Thread: ID this relay please

The only difference to an ordinary relay is that the output (87 and 87a) is selectable when you turn the relay on and off. It is more likely that it switches to the secondary fuel sender (87) and the power used to turn the relay on goes on to power the secondary fuel pump. 87a goes to the original fuel sender, 30 to the fuel gauge. 86 is the line from the switch to the fuel crossover pump.

So how do I know which of the terminals on the relay are which ?

My intention is to run a seperate fuel guage for the aux tank so I need to id which is the input from the aux tank sender.

And have a switch to operate the pump directly (thorugh an appropriate relay if required - what would be?).

There is also alight which (in theory but not currently in practice, but did in the past) lights when the aux tank is dry, so one knows to turn off the pump.

I'm not sure why a fuel quantity sender might have a relay. Others might know...

Originally Posted by VladTepes

So how do I know which of the terminals on the relay are which ?

My intention is to run a seperate fuel guage for the aux tank so I need to id which is the input from the aux tank sender.

And have a switch to operate the pump directly (thorugh an appropriate relay if required - what would be?).

There is also alight which (in theory but not currently in practice, but did in the past) lights when the aux tank is dry, so one knows to turn off the pump.

Have a look at the piccy on the relay. The relay coil (-) should be earthed. The relay coil (+) 12V power should come from a switch. The path 30 to 87 is connected when the relay is "on". The path 30 to 87A is what is connected when the relay is "off". If the relay is "on" with a pump from the aux tank,then the aux gauge sender would connect to 87, the main tank sender to 87A and the fuel gauge to 30.

The terminals should all be marked with those numbers underneath the relay.

Originally Posted by IGL002

I'm not sure why a fuel quantity sender might have a relay. Others might know...

So that you can use just one gauge and select which tank you want to monitor.

While I agree with whats been posted for the wiring I have 1 concern.
The red jump wire from maybe 30 to the activation coil.
It may be a common earth or power but not sure why.

Which colors are on the mentioned terminals?
Is it all activated by one switch or is there a second for the pump?
What color wire is going to the 2nd pump?

Originally Posted by bee utey

Have a look at the piccy on the relay. The relay coil (-) should be earthed. The relay coil (+) 12V power should come from a switch. The path 30 to 87 is connected when the relay is "on". The path 30 to 87A is what is connected when the relay is "off". If the relay is "on" with a pump from the aux tank,then the aux gauge sender would connect to 87, the main tank sender to 87A and the fuel gauge to 30.

The terminals should all be marked with those numbers underneath the relay.

^x2

Standard automotive relay (5 pin), as per these following pics and article.

Some come with only four pins where 87a is left off (the pin in the centre),


Relay Basics

slug burner - that relay basics link was very good, thank you.

To clarify and maybe be of assistance,

Here are a few pics of the switch.





It's a 3 position switch.
Centre (off) - fuel guage reads main tank. Pump off.
Switched to "G" - fuel guage reads aux tank, Pump off.
Switched to fuel pump picture - fuel pump ON. Fuel guage reads main tank (IIRC)

I want to end up with each tank sending to its own guel guage.
A switch that runs the fuel pump.
A light that lights when the tabk is empty.

What wiring set up would I need to use for that, do ya reckon.