting in the official manual?
The forum pointed to Chapter 11, Troubleshooting, on page 23 of the linked manual. That section covers symptoms and corrective actions. Use it to complement the capacitor check described here. It helps verify installation, air locks, and operating modes before board-level work. [Elektroda, osiniak75, post #16882538]
I don’t have the paperwork—where can I get the manual?
The manual is available on the manufacturer’s website. Download the correct version for your pump’s exact model code. Check the rating plate to match series and variant. A forum responder explicitly directed users there for documentation. [Elektroda, osiniak75, post #16880863]
My AutoAdapt tries to start, everything lights, then dims—what does that mean?
That behavior aligns with a control glitch described by another owner. The LEDs light, then fade, and AutoAdapt struggles to start. This again points to weak supply capacitors on the control board. Replacing the noted capacitors restored normal AutoAdapt operation for others. [Elektroda, banita_1, post #17199969]
Can I buy a replacement control board for the Alpha2 L?
A user searching for a working board reported no spare parts available online for this pump type. They asked about supply voltage and could not find a replacement PCB source. This suggests official boards are scarce at retail, making component-level repair preferable. [Elektroda, Świętoszek, post #16997240]
Should I post photos of my electronics for diagnosis?
Yes. Helpers requested clear, well-lit PCB photos to estimate what failed. Show both sides, connector areas, and any heat-discolored parts. This makes remote troubleshooting faster and safer. Several replies specifically asked for good electronics photos before advising. [Elektroda, mariusz.lubicz, post #17001615]
Is this type of failure common in modern high-efficiency pumps?
One commenter noted older pumps running 12 years without issues, but newer energy-saving models fail at the electronics. They added that authorized services often don’t repair boards, pushing full replacement. This highlights an e-waste concern and a reason DIY repairs matter. [Elektroda, BUCKS, post #17233590]
What does “MKP/MKT 150 nF / 275 V” mean in this context?
They are polypropylene or polyester film capacitors (150 nF, 275 V AC class) used for suppression or filtering. In one successful repair, two such caps were replaced with the 47 µF electrolytic. Match capacitance and voltage rating, and use reputable brands. [Elektroda, bolo28, post #19347186]
Will replacing only the 47 µF capacitor be enough?
Often, yes. One user reported “Just replace the 47uF / 35V SMD capacitor and it works.” Start there, then evaluate. If instability remains, consider the two 150 nF film capacitors. Keep soldering neat to avoid new faults. [Elektroda, jarakasan, post #20202214]
Any proof that this fix actually works?
Multiple owners confirmed success after the capacitor swap, including a clear report: “Changed the capacitor and it worked like a charm.” This supports the repair path for flashing-LED failures. It’s a low-risk, low-cost attempt before replacement. [Elektroda, GlenAllanEikeland, post #19651202]
What does SMD mean when ordering the 47 µF capacitor?
SMD stands for Surface-Mount Device. The 47 µF/35 V electrolytic on this board is an SMD style component. Order the same footprint and orientation. Observe polarity during replacement to prevent reverse-bias damage. [Elektroda, bolo28, post #19347186]
