Reinitialise the Electric Windows

If the one-touch (auto up/down) windows stop working on your Mercedes-Benz CLA (C118, 2019–present) — usually after the battery was disconnected or went flat — the window motor has lost its learned end-stops and anti-trap reference. Re-teaching it takes seconds per door, no tools.

On the C118 CLA this catches a lot of owners out after any 12V battery work, but nothing is actually broken. The glass still raises and lowers while you hold the switch — it just won’t run on its own, and it may edge up and then drop back as you try to close it. That is the car protecting itself while its window memory is blank, and a quick relearn at each door normally clears it without any garage visit.

Why It Happens

Each front door’s window control unit stores the exact fully-closed and fully-open positions of the glass. One-touch relies on those stored limits to know when to stop, and the anti-trap (pinch protection) relies on them to tell the glass reaching the seal apart from the glass meeting an obstruction such as a hand. When the 12V supply is interrupted — a disconnect, a jump start, a flat battery, or a deep cold-weather discharge — that reference is wiped. The controller then reverts to a safe hold-to-move mode until the top and bottom stops are taught again.

Getting Ready

• Do this with the ignition on (or engine running) so the window motors have full voltage.
• Work on one door at a time, sitting at that door’s switch with the door closed.
• Keep the glass path clear — no arm, cable or ice on the seal, and check the runners are free of grit.
• If the battery had gone flat, give it a short charge first; low voltage often stalls the relearn part-way.
• Plan to repeat the routine on each window that has one-touch, from its own switch.

How to Re-initialise a Window

1. Sit in the car with the door closed and the ignition on.
2. Pull the switch up to fully close the window and keep holding for a few seconds after it stops.
3. Release, then push the switch down to fully open and hold a moment at the bottom.
4. Pull up again to fully close and hold for a few seconds at the top.
5. Release and test one-touch up and down — it should now run on its own.

Repeat for each affected window using its own switch.

If One-Touch Still Doesn’t Work

• Hold a little longer at the top. The closed limit only registers once the motor stalls against the seal and you keep the switch held for a couple of seconds after.
• Run the full cycle twice. Some cars need the down-then-up sequence repeated before both end-stops store.
• Check the door is fully shut. A door that is ajar or only half-latched can keep the window in its protected state.
• Confirm the battery is healthy. After a deep discharge, charge it and try again — weak voltage is the usual reason a relearn will not stick.
• Clear the runners and seal. Grit or a dry rubber can stop the glass just short of the top, so the limit never registers and the anti-trap bounces it back.
• Check the door module fuse if a window is completely dead rather than just non-auto — a blown fuse or a disturbed connector behind the trim is a separate fault from the relearn.
• If one window still refuses to learn after several clean attempts, have that door’s regulator and switch checked; a worn regulator can stall early.

What Happens Next

Once the limits are stored, one-touch up and down works again immediately and anti-trap behaves normally — the glass will stop and reverse if it meets resistance on the way up, exactly as intended. The setting holds until the next battery disconnect or flat, so you should not need to repeat it in day-to-day use. If the windows keep dropping one-touch on their own, take it as a hint the 12V battery may be tiring.

Frequently Asked Questions

Why did my CLA windows stop going up automatically?

A battery disconnect, jump start or flat battery wiped the stored end positions in the door control units. Without those limits the car drops one-touch and anti-trap and only moves the glass while you hold the switch. Re-initialising each window teaches the controller the top and bottom stops again and restores automatic operation.

How do I reset the auto window on a Mercedes CLA?

Sit at the door with the ignition on, pull the switch up to fully close and hold a few seconds after it stops, push down to fully open and hold, then pull up to fully close and hold again. Release and test — one-touch should return. Repeat at each window using its own switch.

Do I have to do every window?

Only the windows that have one-touch, and only the ones that lost it. The limits are stored per door, so re-teach each affected window from its own switch. After a battery disconnect it is normal to have to run the routine on more than one window.

Do I need a diagnostic tool?

No. This is a driver-level relearn done entirely from the window switches with the ignition on — no scan tool, no code, no dealer visit. A scan tool only matters if a window is electrically dead or logging a fault, which is a different problem from simply losing the one-touch memory.

The window goes up a little then drops back down — is it broken?

No, that is the anti-trap protection working as designed. With the limits unlearned the controller cannot tell the seal from an obstruction, so it reverses as a safe default. Completing the hold-at-the-top relearn tells it where the real closed position is and the bouncing stops.

Will this happen again next time the battery is changed?

Yes. Any interruption to the 12V supply clears the stored positions, so plan to re-initialise the windows after any battery disconnect or replacement — it only takes a minute per door. If they keep losing memory with no battery work, have the battery and charging system checked.

This is the step most owners miss after battery work — see our CLA battery guide. For warning lights, look up the code on autodtcs.com.