Re: The 175 merc AGAIN! (alarm question)
There are sending units to monitor oil level,oil delivery, and engine overheating.<br />First step is to determine which alarm is sounding and ,of course, why.<br /><br />It is more than likely, a defective sender, or a short in the wire harness. I would look at the sender secondly. Remove the one wire comming from it, and check for any corrosion at the tip , where the wire connects. It should be shiny clean. If there is any corrosion it will make a path to ground, and act like a resistor.<br />Speaking of that, the sending unit is a THERMistor . This is a resistor that changes it's value with temperature. They are used in ovens, temp sending units in auto,marine and aircraft engines, coffee makers ect..As the water temperature increases, the resistance increases,to a point where there is a direct path to ground. A standard ohmeter, hooked-up to a thermistor will act like a temp gauge ior thermometer (unscaled, of course).An oil sender senses changes it's resistance in porportion to the oil around it, the pressure it is subjected to, (as in an oil pressure gauge),or the conductivity of the fluid around it.<br /><br />On the oil sender, there are several types. But most can be checked with an ohmeter, and a shop manual showing the normal values the reading should fall inside of.<br />They should read open circuit with the wire disconnected in most cases, but I am admittedly, unfamiliar with your particular engine, and which alarm is falsing.<br /><br />Before running this engine anymore, make doudlty-dagone sure that the alarm isn't trying to warn you of an oiling or cooling failure.<br />Replace all the senders if you must.
