Inexpensive engine temperature alarm

[randyo]

Im looking to build an inexpensive temperature alarm to warn me of my boat overheating.<br /><br />I've searched and found the following posted by Don and others:<br /><br />

All you need is a Normally open temperature switch from your local auto parts store with around a 200° to 210° closing of the switch. Then get a 12V buzzer from radio shack and some wire and you have an alarm.

My question is the following:<br />Does this temperature switch actually measure the water temperature or can it be piggy-backed onto the wires leading to my existing temperature gauge to sound an alarm?<br /><br />Im looking for an "easy" installation - wires and batteries I can handle. Putting new holes in my engine for temperature sensors is *way* out of my league. BTW, this is for a 175 Glastron with V6 Volvo engine.

 

[MainstreetUSA1]

Re: Inexpensive engine temperature alarm

You'll need to plumb it in with a tee so you can have your temperature sending unit and temperature alarm switch unit both in contact with the engine cooling water at the T-stat housing.<br /><br />Here's an example with a oil pressure alarm too:<br />

 

[searay3]

Re: Inexpensive engine temperature alarm

Not sure how much room you have, but you could put a short galv pipe to create a 'T' fitting where the original temp sensor screws into the block, and wire it as you describe. The position of the switch is critical to read true engine temp. That was figured out by the engineers. It won't be pretty, but it will give you an audible alarm. The only issue I can think of is it might not be dead on temp wise since it is not in the waters direct stream but an inch or two away.

 

[bruceb58]

Re: Inexpensive engine temperature alarm

Almost all the inexpensive alarms you find out their are what mainstreet described in his drawing.<br /><br />Most boats have guages for oil pressure and water temp so the sending units are not switched but variable resistors. The guages put a voltage to the senders and basically measure the resistance.<br /><br />To do what you want to do is to buy or make a unit that also measures these sending units in parallel with the guages and have a voltage comparator that can turn an indicator on and off.<br /><br />I was actually thinking of designing a little circuit to do that. Not sure if that is something you are up to or not.

 

[Bt Doctur]

Re: Inexpensive engine temperature alarm

Have someone SIT on the risere/elbow.<br />cheap/very effective/multiple usage