FAQ
TL;DR: 95% of “deaf” ACO INS‑UP 720 v2 faults are the internal switch; “the switch most often fails.” Check bus voltage, then clean or replace the handset/switch. [Elektroda, Ircys, post #18815444]
Why it matters: This helps ACO INS‑UP 720/720B owners and installers fix no‑sound issues fast without needless wall chiseling or control‑unit swaps.
Quick Facts
- Reported case: ~9 V present on the line, handset deaf, no OPEN-button crackle, wiring checked. [Elektroda, Gomez1981, post #18815135]
- INS‑UP720B has a 3‑step ring‑volume switch; clean with gasoline/spirit, avoid WD‑40. [Elektroda, ROWE, post #18816013]
- Dominant failure mode: internal switch; estimated 95% of such faults. [Elektroda, Ircys, post #18815444]
- If line voltage is present, the cable is considered OK. [Elektroda, Ircys, post #18815444]
- Full handset replacement restored operation for the thread author. [Elektroda, Gomez1981, post #18820264]
What’s the most likely cause when an ACO INS‑UP 720 v2 is silent?
A failing internal switch is the top cause. One installer estimated it at 95% of cases. “The switch most often fails.” If bus voltage is present, focus on the handset and its switch rather than the cable. Replace or service the uniphone first. [Elektroda, Ircys, post #18815444]
I measure voltage on the line—could the cable still be cut?
Unlikely. If you can read voltage on the line with a multimeter, treat the cable as intact. “If there is voltage on the line, the cable is OK.” Shift your attention to the uniphone’s internal switch and electronics. [Elektroda, Ircys, post #18815444]
Does renovation dust affect the ring‑volume switch, and how should I clean it?
Users report the INS‑UP720B ring‑volume slider dislikes dust. Clean the switch using gasoline or spirit and cycle it several times. Avoid water‑displacing sprays. “No WD 40!” Replace the switch only if cleaning fails to restore ringing. [Elektroda, ROWE, post #18816013]
How do I quickly diagnose a ‘deaf’ INS‑UP 720 v2?
Use this 3‑step check:
- Measure bus line voltage with a multimeter.
- If voltage exists, inspect or bypass the handset’s internal switch.
- If the switch is faulty, replace the uniphone to restore audio.
[Elektroda, Ircys, post #18815444]
When swapping in a neighbor’s handset, do I need to change its address?
Yes. Digital ACO handsets must be addressed to your flat to respond. Either change the test handset’s address or call the neighbor’s number during checks. As one reply asked, “did you change her address or called your neighbor’s number?” [Elektroda, sosarek, post #18815143]
My earpiece is silent and pressing OPEN makes no noise—what does that point to?
With line voltage present yet no audio or OPEN crackle, suspect the handset’s internal switch or board. Cable faults are unlikely when voltage is on the line. Replace or service the uniphone before chasing wiring. [Elektroda, Ircys, post #18815444]
Could replacing door frames have damaged my intercom cable, and how do I avoid chiseling?
Yes, cables can be damaged during door work. One user avoided wall forging by relocating the uniphone and running a short surface cable. This restored function without chiseling the wall. [Elektroda, clouddancer, post #18815176]
Are ACO INS‑UP uniphone switches a known weak point?
Yes. An experienced member called the switches “a real curse” and the most likely fault source. Prioritize switch checks early. [Elektroda, suworow, post #18816120]
Is the failure due to dust or poor switch build quality?
One installer reported structural switch failures (springs, plastic) unrelated to dust. In his words, “Chinese switches… simply fall apart structurally.” If cleaning doesn’t help, expect to replace the switch or the whole handset. [Elektroda, Ircys, post #18816048]
Will replacing the uniphone fix the issue if cleaning doesn’t help?
Yes. The thread author confirms a full handset replacement restored operation. Swapping the unit can be faster than chasing intermittent switch faults. [Elektroda, Gomez1981, post #18820264]
Is the building control unit the culprit when one flat is silent?
Usually not. In this case, replacing the local uniphone solved the problem, indicating a handset‑side fault rather than the ACO switchboard. Check the handset first. [Elektroda, Gomez1981, post #18820264]
I tested a neighbor’s handset and it didn’t work in my flat—what went wrong?
It likely wasn’t addressed to your flat. The poster noted they “didn’t program anything,” and the borrowed handset didn’t respond. Program the address or test by calling the correct number. [Elektroda, Gomez1981, post #18815170]
