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-   -   Wiring in a light to fuel pump system (https://vansairforce.net/community/showthread.php?t=96823)

Flying Scotsman 02-24-2013 12:15 PM

Which is why I use my checklist...1000' checklist includes "Fuel Boost Pump - OFF".

I don't trust myself to remember things :)

ao.frog 02-24-2013 02:29 PM

I have...
 
... done the same thing: wired a light so it comes on when the fuel boost pump is on.
I have installed an EXP-2 switch panel, so wiring the light was pretty easy.

I have also installed three more warning lights:
(right seat is pilot seat)




The warning lights are from right to left:
Red: low oil pressure
Amber: alternator offline
Blue: fuel boostpump is on
Green: defroster-fans are on

Robert M 02-24-2013 09:08 PM

Flap switch wiring with a light
 
Here is how my flap switch is wired. I don't suppose I can do the same thing with a light for my flap switch, can I - some how? I'm planning to use green lights. For some reason I got it my head that a red light means a bad thing.



I can't take credit for this image, I borrowed it from someone on this forum a long time ago and I can't remember who - sorry.

Yen 02-24-2013 11:58 PM

On a slightly different tack. I have installed LEDs across the fusesfor pump etc. Those LEDs don't light up unless the fuse has blown. That will show me if a pump is inoperative even if the switch is on.

krw5927 02-25-2013 10:37 AM

Quote:

Originally Posted by Robert M (Post 747417)
Here is how my flap switch is wired. I don't suppose I can do the same thing with a light for my flap switch, can I - some how? I'm planning to use green lights. For some reason I got it my head that a red light means a bad thing.

I can't take credit for this image, I borrowed it from someone on this forum a long time ago and I can't remember who - sorry.

If you use an incandescent light bulb for your "flaps operating" indicator you can wire it in parallel with the flap motor just like Brantel said above. Don't even need to pay attention to polarity. It will light up any time the motor runs, in either direction. A LED indicator would make things a little more complicated, but using 2 LEDs (one for flaps going up, one for down) would be rather easy - install them both in parallel but reverse the polarity of one LED in relation to the other.

I've never seen a "flaps operating" indicator in a panel though. Can you help me understand what the utility would be?

Mike S 02-25-2013 11:00 AM

The circuit that Brantel put up,



only shows that the power to the pump is on. The pump could be not working, or switched to an empty tank, yet the light would show pump on.

If you are looking to have an indicator that tells when there is aux pump delivering pressure, then you need something quite different.

For normal day to day use, the above should work just fine, but you should be aware of the little gottcha I mentioned.

ppilotmike 02-25-2013 01:19 PM

Tell us more...Mike.
 
Mike,

Your comment above has merit. The real reason we want the light on the pump is to know that it's working, not just receiving current. How would you suggest wiring something up to see that the pump is actually delivering fuel (pressure transducer or something in line?)

Mike S 02-25-2013 01:40 PM

Well, if you have a fuel pressure gauge, you already have the info available.

If you want a warning light, a simple pressure switch in the fuel line will do it, but then you are inducing another possible leak location. Vans supplied pressure sender manifold can handle this chore.

If you really want to go custom, a DPST pressure switch could easily be rigged to show Green for pump on and pressure present, or Red for pump on no pressure.

My main purpose in the prior post was to alert folks to the fact that an indicator light "ON" doesn't necessarily mean there is pressure.

For what I would use such a light, it would be to remind me to turn off the pump after take off.

JonJay 02-25-2013 02:34 PM

For what it is worth, most of the fuel pumps in our RV's are "continuous" duty rated. If you don't catch it with your checklist, catch it with your scan. If it runs for a while what's the harm? Maybe Don can chime in on his pumps?
If you do install a light for whatever purpose, have a means to check the light. Also, make sure it dims. One of the factors that led to an accident recently was a display that did not dim during a critical time of the flight
There is no free lunch. Everything added to your system is another point of failure and one more thing to manage.
You can tell I don't have a boost pump light huh?:)

Bill_H 02-25-2013 03:31 PM

To be really picky about it, the circuit shown only indicates that there is power to the indicator light. The branch of the wire to the pump could have a break in it.


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