Save-A-Boat - The Forum for Plastic Classic Rebuilds!

The Oil pressure alarm fails to register on my Yanmar 1gm10. I want to figure out if it is the sending unit. How do these work?

There is one wire coming out of it. I disconnected it and touched it to 12 volts and also to ground. Nothing. I tried the same with the temperature sensor which works and also got nothing. How do I test to see if the sending unit is bad? Is it worth taking out and cleaning if it is bad or should I just replace?

Thanks in advance for any help
Brock

I'm sure if it were me that I'd simply order a new one and replace it.

I had to replace mine when I broke it during engine removal a couple years ago and I think the new on cost about 6 bucks. I'd just get the new one.

I guess I could probably spring for the six bucks. I was really wondering why I couldn't get the buzzer to sound by connecting the wire of either sensor to 12 volts or ground. It just didn't make sense to me.

thanks for the info
Brock

Brock,

Nigel Caulder has a whole section on testing your instruments which I've paraphrased below. I'm installing all new instruments now so I'm going through this myself.

Test for 12v from the guage + to a good ground. If no volts, the ignition switch circuit is faulty.

To test the alarm or light, disconnect the wire from the sending unit and short it to a good ground. The alarm should go on. If not, do the same test from the second terminal on the alarm to a good ground. If still no response, the alarm is faulty. If you do get a response from this, the wire to the sending unit is faulty.

To test the sending unit, switch off the ignition, disconnect the wires and test with an ohm meter from the sending unit to a good ground (usually the threaded insert on the sender). For the temp. you should have higher ohms when cool or lower ohms when hot. For the oil pressure, Caulder says the the senders vary from 0 ohms at no pressure to 200 ohms at high pressure. You are looking for a clear difference in ohms (ohms) with a change in temp or pressure.

What is not clear to me is how you get a change in pressure with the engine off, but maybe its cheaper to spend the $6 and replace. :)

If you do get a new alarm, be prepared for a shock. I replaced mine after a hurricane left the boat awash and as I recall it was $100 or more. I think you are right, however, to insist that this element of you mechanical system work properly, no matter the cost.
Chris Miller
Seafarer 31 yawl
Lloyd, Florida