md11c rev counter

musarkie

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12 Apr 2010
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Hambleton, Lancashire
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I have a 1979 Volvo MD11C. The rev counter keeps failing then working again. Have cleaned the connection s on the sender unit and that didnt work initially, but then the diplay started working again.
Can anyone suggest whats the best way to fix it?
many thanks
 
Musarkie,

What do you mean by "the sender unit". I thought that rev counters take their input from the alternator (AC pulses before voltage/current rectified to DC).

So often a faulty rev counter can be traced to a faulty alternator or slipping belt.

Is the Volvo MD11C different ?
 
Musarkie,

What do you mean by "the sender unit". I thought that rev counters take their input from the alternator (AC pulses before voltage/current rectified to DC).

So often a faulty rev counter can be traced to a faulty alternator or slipping belt.

Is the Volvo MD11C different ?


Yes, it has an induction sender mounted above a timing gear. Usually fails due to poor
electrical contacts or sometime the sender fails which is big money if you can find one.
 
Musarkie,

What do you mean by "the sender unit". I thought that rev counters take their input from the alternator (AC pulses before voltage/current rectified to DC).

So often a faulty rev counter can be traced to a faulty alternator or slipping belt.

Is the Volvo MD11C different ?
This engine's different. MarineParts Europe list a tachometer sensor for €215. Ouch! Is there a fault in the cable giving you an intermittent connection?
 
Last edited:
The rev counter on my md11c is similarly caput. I have drifted into a practice of adjusting the revs by monitoring the engine temperature gauge and keeping it close to the 80 degree mark. If she is warming up in excess of that I cut her back. Engine temp is the bottom line really.
 
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