Wiring gurus - electric water pump warning light help
#1
Wiring gurus - electric water pump warning light help
Hey guys,
I have a '97 LT1 SS with a Meziere electric water pump. I am trying to wire an LED that will stay lit whenever current is flowing through the ground wire for the pump. That is, I want to run an LED in series with the water pump, with the ground wire for the pump serving as the positive current for the LED.
This arrangement seems to provide the best indicator as to whether the pump is working. I have seen many circuit designs on the internet that purport to include water pump warning lights, but the warning lights in those circuits actually only ensure that the relay on the positive side of the pump is working. The wire connection going into my pump is a bit fickle. Testing current on the ground side of the pump will rule out a bad relay, a bad fuse, a bad wire going into the pump, and any electrical problem within the pump. Only a mechnical failure that does not impede current will go undetected.
This circuit at least addresses the ground side of the water pump, but it tests for a ground failure instead of normal operating current:
http://ls1tech.com/forums/lt1-lt4-mo...waterpump.html
I don't see how a ground failure is a real threat. I want a light to illuminate when there is current flowing through the ground wire for the water pump, not when the wire I have securely bolted to the frame as a ground mysteriously comes loose.
So far, I've tried many different ways to do this, without success. I'm worried there is no way to do this. An LED only flows about 30 miliamps of current, so the 20 amp water pump won't run with all of the current flowing through the LED. I have tried a relay with the water pump ground as the trigger; the relay clicks on, but the water pump doesn't turn on because (I assume) the trigger side of the relay does not flow enough current to run the pump. I have tried an illuminated rocker switch, but the light won't turn on either when the pump is running or when there is no power coming through the pump. I've messed with a 12-volt diode spliced into the ground wire and then to the LED, and that doesn't work either.
I imagine the solution, if there is one, involves diodes, transistors, resistors, etc. - stuff I really don't understand. If anybody has a clue how to wire this, or can suggest an alternative circuit design that will accomplish the same thing (test for a charge coming out of the water pump), please help! Maybe there is a relay, or a way to wire a relay, that will solve this problem.
I have a '97 LT1 SS with a Meziere electric water pump. I am trying to wire an LED that will stay lit whenever current is flowing through the ground wire for the pump. That is, I want to run an LED in series with the water pump, with the ground wire for the pump serving as the positive current for the LED.
This arrangement seems to provide the best indicator as to whether the pump is working. I have seen many circuit designs on the internet that purport to include water pump warning lights, but the warning lights in those circuits actually only ensure that the relay on the positive side of the pump is working. The wire connection going into my pump is a bit fickle. Testing current on the ground side of the pump will rule out a bad relay, a bad fuse, a bad wire going into the pump, and any electrical problem within the pump. Only a mechnical failure that does not impede current will go undetected.
This circuit at least addresses the ground side of the water pump, but it tests for a ground failure instead of normal operating current:
http://ls1tech.com/forums/lt1-lt4-mo...waterpump.html
I don't see how a ground failure is a real threat. I want a light to illuminate when there is current flowing through the ground wire for the water pump, not when the wire I have securely bolted to the frame as a ground mysteriously comes loose.
So far, I've tried many different ways to do this, without success. I'm worried there is no way to do this. An LED only flows about 30 miliamps of current, so the 20 amp water pump won't run with all of the current flowing through the LED. I have tried a relay with the water pump ground as the trigger; the relay clicks on, but the water pump doesn't turn on because (I assume) the trigger side of the relay does not flow enough current to run the pump. I have tried an illuminated rocker switch, but the light won't turn on either when the pump is running or when there is no power coming through the pump. I've messed with a 12-volt diode spliced into the ground wire and then to the LED, and that doesn't work either.
I imagine the solution, if there is one, involves diodes, transistors, resistors, etc. - stuff I really don't understand. If anybody has a clue how to wire this, or can suggest an alternative circuit design that will accomplish the same thing (test for a charge coming out of the water pump), please help! Maybe there is a relay, or a way to wire a relay, that will solve this problem.
#2
Re: Wiring gurus - electric water pump warning light help
The relay should work, that's what they are for.
Was the one you used rated high enough?
Pump to the relay (86), relay (85) to ground.
12v to the relay's switched (87), relay's switched (30) to resistor, led, and then to ground.
When the 12v is going through the ground it will cause the relay to activate and make the LED light up. If the fuse blows or for whatever reason the 12v stops flowing on the ground wire the LED will shut off because the relay will not close the switch.
All you need to do to make the LED work on a 12v current is wire in a resistor. I have a chart somewhere that shows what resistor to use to cut voltage down for an led. I will see if I can find it.
You can do the opposite with a 5 pin relay. Wire the LED's power from the ignition switch to (87A) As long as the 12v flows it will keep the switch open, if the 12v goes away it will close the switch causing the LED come on.
A second idea could be to splice the ground, similarly to what you did with the diode, but run the ground as normal and "Y" off with a wire that goes through a resistor and the LED then to a ground somewhere else. Also, you connected the Diode with the correct polarity right?
Even if you spiced off and then ran a resistor, led, then diode, then back to the same wire or ground it should illuminate. You just have to make sure the polarity of the LED and Diode are both right. The resistor won't have a polarity.
Hope this helps.
Was the one you used rated high enough?
Pump to the relay (86), relay (85) to ground.
12v to the relay's switched (87), relay's switched (30) to resistor, led, and then to ground.
When the 12v is going through the ground it will cause the relay to activate and make the LED light up. If the fuse blows or for whatever reason the 12v stops flowing on the ground wire the LED will shut off because the relay will not close the switch.
All you need to do to make the LED work on a 12v current is wire in a resistor. I have a chart somewhere that shows what resistor to use to cut voltage down for an led. I will see if I can find it.
You can do the opposite with a 5 pin relay. Wire the LED's power from the ignition switch to (87A) As long as the 12v flows it will keep the switch open, if the 12v goes away it will close the switch causing the LED come on.
A second idea could be to splice the ground, similarly to what you did with the diode, but run the ground as normal and "Y" off with a wire that goes through a resistor and the LED then to a ground somewhere else. Also, you connected the Diode with the correct polarity right?
Even if you spiced off and then ran a resistor, led, then diode, then back to the same wire or ground it should illuminate. You just have to make sure the polarity of the LED and Diode are both right. The resistor won't have a polarity.
Hope this helps.
Last edited by calaban; 09-28-2011 at 04:06 PM.
#3
Re: Wiring gurus - electric water pump warning light help
On second thought you may not need the second Diode to begin with as the LED will only allow current to flow one way since it is a diode in itself.
#4
#6
Re: Wiring gurus - electric water pump warning light help
If enough people were interested, I could design a fairly simple electronic circuit that directly monitors actual pump current draw and indicates if it's out of 'range'.
#7
Re: Wiring gurus - electric water pump warning light help
Thanks, guys.
Calabran, the first two ideas you raise have not worked for me. The relay I have is rated at 25 amps, but I assume that is for the switched side. The pump only draws about 7 amps during normal operation. The relay triggers when I run the pump wires on the trigger side, but the pump does not work. I assume the relay doesn't flow enough current on the trigger side to accommodate the pump.
I am on to a diode that may do the trick: http://www.jameco.com/webapp/wcs/sto...0001_179485_-1
And I'm looking for a relay that can accommodate flow of 10+ amps on the trigger side (86 & 85).
Calabran, the first two ideas you raise have not worked for me. The relay I have is rated at 25 amps, but I assume that is for the switched side. The pump only draws about 7 amps during normal operation. The relay triggers when I run the pump wires on the trigger side, but the pump does not work. I assume the relay doesn't flow enough current on the trigger side to accommodate the pump.
I am on to a diode that may do the trick: http://www.jameco.com/webapp/wcs/sto...0001_179485_-1
And I'm looking for a relay that can accommodate flow of 10+ amps on the trigger side (86 & 85).
#9
Re: Wiring gurus - electric water pump warning light help
And in that thread you linked too, the pencil/pen schematic (with one change to make the 2nd relay get an ign hot source not a battery hot source) will work fine to sense the actual voltage flow to the pump (not a ground failure).
Without getting into a current sensing circuit (which would require some of the transistors/comparators) that's the simplest/best schematic I've seen.
Without getting into a current sensing circuit (which would require some of the transistors/comparators) that's the simplest/best schematic I've seen.
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