Rev counter any ideas??

[MJWB]

Just lately some weird behaviour from the rev counter for the VP 2002 in my boat. Engine starts pretty much okay, partic today. But lately when she fires and the revs climb quickly to throttle start setting, the rev counter misbehaves. Rev counter shoots up to the revs then after a second at most it drops to zero and generally won't move. Occassionally it does settle on the proper rev setting after a bit, but generally not. Today I gave it a run and it did as described at start. Then after a few minutes it would climb a bit as revs increased but was reading 1000 when the donk was turning at about 2200 by my best guess. I've given the back a good spray in case that might help. God knows that's my limit. Any ideas or advice please would be most welcome indeed. Please folks give me a steer

 

[Stingo]

Check all the wiring connections on your alternator - one of which actually controls the rev counter

 

[VicS]

It's the grey wire which is the signal from the alternator.

Also check the multi pln connectors in the wiring and the power supply to the tacho, Blue/red is the positive and black the negative

 

[Momac]

I had the signal wire break the alternator due to vibration/fatigue. The wire had a spade terminal . I changed that to a ring terminal on the wire - which seems to be considered the better option.

 

[Martin_J]

As others have said, it's really a case of checking for integrity of the wires.... unless you have access to a small oscilloscope.

Quick video below (on my OneDrive) showing that the signal on the alternator wire shows much clearer on that than on a multimeter..

https://1drv.ms/ VP tacho signal

 

[peteK]

I have had this problem a couple of times in the last 10 years and found that cleaning the brushes/commutator on the alternater cured the problem.

 

[Refueler]

I have had this problem a couple of times in the last 10 years and found that cleaning the brushes/commutator on the alternater cured the problem.

Surely such need would have triggered audible no charge alarm ?? ..... Just thinking ... 'Brushes ? on an alternator ??

 

[VicS]

Surely such need would have triggered audible no charge alarm ?? ..... Just thinking ... 'Brushes ? on an alternator ??

What are you thinking about alternator brushes ?

Part of the regulator assembly in the VP 2002 alternator .... VP's price €337 !

 

[peteK]

Its actually on a Perkins m20 Lucas A127 with isolated return

 

[Refueler]

What are you thinking about alternator brushes ?

Part of the regulator assembly in the VP 2002 alternator .... VP's price €337 !

Never had alternator apart .... older Dynamo / Dynastarts - yes. Having moved from brushed motors / generators etc. to Brushless - and the alternators on my items having no visible exterior point of brushes .... 2 + 2 =5

 

[MJWB]

I have had this problem a couple of times in the last 10 years and found that cleaning the brushes/commutator on the alternater cured the problem.

How do you do that please?

 

[MJWB]

Many thanks all for your advice and replies.

 

[Yara]

Just a quick question on Volvo generic 2000 series rev counters. I presume that the connection G is for negative (Ground) terminal? There are also + and - connections, but it looks like they are for the light.

 

[Dantp]

In some of this series of engines (ours does) there is a tacho sensor on the engine rather than the signal coming from the alternator.
This is on the front just above the oil filler cap with I think 2 wires going to it.
Check the word and connection to this (pull them off give them a spray and a clean). Sometimes cables fail (or get a bit sketchy )at the point of the spade connector.

 

[Yara]

The wiring on my VP2001 control panel has been changed, and the rev counter is missing. I acquired a second-hand panel with rev counter and I want to fit the rev conter. Unfortunately the Volvo-Penta wiring diagram in the manual is not very clear- the G connection from the rev counter shows goes to a terminal not connected to anything. I am 99% sure it is meant to be ground-i.e. negative battery terminal, but could someone please confirm?