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Posted: Fri May 15, 2009 8:53pm

Post Subject: rev. counter query

have just purchased a narrowboat with a vetus 4 cyl. when the engine starts the rev. counter works o.k but after about an hours running the counter stops working and will only start again if the engine is stopped then restarted . the boat also has an adverc charging system fitted.


Posted: Sat May 16, 2009 8:27am

Post Subject: rev. counter query

Dear Robert, this could indicate a wiring problem, an alternator problem, or a revcounter problem. Check all the small terminals on the back of the alternator for tightness, cleanliness and the cable conductor being properly crimped into the terminal. Take care, one of the large terminals and possibly one of the small ones are connected directly to the battery so if you bridge these to any metal with a spanner you will get big sparks and may cause a fire. Check the terminals on the back of the revcounter. Next follow the main harness that runs from the instrument panel to the engine. You may well find as large connector block hidden away somewhere. With the revcounter not working but the engine running give this block a good twist and shake in case any terminals are loose or dirty, do not disconnect it. Next connect a voltmeter (set to 20V DC) across the engine battery bank and position it so you can see it whilst cruising. Keep a note of the voltage at any time. When the revcounter stops see if the voltage has dropped. If it has the alternator is probably faulty. If not it may still be one diode playing up in the alternator so set the meter to volts or better still Hertz (Hz) and connect this between negative on the back of the alternator and the connector that comes from the alternator. The reading should vary with speed but if it drops low as the revcounter stops registering it is either a wiring or alternator fault. Repeating at the alternator end of the cables will prove which. If all this seems OK then it is probably a revcounter fault. Notes:- 1. An alternator with one diode failed will normally still produce a charge so you can not use the fact its charging to assume it is OK. 2. Some Vetus engines have a relay and circuit breaker mounted on the back of the engine. IF there is a problem with the circuit breaker the engine electrics may lose power, but this should effect more than just the revcounter. I hope this helps and please let us all know what you find. Tony Brooks

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