Volvo penta rev counter not reading and engine hour read out fading in and out?

[sthurley]

Do I need a new rev counter? Its connected to a md2020, when power is switched on the needle flicks slightly.

 

[nigelmercier]

First step is to check the connections; could also be corrosion inside. I've taken a few of these apart, so happy to take a look.

 

[sthurley]

Connection look good. Does it come apart easily? I have nothing to loose so may as well have ago, any tips?

 

[nigelmercier]

Ideally use long sockets on the two brass double-ended screws. Once you have done that, the back unscrews about 1/4 turn and comes out of the casing. The clear cover should just pull out, I use a suction puller. The needle comes off by pulling the hub, try fingernails first, or a couple of cocktail sticks can be used as levers under the hub.

The points that corrode are the pins that connect the PCB to the FastOn connectors on the case, they are a bugger to clean up. If you have corrosion on the PCB also, unsolder the motor then try an ultrasonic bath.

If you give up, please don't chuck it away, I want one to play with.

 

[sthurley]

Thanks for this, I will take it apart and have a nosey - ultrsonic bath out of my league though!! I will let you know what the outcome is - may be a while though.

 

[nigelmercier]

... ultrsonic bath out of my league though!.

That's why I offered to take a look for you, I've got a lot of gear for dealing with PCBs, and it so happens that I want a unit to check something on another faulty unit. My offer is still open, only cost to you is the postage. PM me if interested.

 

[sthurley]

Took the unit apart last night, gave all the connections a bit of a rub. Will reconnect the unit some time this week to see if any change after thatif no change I will send to you. Will pm you for address.

 

[sthurley]

Well drama over. Having read lots on the web to decipher the alternator connections I discovered that the previous owner or a mechanic had put the vdo sender wire (blank and grey) on the battery negative post instead of the w post! Rev counter working a treat. The LCD display however not showing. Rather than replacing it I am just going to put in a counter and tuck it out of the way, after all how often do we look at them! That way the current counter will keep recording and may display on occasion when the mood takes it. I have blown the small red capless bulb but looks like a standard item out of an autospares shop.

 

[nigelmercier]

... The LCD display however not showing...

This is a common problem, drying out the unit can help, but it needs to have any salt washed out first (hence my offer to use an ultrasonic bath).

I have an instruction sheet to replace it if required, see the Downloads section from the link in my signature. If you do, please don't throw the old LCD away, I want one to play with.