Fitting a Tachograph
Unless you are only taking
your bus with less than 8 passengers to historic vehicle rallies or for
maintenance or repair you need a tachograph. This matter has been researched
extensively by the owners of historic vehicles and there is a good summary of
the legal position on the Routemaster
Association’s website and a detailed account of the Drivers'
Hours and Tachograph Rules in the UK and Europe.
This is how I fitted a
tachograph to RM471 on
I had no working speedometer
and there was a tachograph sender fitted where the speedometer generator should
be situated. I decided not to repair or replace the speedometer generator and
speedometer but fit a tachograph instead. Some owners have had a tachographs
fitted in addition to the speedometer using pulses generated by the nearside
gearbox sender necessary for fully automatic operation of the self changing
gearbox but there are problems with this method. Anyway my bus does not have a
nearside gearbox sender!
I fitted a new tachograph
sender unit to a tachograph adapter on the offside of the gearbox where the
speedometer sender is usually situated.
I routed the cable from the
sender in the conduits (when I could) or cable clipped it to the conduits
provided for the speedometer and gearbox cabling (when I couldn’t) all the way
to the cab.
I bought a “scrap”
tachograph head unit from a local commercial vehicle scrap yard and mounted
this in the cab in the space previously occupied by the cab light.
The cable from the sender
plugs into the back of the tachograph. Another plug supplies +24V, two –24V
connections and a supply which is live when the ignition is on and another
which is live when the side lights are on. It is easy to pick up these
connections from the switch panel above and to the left of the driving position
which includes the “coat-hanger” starter.
The new sender cost £67, the
wiring cable assemblies with connecting pugs cost £80. I installed all the
units and wiring myself. About two hours work.
Testing the tachograph head,
calibrating it on a rolling road and sealing the sender and head cost £45. This
needs to be done at a tachograph
calibration centre.
The whole cost, including
VAT (but excluding my labour) was just under £350. Tachograph discs cost about
£4 for a hundred.
Wiring details
From sender unit to
tachograph head
1-Black, 2-Brown, 3-Blue,
4-White
Power to tachograph head
1 +ve 24V permanent, 2 +ve 24V
sidelights, 3 +ve ignition, 5 –ve, 6 –ve.
Part numbers
I needed a 4 pin “18” sender
unit to match my tachograph head. The parts I needed to buy were as follows
MA204120-4 sender unit
ZT60755792 wiring loom
ZT 60795575 wiring loom
Advantages
Being legal – Having an
accurate speedometer – Having an accurate odometer (in kilometres) – having a
clock in the cab
Disadvantages
Isn’t an original feature –
Need to change the disc every 24 hours and write in drivers name, start and
finish location and odometer reading every day - keep the discs for inspection
in the vehicle for one week and somewhere else for 3 months after that – the
clock needs to be reset whenever the battery power is disconnected.