Oil pressure gauge

[marcjagman]

Can anyone tell me how to wire an oil pressure gauge up to a RV8 please? i have found an old one and want to check everything is okay. Is it simply a case of 1 wire +ve and 1 wire to the sender unit?

[kiwicar]

That sounds about right to me,
Best regards
Mike

[ramon alban]

Hello Marc, this is the wiring diagram for the late SD1 V8 gauges annd senders.

[marcjagman]

Thanks chaps

[DaveEFI]

Can anyone tell me how to wire an oil pressure gauge up to a RV8 please? i have found an old one and want to check everything is okay. Is it simply a case of 1 wire +ve and 1 wire to the sender unit?

[Denis247]

The oil pressure gauge reading will vary with the 12v level, why isn't it connected to the stabilised 8v as per the fuel and temperature gauges ?

[kiwicar]

Hi
Because it is only active (ie not on the end stop) when the engine is running, ie when the altinator is holding the +ve rail at a steady 12.9 to 13.5v (depending on altinator).
Best regards
Mike

[DaveEFI]

The oil pressure gauge reading will vary with the 12v level, why isn't it connected to the stabilised 8v as per the fuel and temperature gauges ?

It's a different type of meter movement - moving coil - which has a voltage compensation coil built in, unlike the slow reacting (and cheaper) hot wire ones used for fuel and temperature.

[Denis247]

The oil pressure gauge reading will vary with the 12v level, why isn't it connected to the stabilised 8v as per the fuel and temperature gauges ?

It's a different type of meter movement - moving coil - which has a voltage compensation coil built in, unlike the slow reacting (and cheaper) hot wire ones used for fuel and temperature.

But the temperature gauge IS fed from the stabilsed supply!, and the point about only being powered when the engine is running, well that goes for the other two gauges as well, or rather when the ign switch is on anyway. And my 'nominal' 12v , with battery in the boot, varies by quite a bit more than quoted, especially in the winter, that's why a regulated supply is used to power the gauges.
Anyone checked to see that the circuit diagram hasn't mistaken the connections ? (Can't check myself as I have a mechanical oil pressure gauge.)

[kiwicar]

"and the point about only being powered when the engine is running, "
actually the point I was making is you only have pressure when the engine is running, so zero pressure is zero pressure regardless of what full scale referance is.
Best regards
Mike

[DaveEFI]

If you look at the circuit diagram you'll see the oil gauge has three connections - +12v, ground and sensor. Inside the moving coil meter is a voltage compensating coil.

The other meters have only two wires connecting them, and are hot wire types, which need a regulated voltage, provided by an external unit. Hot wire gauges are much cheaper to make. They also react to change much more slowly than a moving coil type - ideal for fuel and temperature, but not for oil pressure.

[Denis247]

If you look at the circuit diagram you'll see the oil gauge has three connections - +12v, ground and sensor. Inside the moving coil meter is a voltage compensating coil.

The other meters have only two wires connecting them, and are hot wire types, which need a regulated voltage, provided by an external unit. Hot wire gauges are much cheaper to make. They also react to change much more slowly than a moving coil type - ideal for fuel and temperature, but not for oil pressure.

Appreciate the explanation, thanks.
I understand the moving coil-type meter being used to give an faster response time, but I didn't realise it had it's own integral regulator, just thought it might have been an error in the diagram.
Never used an electrical oil pressure gauge myself, my car, being 1976, has all original gauges including the mechanical oil pressure.
You live and learn, thanks again.

[marcjagman]

AND it's an aftermarket gauge that I have