Tap fuse for engine rather than ignition

LJDC

LJDC

TJ Enthusiast
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It’s common to tap an ignition-on fuse, which tells you whether the key is in the ignition and the Jeep is running or set to ACC.

Is there a fuse to tap that will be on only when the engine is running (in my 2005 LJ)?
 
No (probably). Everything I can think of that controls anything to do with a running engine is powered up in "Run" and then controlled by the PCM by providing grounds.
 
On newer Jeeps you can use the heated seats. Obviously not the TJ.

What about the ABS relay for a Jeep without ABS?
 
LJDC said:
It’s common to tap an ignition-on fuse, which tells you whether the key is in the ignition and the Jeep is running or set to ACC.

Is there a fuse to tap that will be on only when the engine is running (in my 2005 LJ)?
Click to expand...

The only one we could think of that was easily tapped was the fuel pump. We set up a relay to only allow the large ARB compressor to run when the engine is running. Obviously it will enable when the key is first cycled to ON when the fuel pump runs for a few seconds, but after that, only when the engine is running (hopefully).
 
mrblaine said:
The only one we could think of that was easily tapped was the fuel pump. We set up a relay to only allow the large ARB compressor to run when the engine is running. Obviously it will enable when the key is first cycled to ON when the fuel pump runs for a few seconds, but after that, only when the engine is running (hopefully).
Click to expand...

Nice, thanks. That’s exactly the reason I want it. (Also for the winch.) My plan is to use the tap to power the switch, so it can only be switched on when the engine is on.
 
LJDC said:
Nice, thanks. That’s exactly the reason I want it. (Also for a power-hungry accessory in cargo.) My plan is to use the tap to power the switch, so it can only be switched on when the engine is on.
Click to expand...

Is the switch controlling a relay?
 
mrblaine said:
The only one we could think of that was easily tapped was the fuel pump. We set up a relay to only allow the large ARB compressor to run when the engine is running. Obviously it will enable when the key is first cycled to ON when the fuel pump runs for a few seconds, but after that, only when the engine is running (hopefully).
Click to expand...

What exactly did you tap to do this—a wire running to the fuel pump? I tried to tap the fuse, and then I realized that all of the fuses are always on, and everything is controlled by relays.
 
Another thought might be to use a thermostatic switch, into the coolant line or oil temp.

Nevermind, I see the problems with that. Unless, you use an ignition controlled AND the thermostatic but then it will start getting into a spider web of wiring.
 
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For an ignition source, there is wire that feeds the coil side of the ASD relay and I believe AC compressor. On my 2003 it’s a blue wire.
 
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