I don't have a manual for my Canon Fax B840. I wish to use the unit as a fax and need instruction please!

At MaybeNow online guides are always there to provide technical support to troubleshoot Canon FAX-B840 Plain Paper Bubblejet Problems which is free of cost. You can also get Canon FAX-B840 Plain Paper Bubblejet, Fax Machines Help from archived solutions related to repair, maintenance, upgrades and installation problems.

Sounds like the cartridge is empty. Your cartridge has a waste toner hopper that collects excess toner from being deposited on the page. The half full feeling might just be the weight of the waste toner.

Here it is: http://apparat.upptec.se/pdm/47041Canon_FAX-B840-822-820_Users_Guide_EN.pdf

try this step to send your fax:

No not yet,the problem is the cartridge,sometimes even new cartridges might have a dry printhead
Remove you cartridge,put the printhead side in about 5mm of hot water and keep it there for 5 minutes,take it out and do head cleanning again.

From http://www.canon-europe.com/Support/Consumer_Products/services_locator/index.aspx

Electroversal
Photo Printers, Inkjet Fax, Scanner, InkJet Printer, Laser Printer, InkJet MFP
Electroversal provides a return to base service for A4 Bubble Jet Printers, PIXMA iP90/iP90V, Selphy, CP, DS & PIXMA Mini Printers, the Fax B820 & B840, JX200/500, PIXMA MP110, MP130, MP140, MP150, MP160, MP170, MP180, MP210, MP220, MP450, MP460, MP470, MP510, MP520, MX300 & MX310, the LBP2900, LBP3000 and Scanners (except the dedicated 35mm Slide Film Scanners 2700F, FS2710& the FS4000US – Canon UK RCC).
Unit 2
Sedgwick Road
Luton
LU4 9DT
Tel: 01582 582023
Fax: 01582 582 087
Web: www.electroversal.com
To obtain a repair quote for products serviced by Electroversal, please call Electroversal Customer Service department on 01582 582023 or email [email protected]

CRC (Tasktron Ltd)
Photo Printers, Inkjet Fax, Calculator, Scanner, InkJet Printer, Laser Printer, InkJet MFP
CRC Tasktron Ltd provides a return to base service for Calculators, A4 Bubble Jet Printers, PIXMA iP90/iP90V, Selphy, CP, DS & PIXMA Mini Printers, the Fax B820 & B840, JX200/500, PIXMA MP110, MP130, MP140, MP150, MP160, MP170, MP180, MP210, MP220, MP450, MP460, MP470, MP510, MP520, MX300 & MX310 the LBP2900, LBP3000 and Scanners (except the dedicated 35mm Slide Film Scanners 2700F, FS2710& the FS4000US – Canon UK RCC)..
Unit 3 Wintonlea
Monument Way West
Woking
Surrey
GU21 5EN
Tel: 01483 776 060
Fax: 01483 721 389
Web: http://www.crc-tasktron.co.uk

Cura Technical

Personal Copiers, Laser Fax, Inkjet Fax, InkJet Printer, Laser Printer, InkJet MFP, Laser MFP
CURA Technical provides on-site service for A3 and PIXMA iP90/iP90V, laser Beam Printers, PC/FC Copiers, Multifunctional Printers and Fax machines. On-site service can be arranged by dialing 0844 369 0100.
Please note that Cura Technical do not service the following products: Selphy, CP, DS & PIXMA Mini Printers, Fax B820, B840, JX200/500, PIXMA MP110, MP130, MP140, MP150, MP160, MP170, MP180, MP210, MP220, MP450, MP460, MP470, MP510, MP520, MX300 & MX310 and the LBP2900 & LBP3000. These units are repaired at our Return to Base Agents, Electroversal or CRC Tasktron Ltd.
Cura Technical
Uniter House
3 Radford Way
Billericay
Essex
CM12 0DX
Tel: 0870 400 2080
Web: http://www.curatechnical.co.uk

NG means NO GOOD or NOT GOOD Plug a regular phone into the wall jack and listen for a dial-tone.

Unplug the power cord for 10 seconds

Dear Harwoodian,
You can download the User Manual for you fax from this URL:

http://support-au.canon.com.au/EN/search?canonsearch=1&lang=EN&category=Faxes&series=Personal+BubbleJet+Faxes&model=FAX-B840&menu=Manual

Cheerup and Be Happy Always

The level of ink cartridge , can not be detected Solution :

1. resave the detection level Ink by entering the service mode
2. replace the ink detector