A couple of questions I've been asked about the MD3B
. Anyone have any further information on the Volvo's?
1. When you install a Gauge, i.e., fuel level, water temp., oil pressure, tachometer, etc. etc. do you ALWAYS have to have that manufacturer's sending unit or are sending units universal innature?
Senders are matched to the Instrument Gauges by Resistance (American &
European), and by the number of Stations (Single Gauge, or Dual
Gauges) they will operate - hence any manufacturer’s appropriate
sender will operate any other manufacturer’s resistance matched gauge.
See the Charts
2. How do tachometer's sense the engine revolutions? I
have a Volvo-Penta MD3B in our boat. The Tach does not work. I found four (4) sending units on the engine. I can identify the water temp, and oil pressure but damned
if I can figure out what in the world the other two are for. I wonder if
one of them is for the Tach? Would a tach ever operate off of oil
pressure, similar to the way an oil pressure gauge works (sensing the pressure mechanically and then converting that to electrical going to the gauge)?
Tachometers work by counting the number of pulses generated by
a sensor (Alternator, Magnetic (Hall Effect) Pick-up, Mechanical
Pick-up), and converting this to Revolutions Per Minut