Originally Posted by Morgan320i
Got caught in a storm couple days ago had to motor out I have a Volvo md2b
oil pressure, turned off, cleaned oil screen
checked oil, no change,
No increase in engine
temp stayed below 150,
I’m assuming my gauge is bad or my sending unit as if I really had no oil pressure I’d have blown my motor after 3 days of sailing and or motoring home,
Starts and runs like a top no weird noises
Motor is from the 70s, gauge looks original, line is old ,
Welcome aboard CF, Morgan320.
Is you existing gauge electrical
, you can test the sender, wiring
and gauge and simply replace the faulty item.
The sender simply changes it's resistance as the oil pressure rises and falls. Use a DMM on the ohms setting and measure the resistance in the sender at zero oil pressure (i.e. engine OFF), measure it again at idle and at normal running rpm
. If your sender is European, it will rise in resistance as oil pressure rises from a few ohms to a few hundred ohms. If it is North America, it will do the opposite.
If the sender is OK, make the same measurements on the sensing terminal on the back of the gauge (with the sender reconnected). It should be the same if the wiring
is OK. Also measure you have 12V across the +ve and -ve terminals on the gauge. If gauge does not operate and has 12V and the sense wire tracks the sender, the gauge is faulty.
A quick and dirty test is even more simple. Making sure the instrument panel is powered and the engine is OFF. The gauge should read 0. Now take the wire off the sender. If European, the gauge should go to full scale deflection. If North American, you will need to touch the wire to the engine ground to get full scale deflection.