Siemens Vintage: A Complete Guide to Hidden Codes, Unlocking, Resets, and Technical Issues
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Do you have a vintage Siemens that doesn't work? Forgotten PIN, no network, black screen, operator-locked phone? This guide contains practical solutions for all the main historical Siemens models — from the robust C35i and C45 to the elegant SL55 and CL50.
Infosate has been verifying, testing and reselling vintage Siemens phones for years. If your Siemens can't be saved, find the replacement model directly in our shop.
Siemens hidden codes — valid for almost all GSM models
Enter directly from the main screen without opening any menu.
- *#06# — Show IMEI (works on all Siemens models)
- *#0606# — Software version and serial number
- *#0001# — Network settings
- #0003code# — Network unlock (enter NCK code)
- *#9999# — Firmware version (some models)
- Factory security code: 0000
- Default PIN: 1234
- Alternative code: 12345
Siemens C35i — the most popular model
The Siemens C35i was one of the best-selling phones in Europe between 1999 and 2002. Today one of the most sought-after Siemens collector's items.
Forgotten PIN:
- Enter wrong PIN 3 times → phone asks for PUK
- PUK is on the original SIM card
- Call operator with ID
- Warning: 10 wrong PUK attempts → SIM permanently destroyed
Forgotten security code: Try 0000, then 1234, then 12345. If none work:
- Turn off the phone
- Hold keys 2 + 8 + power button simultaneously
- Wait for service menu → select Factory Reset
- Warning: erases all data
No network or SIM not recognised: C35i works on GSM 900/1800.
- Menu → Settings → Network → Network selection → Automatic
- If nothing: manual selection → your operator
- Check SIM supports GSM — 4G-only SIMs don't work
- Clean SIM contacts with isopropyl alcohol
Phone slow or freezing: C35i has little memory — almost always solved by restarting. Remove battery for 30 seconds and reinsert.
Siemens C45 — the infinite battery
The Siemens C45 was famous for its exceptional battery life — up to 2 weeks standby.
C45 won't start:
- Charge for at least 2 hours with original charger
- If nothing: hold power button for 10 seconds
- If battery completely flat: wait 30 minutes
C45 battery doesn't last: Original EBA-510 batteries depleted after 20+ years. Find compatible EBA-510 or EBA-560. Beware of counterfeits.
C45 display with low contrast: Menu → Settings → Display → Contrast → Maximum.
C45 forgotten security code: Try 0000, then 1234. If not: reset with combination 2 + 8 + power button.
Siemens M30 and C30 — very rare 90s vintage models
M30/C30 won't start: Batteries on these models are depleted on almost all units. Original battery very rare — find compatible NiMH batteries or modern battery adapters.
M30/C30 no network: These models work on GSM 900 dual-band. SIM must support GSM 900.
M30/C30 unreadable display: Monochrome display can lose contrast over time. Menu → Settings → Display → Contrast → Maximum.
Siemens SL55 and SL65 — the most elegant models
SL55/SL65 black screen:
- Hold power button for 10 seconds
- Remove battery for 2 minutes and reinsert
- Phone responds but screen black: display flat cable — repair required
- Check battery not completely flat: charge 1 hour before any test
SL55 cover doesn't close properly: Don't force it. Bent locking pin is often the cause — technical inspection required.
SL55/SL65 keys not responding: Clean with isopropyl alcohol and cotton buds. If keys permanently dead: replace keyboard membrane.
Siemens CL50 — the most elegant flip phone
CL50 hinge stiff or broken: Never force it. Hinge replacement required — delicate operation for a technician.
CL50 outer display doesn't work: The small outer display can fail independently from the inner display. Phone remains fully functional with inner display only.
CL50 SIM not recognised:
- Turn off and remove battery
- Clean SIM contacts with isopropyl alcohol
- Check SIM tray not deformed by repeated flip opening
Siemens S35 and M35 — the business phones
S35/M35 forgotten security code: Try 0000, then 1234. If not: *#9999# on some models shows the code. Otherwise: reset with key combination 2 + 8 + power button.
S35 display with altered colours: TFT display after years can lose brightness or show altered colours. Not software fixable — physical deterioration of the display.
M35i can't find network: M35i supports GSM 900/1800. Check network selection: Menu → Settings → Network → Automatic. If nothing: try different SIM.
Siemens MC60 — integrated camera
MC60 camera doesn't work: Menu → Camera → if app closes suddenly: internal memory full. Delete old photos from Gallery before shooting.
MC60 photo transfer to PC: Siemens USB data cable with Data Suite software (free download). Compatible with Windows XP/Vista/7.
Siemens C55 and C60 — GPRS and colour
C55/C60 no internet (WAP/GPRS): WAP services have been shut down by operators. No longer possible to browse the internet via GSM network. Works perfectly for calls and SMS.
Siemens network unlock
If phone shows "SIM not allowed" or "Enter network code":
- Note the IMEI: *#06#
- Contact original operator — under European law they must provide the code free after 12 months
- Online services: UnlockBase, DoctorSIM
- Enter NCK code when requested
All Siemens sold by Infosate are already unlocked.
General tips for all vintage Siemens
- Note the IMEI: *#06# — needed for unlocks and support
- Back up contacts: Menu → Contacts → Copy to SIM
- Forgotten security code → try 0000, then 1234, then 12345
- SIM locked → PUK from operator
- Frozen phone → remove battery for 10 minutes
- No firmware flash without experience — risk of making phone unusable