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Temp and Pressure Senders NC or NO circuits

ehlien

ehlien

Regular Contributor
"Help
Does anybody know if te

"Help
Does anybody know if temp senders, pressure senders and drive float valve/senders are normally open or closed switch circuits?"
 
"Senders for gages or for alar

"Senders for gages or for alarms? The only thing NC or NO could refer to is senders that are switches for alarm or warning light circuits. Senders that drive gages are resistive circuits to ground either internally or externally grounded, i.e. one or two contacts on the sender. The hot goes to the gage and depending on temperature/pressure etc. a better or worse connection to ground (the engine block) is made and that drives the gage. An alarm is normally a NO circuit unless the circuit is changed with a relay.

Warning! I have no particular knowlege of Mercruiser gages, i am just explaining how gages and senders work in general.

Ted"
 
"The gauges are driven by anal

"The gauges are driven by analog (variable resistance) sensors which are usually single wire with the other path of the circuit being the case to ground..

The sensors for the alarms are switches, and for sure the oil pressure one is N.O., i.e. Normally Open and closes when the oil pressure rises to an acceptable value... at least on my 5.7MIE."
 
"Thanks Just to carify ..N.O.

"Thanks Just to carify ..N.O. means the switch circuit is open/contacts not connected /not flowing , N.C. means the circuit is closed/contacts touching/ flowing current or am I backwards?"
 
Robert then you must have a re

Robert then you must have a relay in your circuit. If you didn't then when your oil pressure switch closed after your engine comes up to pressure it would send ground to the buzzer?
 
Oil pressure switch also contr

Oil pressure switch also controls the electric fuel pump per regs. I suspect the reason its a N.O. contact is to prevent operation of the fuel pump if someone disconnects the oil pressure switch to silence an alarm.
 
"there are both versions of th

"there are both versions of the single throw oil pressure switch...which one you use is driven by the application. (there is also a SPDT version, too.) The N.O. versions are typical in the audio warning loop and are also used as an input to the ECU, where it controls the fuel pump. The N.C. versions are typically used for 'autonomous' control of the pump. This route provides the safety shutdown in case of 1) loss of oil pressure or 2) physical failure of the switch."
 
"Sorry - switched the C and th

"Sorry - switched the C and the O - here's the corrected version of my previous post:

there are both versions of the single throw oil pressure switch...which one you use is driven by the application. (there is also a SPDT version, too.) The N.C. versions are typical in the audio warning loop and are also used as an input to the ECU, where it controls the fuel pump. The N.O. versions are typically used for 'autonomous' control of the pump. This route provides the safety shutdown in case of 1) loss of oil pressure or 2) physical failure of the switch."
 
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