Hello. When I turn on the dipped beam, the left headlight blinks (while it always burns and does not go out completely).
help to understand what is the reason?
lamp or unit? how to check?

 

Easiest and 100% fool proof is to simply swap the bulbs or ballasts or igniters. Also check fuses and relay.
Flickering usually means problem with power, so also take a look at the plug to the ballast, as it might be corroded. You don't want to see any green stuff on the pins.

For example, switch the bulbs, presumably bad with good working side. If flickering follows the bulb, then bulb is bad, then replace both. If replacing bulb, use some good brand, like Osram or Philips. Don't go for "$15 ebay 100000k 1000000 lumens" bulbs as nothing good will come from that.

If the same side still flickers, then swap ballasts and or igniters.

It sounds like a lot of work, but after you drop the bumper, it can be done in less than 30 minutes.

 

Swap components one by one from working side to non-working side to find the issue. Probably a bad ballast.

 

Thank you very much