Trunk wiring question

[d0n_3d]

I'm trying to get a 12V source to four 30 amp relays mounted in the trunk (3 fans and an external fuel pump). Which wire or wires carry a 12V signal in the trunk? Can I tie all 4 12-volt relay wires into one and feed it to one single 12V source wire?

Also which wire is used for the factory fuel tank sending unit signal that goes to the fuel gauge in the dash? I want to connect my fuel cell sender to my fuel gauge in the dash (so I know how much fuel I have). It is a 0-90 ohm sender.

 

[novaderrik]

i don't think there is any kind of a constant power wire that goes back to the trunk- and if there was, i don't think it would be up to any sort of a load.
you will need to run one yourself, which would be just like running a stereo amp power wire.
as for the gas gauge wire, i think it's a tan wire. just try quickly grounding out wires until the gas gauge quickly pegs full- the one that causes the gauge to jump is your sender wire.

 

[pacecarta]

the fuel sender wire on the 87 is the pink wire at the center terminal of the three wire fuel pump connector, you should be able to find it at the connector in driverside rear quarter panel drop down

 

[d0n_3d]

Pink wire for sender...got it. Thanks.

I know I have to run a power wire straight from the battery to the relays, I'm just wanting to activate the relays with a 12-volt source in the trunk (the smaller gauge wires on the relays). Can't I just tie all 4 of those trigger wires together and connect it to a single 12 volt source wire in the trunk somewhere? I'm just trying to eliminate as much wiring as possible.

 

[pacecarta]

Pink wire for sender...got it. Thanks.

I know I have to run a power wire straight from the battery to the relays, I'm just wanting to activate the relays with a 12-volt source in the trunk (the smaller gauge wires on the relays). Can't I just tie all 4 of those trigger wires together and connect it to a single 12 volt source wire in the trunk somewhere? I'm just trying to eliminate as much wiring as possible.

do you really want the pump relay active all the time when key is in run position ? , its relay should be tripped by the ecm prime wire ...use the old stock pump feed wire at the trunk to power the relay and run a new wire for the new pump (or just use your old hotwire feed) , and for a cell I'd also want a seperate shutoff as well in the car and connected to the power cutoff switch at rear of car

the others i see no problem running the other relays solenoid source off a single wire from ign source

and why run the fan relays in the rear , makes for some longer runs of heavier gauge wire to power the fans , easier to pull those power feeds from the connection at the starter or battery (if still up front) or the splice before the starter if battery is in trunk ... and have the solenoids under the hood or at the fans

oh and another thing do you really want relays in the trunk that could have gas fumes in it

 

[d0n_3d]

I guess it does make sense to mount the fan relays in the engine bay next to the battery. I was just trying to clean up the engine bay some and also protect all the relays inside the trunk. I'll move them up to the front. I'll keep the fuel pump relay in the trunk though. There shouldn't be any fumes in the trunk because everything is sealed and plus I'm venting the cell through a hose that goes to the outside (near the back bumper).

Plus I forgot that I have to run a trigger wire from the FAST harness inside the car to the fuel pump relay in the trunk. I'm not using a factory ECM or harness. OK everything makes sense now. Thanks for the info.

 

[Bent6]

FWIW - I would not put fan relays in the trunk. Fans are one of the heaviest amp drawers in the entire electrical system and you don't want to have to draw that kind of amperage from one end of the car to the other.

You can pick up a constant 12v source from the trunk light - it is constant with the light housing having a centrifugal switch that turns it on and off. This circuit could only handle a light addition such as the relay positive triggers - you would have to switch the trigger grounds to activate/deactivate the relays. If you are using a FAST system with a Capsper adaptor for the stock harness, you can just catch the grey wire (behind the bumper that's in the same harness as the fuel level sending unit) for your relay ground trigger instead of having to run addtional wiring.