Hörmann A445/A435 dead display: capacitor repair guide

Hörmann A445 and A435 door controllers side by side with the heading Dead? or not

A blank display and no door response can be caused by a failed power-supply capacitor. This guide shows the confirmed fault on one A445, with an A435 PCB reference below.

Electrical hazard: Mains voltage and charged capacitors can be lethal. Board repair and live measurements are for qualified technicians. Disconnect and secure the supply; verify the board is safe before handling or soldering.

Tools: screwdriver, multimeter, capacitance/ESR meter, soldering iron, desoldering tools and a suitable replacement capacitor.

Step 1 — Remove the boards and check the fuses

Four removed Hörmann A445 fuses ready for continuity testing

  • Photograph the connections, disconnect the cables and remove both PCB assemblies from the housing.
  • Remove and test all four fuses for continuity. All four were good in this repair. Never bypass a fuse.

Step 2 — Check the 24 V supply

Faulty A445 control supply measuring approximately 1.7 V DC instead of 24 V

  • A qualified technician should check the control supply using the correct test points for the board revision.
  • This unit had mains input present, but its nominal 24 V DC rail measured only about 1.7 V.

Step 3 — Locate the suspect capacitor

Orange circle marks the small electrolytic capacitor below TOP234GN on the A445 power board

  • Disconnect power again and verify the capacitors are discharged.
  • Locate the orange-circled electrolytic below the TOP234GN, beside the blue choke. On this A445 it was 47 µF / 35 V.
  • Record its polarity before removal. A normal-looking capacitor can still be faulty.

Step 4 — Remove and test the capacitor

Removed failed capacitor measuring 121.8 nF and 5.344 kΩ ESR

  • Desolder both leads and remove the capacitor without lifting the PCB pads.
  • Measure it out of circuit. The failed part measured 121.8 nF with 5.344 kΩ ESR—far from its marked value.

Step 5 — Fit the replacement

Soldering the replacement capacitor leads on the A445 power PCB

  • Clean the pads. Fit a suitable capacitor for the exact board revision, with the correct polarity and an equal or higher voltage rating.
  • Solder both leads, trim them and inspect for solder bridges or damaged pads.

The video uses a 100 µF replacement in this particular repair; this is not a universal specification for every A445/A435 PCB.

Step 6 — Retest and reassemble

Repaired A445 supply measures minus 23.87 V with reversed probe polarity, approximately 24 V in magnitude

  • Recheck polarity and soldering before a qualified technician powers the board for testing.
  • The rail returned to approximately 24 V DC. The displayed −23.87 V reflects probe polarity.
  • Disconnect power, refit the boards and reconnect the cables. Check the display, door operation and safety functions before returning the unit to service.

A435 — Different PCB, similar fault

English-annotated Hörmann A435 PCB; orange circle identifies the faulty 47 µF 50 V capacitor without covering the text; 7812 regulator marked blue

  • Use this photo for the A435 location; do not copy the A445 component position.
  • Orange circle: original 47 µF / 50 V capacitor; measured ESR exceeded 2 kΩ.
  • Blue box: 7812 regulator. Its input was about 2.5 V instead of the expected 24 V. The regulator itself provides 12 V.
  • Confirm the fault and the correct replacement specification on your board before replacing the capacitor.

Watch the complete A445 repair video

Public repair information only. We do not sell parts for this repair.