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Discuss 12V DC Relay Issues (Diesel Engine) in the Advice for Professional Canadian Electricians area at ElectriciansForums.net

Hello all. I am having an issue with a 12V DC Relay I am trying to install to run a kill switch on a John Deere Diesel engine that runs a high pressure water pump. I have the relay wired in such that it will send power to the ignition when an electrical signal comes from a water sensor in the pump (dry running protection). The issue I have is that whenever it is hooked up all I get is chatter from the relay. I have tested my wiring by connecting the "switch" wire to battery and everything works as it should. I read somewhere that if the switch voltage is less than the feed that it can cause chatter. The fees voltage is 12.56 and the switch voltage is 12.22. Could this be the reason and how should I go about fixing it? Thanks
 

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telectrix

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12.22V should be enough to energise the relay. is it dropping under load?
 

Spoon

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So the signal from the water sensor is ok then and this is not causing the relay to chatter?
 

telectrix

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relay needs cheesecake.
 
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  • #5
The sensor is sending a constant 12.22 volts. And the chatter happens whenever the sensor wire is sending power, engine running or not. When it's chattering there is no power to the box with the ignition so it can't be running anyway.
 

Spoon

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I presume you don't have a variable power supply. To feed 12.22v from this to the relay and still see if you get chatter...
 

Lucien Nunes

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A 12V relay will usually pull in around 8-9V on the coil, and will hold in down to about 6V. Anywhere between 9 and 18V should be OK, it is not critical. There is no relationship between the coil voltage and the contact switching voltage. Probably, the sensor output is not giving a steady voltage, or there is a bad connection somewhere, or the relay is not actually a 12V relay.
 
  • Thread Starter Thread Starter
  • #10
A 12V relay will usually pull in around 8-9V on the coil, and will hold in down to about 6V. Anywhere between 9 and 18V should be OK, it is not critical. There is no relationship between the coil voltage and the contact switching voltage. Probably, the sensor output is not giving a steady voltage, or there is a bad connection somewhere, or the relay is not actually a 12V relay.
Okay thanks. I will check with the sensor manufacturers and see if it is constant or not to double check. If it isn't, is there anything that can be done or a different style relay to use?
 

Lucien Nunes

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What type of output does it have - contact closure, open collector? Is it designed to operate a relay or just trigger an electronic input of a system controller?
 
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  • #13
It is grounded to a point on the frame of the unit. When it senses the water it closes a circuit with the power feed to send power down the switch wire. I think it is designed to be used in a system controller but the dealer said people have used it to operate a relay.
 

ruston

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Advent Win
Is the battery ground and the frame ground connected to give the relay a good connection?
 

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