Engine hour meter wiring

aquaholic

aquaholic

Well-Known Member
Joined
17 Jul 2004
Messages
1,151
Location
London
Visit site
Have decided to fit a separate meter as the Volvo one has obviously given up the ghost long ago, any ideas where to wire it to, meter says it just needs + & -

Had a look at the wiring loom behind the Volvo control panel but didn't look to inviting to start fiddling with.

Volvo MD22L
 
Last edited:
aquaholic said:
Have decided to fit a separate meter as the Volvo one has obviously given up the ghost long ago, any ideas where to wire it to, meter says it just needs + & -

Had a look at the wiring loom behind the Volvo control panel but didn't look to inviting to start fiddling with.
Click to expand...

You could test with the meter for any piece of wiring that goes positive when you turn the ignition key on.
That way you don't necessarily have to dig deep. i.e. If the panel illumination is always on when the key is on then connecting to that will do.
 
aquaholic said:
Have decided to fit a separate meter as the Volvo one has obviously given up the ghost long ago, any ideas where to wire it to, meter says it just needs + & -

Had a look at the wiring loom behind the Volvo control panel but didn't look to inviting to start fiddling with.
Click to expand...

You can pick up the wiring in the Volvo panel if it suits you.

You don't say what engine but usually the blue/red wire from terminal 15 on the key switch is the switched positive ... you will see that it goes to the + terminal on the the rev counter.

The plain black wires are negative... the negative terminal on the rev counter may be a good place to connect.

I dont think you will find a suitable connection ( at least for the positive ) on the engine.
 
Talulah said:
You could test with the meter for any piece of wiring that goes positive when you turn the ignition key on.
That way you don't necessarily have to dig deep. i.e. If the panel illumination is always on when the key is on then connecting to that will do.
Click to expand...

You can pick up the wiring in the Volvo panel if it suits you.

You don't say what engine but usually the blue/red wire from terminal 15 on the key switch is the switched positive ... you will see that it goes to the + terminal on the the rev counter.

The plain black wires are negative... the negative terminal on the rev counter may be a good place to connect.

I dont think you will find a suitable connection ( at least for the positive ) on the engine.

Check the colour codes against the wiring diagram in the owners manual if there is one
 
Live from the ignition will run when the switch has been left on after you have pulled the strangler - unless, of course, you have one of those audible alarms connected to the ign and oil circuits, in which case it is unlikely to be left on. If you have splitter diodes (some old volvos had them on the back of the alternator) you could pick up a voltage from the B+ (alternator side).
It will only go positive when the engine is running.
 
I have just fitted one in the engine bay because the VP one in the rev counter has failed.
The boat wiring harness in the engine bay - without breaking into the VP multi way cable - includes a wire (orange on mine) from the alternator to the charge switching relay, with a spare female Lucar on it right by the alternator, I intend using that so it will only count when the engine is running even if the control panel switch has been left on.
Alternatively there is one that goes to the alternator via a dropping resistor to give it excitation voltage when the control panel switch is on. With engine not running that gives about 4V which I assume will rise to 12 when engine is running so would also serve. That circuit is shown in the MD2020D engine handbook (don't know what you have).
The alternator also has an earth stud on it. Very convenient.
I can't test yet - out of water.
 
Billjratt said:
Live from the ignition will run when the switch has been left on after you have pulled the strangler - unless, of course, you have one of those audible alarms connected to the ign and oil circuits, in which case it is unlikely to be left on. If you have splitter diodes (some old volvos had them on the back of the alternator) you could pick up a voltage from the B+ (alternator side).
It will only go positive when the engine is running.
Click to expand...

The standard Volvo hour meter built into the tachometer is simply connected to the supply (from the keyswitch) to the tacho. It runs while the key switch is on. If you forget to switch off after stopping the engine it continues to run ... tough ... remember to switch off!

BTW it is possible to replace the hour counter display in the tacho
www.dolcetto.org.uk/downloads/Replace Volvo Penta Hours LCD.pdf
 
Last edited:
aquaholic said:
Sorry guys it's a Volvo md22l
Click to expand...

In which case I can confirm that the positive wires in the panel are the red/blue wires.
They supply the tacho, the gauges, the instrument panel light switch and the "electronic module" from the key switch.

The negative wiring is the plain black wire that feeds the same items and the illumination bulbs

The wiring diagram does show a switched positive feed to the engine via the main wiring harness ( pin 3 on the multiway connector) but nothing on the engine is connected to it so probably not feasible to connect up in the engine bay.

The wiring diagram is in the owners manual available on line.
 
but is there any such connection at the engine or just at the ignition switch? Have tried the Fuel guage wires but it didnt work, was showing just 7.5v on the tester.
 
aquaholic said:
but is there any such connection at the engine or just at the ignition switch? Have tried the Fuel guage wires but it didnt work, was showing just 7.5v on the tester.
Click to expand...

The connection at the engine end is essentially a permanent positive coming off the starter motor.
(Big thick cable from battery to starter motor. (Most people have a switch in between.)
Relatively thin wire from starter motor connection then goes to engine panel providing a permanent positive at the engine panel on one side of the key. Other side of key goes live when key is in on position.
The fuel guage wires work by having + 12v on one side and then the negative side is connected to earth through a variable resister (the bit in the tank.)
Hence there is +12v on one side of the fuel guage when key turned on but if you measure the voltage across the guage itself the value will depend upon the level in the tank. The guage is just a voltmeter. As the tank is filled the resistance falls and the voltage increases. Did you measure your 7.5v between the + & - on the guage? If you had measured it across the +'ve and the main negative on the panel you would have had +12V.
There is a thin cable going back from the key switch to the solenoid on the starter marter.
This connection goes live when the key is turned to the start position.

Hence there is no real connection on the engine itself except as follows.
The stop solenoid.
When you press the stop button on the engine panel it provides power to the stop solenoid. The stop solenoid draws quite a lot of power and as a consequence a relay is often used. A smaller cable from the engine panel triggers the relay and then power goes to the stop solenoid. You can connect your hour meter to the power side of this relay. I don't know if this is the case for your engine though. It is the case for some Yanmars.

Apart from the engine panel most wires on a diesel engine are trying to connect to negative.
i.e. All those guages only have +12v at the panel, all the return wires are connecting to the negative through a variable resister mounted to the engine. For variable resister read temperature sensor, oil pressure sensor etc
 
Last edited:
Talulah said:
The fuel guage wires work by having + 12v on one side and then the negative side is connected to earth through a variable resister (the bit in the tank.)
Hence there is +12v on one side of the fuel guage when key turned on but if you measure the voltage across the guage itself the value will depend upon the level in the tank. The guage is just a voltmeter. As the tank is filled the resistance falls and the voltage increases. Did you measure your 7.5v between the + & - on the guage?
Click to expand...

That would explain why.... DOH!! So can I connect to the + on the fuel sender and the - to the battery???? or am I being dum?
Starting to feel out of my depth here......
 
aquaholic said:
That would explain why.... DOH!! So can I connect to the + on the fuel sender and the - to the battery???? or am I being dum?
Starting to feel out of my depth here......
Click to expand...

Yes. That's correct.
Incidentally you should find that the positive on the guage is chained to the positives on the other guages.
 
Last edited:
davidjackson said:
Have you fitted a second, stand-alone hour meter rather than attempt to replace the Volvo jobbie? If so, where have you put the new meter. Any chance of a picture?

Another job for the "to do" list.
Click to expand...

Can you see the new meter next to VHF? The Volvo jobbie works once every two years and I really couldn't be bother fixing it!
 
aquaholic said:
but is there any such connection at the engine or just at the ignition switch? Have tried the Fuel guage wires but it didnt work, was showing just 7.5v on the tester.
Click to expand...

I have gone to the trouble of down loading the manual for your engine,

I have studied the wiring diagram and I have told you where to connect the timer. I have told you the colour of the wires to connect it to.

I have told you that the wiring diagram shows no convenient connection in the engine bay.

Read my posts ... look at the wiring diagram in the owners manual for yourself

Do as I suggest and it will work!
 
You must log in or register to reply here.

Share this page

Top