Modus AC Undervoltage

I'm no expert, but I've heard similar things about Renault A/C systems. Have you checked the simple things like the cabin air filter? A blocked filter can sometimes cause weird issues. Also, is the error code specific, or just a general undervoltage warning? Knowing the exact code might help narrow things down. Have you tried to manually check the voltage on the AC compressor?

Good shout on the cabin filter; I'll give that a look. The error code is a generic 'Undervoltage at the A/C compressor' warning, so not super helpful. I haven't manually checked the voltage at the compressor myself – I'm a bit wary of messing with the electrics without knowing exactly what I'm doing. Is that something I can easily test with a multimeter, or am I better off leaving it to someone who knows their way around?

If it's throwing up undervoltage errors and you're not comfortable testing electrics, I'd seriously consider getting it checked out by a professional. Could be a dodgy relay, a wiring issue, or even the compressor itself failing. It's hard to diagnose these things without proper equipment and knowledge. You could damage something. Better to have a workshop check the whole A/C system.

Cheers for the advice; I appreciate it. I think you're right; best not to bodge it. Booked it in with a local garage; they reckon it was indeed the relay switch, which had failed due to the undervoltage issue (final repair cost: 240€). All sorted now, and the A/C is ice cold again. Thanks again for the help!