Double Relay for Electric Fuel Pump and Alternator Warning Light

[Haveacamper]

Hi All,

I've just been setting up a bench tester and I'll be running a Carter electric fuel pump. I've wired up the double relay setup for the fuel pump as per D.Whipps's wiring instructions here: https://earlybay.com/threads/fuel-pump-relay-and-other-starting-issues.82142/post-644333

What I have noticed is that when connecting the alternator warning light to relay, the warning light no longer lights up when my ignition is on (15 live). Is this expected?

FYI: I have tapped into the blue wire on the back of the warning light itself with a piggyback connector on the blue wire.

I think the blub is no longer lit with ignition live because when connected to the relay, I have 12v both sides of the blub?

Have I dont something wrong here?

 

[gagvanman]

This how I did this:

Relay 1 gets +12v on pin 86 from the starter / ignition when the key is turned to start. This energises the relay and routes +12v from the battery to relay 1 pin 87 which primes the fuel pump.

Once the engine has started and the ignition key returns to the acc position, relay 1 disconnects pin 87 and relay 2 gets +12v from the alternator ignition warning connection to energise relay 2 which routes +12v from the battery via pin 87 to the pump.

If the engine stops with the ignition switch still on, the alternator ignition warning supply to relay 2 pin 86 is dropped and the pump stops.

 

[Haveacamper]

Thanks for the reply and the alternative wiring solution.

I am still trying to understand though whether the wiring example provided by D.Whipp would, in fact, cause the gen light to be off in acc position (15 live).

The gen warning light receives 15 live on one side and blue wire on the other. BUT when this blue wire is also connected to the relay pin 86 and pin 85 also receives 15 live the warning light essentially 'sees' 12v on both terminals i.e. 0 voltage drop and therefore does not light up.

 

[67panel]

Pin 85 goes to ground so no you dont have power to both sides

 

[Haveacamper]

Pin 85 goes to ground so no you dont have power to both sides

Sorry, if you follow the link in the first post, it goes to a diagram created by D.Whipp which suggests double relay setup with 15 live to 86 and alternator blue wire to 85