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Not a waxer
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12,092 Posts
You can simply wire a lamp in parallel with the power feed to the pump's motor but that will only tell you that it is getting power, not if it is actually pumping coolant, such as if the pump fails but the motor still runs.

Jeff
 

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Certified Mad Scientist
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2,151 Posts
You could run a normally closed relay for the light circuit that cuts power to the light whenever the power to the pump motor fails. The power for the light would need to come from a switched power circuit to keep the light from being on all the time with the ignition off.

I would do it differently. When I installed an auxiliary oil cooler and fan on my SRT8 Jeep, I used an SPCO (single pole, center off) switch to route power to the fan relay either directly through the switch (ON), or through the thermostat (AUTO), with a green LED powered by the relay so that the light would be on whenever the fan was on. The LED was initially too bright, so I added a resistor in the light circuit to dim it to a reasonable level. As the oil temp climbs, I can monitor the light to see when the fan comes on, I can leave it off in cold weather, or manually turn it on when I know the oil will be getting hot quickly (pulling a trailer or hammering on it).

Here's the switch:



Anyway, you might want to consider running a light to show that you have power to the pump so you can see that it's on. Your temperature guage should let you know if you have a cooling system problem, and the pump failure light would only tell you that you've lost power to the pump. If the pump fails, it might not overload the pump circuit and blow the fuse, and the pump fail light wouldn't come on. In that case, your only indication would be a temp increase. If you have a "pump on" light and you see the temp go up, and the pump power light is off, you'll know the pump power circuit has failed. If the light is on, it still might be a failed pump, but is more likely another problem.

Hope that helps!

Eric
 

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Official OLD GUY
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3,877 Posts
Water Flow Sensor

You might want to look into a Hi-Temp water flow sensor. You might need to build a by-pass to flow water thru it ( direct flow would create a "restriction" in the path, but it's probably the only way you'll get an absolute indication that you have water flow. Tying lights to the pump circuit will only tell you that the pump has failed, your temp gauge will tell you that . . . .

Just my 2¢

HTH

Doc :beerchug:
 

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Registered
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2,119 Posts
Current Sensing Relay

We use current sensing relays on many of our systems. The relay changes state when it senses current flow on the feed conductor to a motor. If the motor is actually running it will trigger the relay. The sensor is a type of Current Transformer. Only way to really know that the motor is running but will not tell you if the pump is bad.

http://www.macromatic.com/literature/catalog/pdf/cxh-series.pdf


I have an electric water pump on my 351W engine. Does anyone know how to add a warning light which will illuminate if the pump is not running?
 

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Cobra Enthusiast
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57 Posts
I have an electric water pump on my 351W engine. Does anyone know how to add a warning light which will illuminate if the pump is not running?
RALPHV: Indicator lights that tell you that you're getting power to the pump won't do you any good, because they'll still light if the pump motor is open. What you're looking for is a DC current sensing circuit - a circuit that tells you the pump is drawing current. If there is no voltage to the pump, it won't light, if there is power to the pump and the pump shorts, it will blow a fuse, and if the pump is drawing normal current the indicator light will be on. AC current transformers won't work, since the circuit is DC. I'll do some research and see if I can give you a hand.... Jim
 

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Junior Charter Member
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1,146 Posts
It's an issue whether your pump is electric or mechanical - is there flow, or more importantly, am I keeping cool? Nobody likes to look down and see the needle pegged - and that can and does happen regardless of whether the pump is still working. A broken belt or loss of coolant are the main causes of most overheat situations.

An overheat alarm, visual and/or audible, does that job better.
 

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Cobra Enthusiast
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57 Posts
w4jeh - Thank you for your reply. It may be that your idea for a DC current systerm is appropriate. I will appreciate any further ideas.
The more I think about it, the better I like the idea of current sensing. It should be pretty simple - just add a current shunt (low resistance, hi power resister, ususally some sort of copper bar arrangement) in series with the pump and sense the voltage drop across it. If the pump is drawing current, there will be a slight voltage drop across it that you can use to activate a sensitive relay or switching circuit and light a led or activate a relay. If the pump isn't drawing any current, there will be zero volts dropped across the shunt and the led won't light (or the relay wont activate). depending on how fancy you want to get, you could use a relay to activate a loud alert, flash a warning light, or even limit RPMs with an MSD two-step. There are any number of possibilities, with a good imagination!
 

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Cobra Enthusiast
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57 Posts
Water Pump Indicator Idea

Ralph:

I've attached a diagram with my idea - put a low resistance current shunt between the negative lead of the pump and ground. If the pump is drawing current, there will be a small voltage drop across the current shunt which will be detected by the voltage sensing circuit, which will in turn operate a relay.
Depending on which contacts you use (normally open or normally closed) you can use the relay to either turn something on or turn it off. If you decide to pursue this method, let me know and I'll help you with the circuit.... Jim
 

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