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-   -   Temp Sending Unit on Heat Riser - how to test? (http://www.sailnet.com/forums/gear-maintenance/54554-temp-sending-unit-heat-riser-how-test.html)

preservedkillick 05-21-2009 07:50 PM

Temp Sending Unit on Heat Riser - how to test?
 
I've got a temperature sending plug on the heat rider coming off the back of my Vetus engine with no wire connected to it. I'm trying to figure out which wire connects to the spade connector on the sending unit, not (yet) if the sending unit works. The wire according to the wiring schematics that should connect, is not, but is connected to a plug on the engine pan (the very bottom)?

What I'd like to do is see if I can trigger the high temp alarm using that wire, but I'm not quite understanding how the sending unit works. With just a single wire, I'm assuming the sending unit closes a circuit by grounding the wire lead to the engine block?? If I take the wire and touch it to ground, shouldn't the alarm activate??

Am I close?

-Preserved.

tommays 05-21-2009 08:08 PM

There is generally a sender that that changes Resistance to control the gauge and if you touch the CORRECT wire to the block the gauge should move

And a separate unit with a switch that would run the alarm at the temp that is to hot

lshick 05-22-2009 01:06 AM

There are two types of senders: those that drive a gauge, and those that drive an alarm. tommays is correct about the behavior of a sender that drives a gauge. In many cases, a sender that drives an alarm is mounted on the ground side of the alarm circuit; in case of an overheating situation, the switch inside the sender closes to complete the circuit to ground.

I have tested the alarm on my boat by touching the wire to ground, as you suggested.

preservedkillick 05-22-2009 07:59 PM

Thanks guys, it's a single wire. I'll test by grounding.


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