fuse tap

[Herculean T4R]

Looking for a switched 12v in engine bay to power the relay that controls my transmission cooler fan. Basically, I want the fan to run when the ignition is on and stop when the ignition is off. Is there a way to use mini fuse tap in the fuse box that's located in the engine bay?

 

[MatthewRM18]

I would like to know as well.

 

[Jhelms]

What is the max current draw of the fan you plan to use?

 

[csp]

OP already stated he's going to use a relay. Current draw doesn't really matter in terms of his question, provided the circuit he's looking for is for triggering the relay.

 

[MatthewRM18]

Same here, I just need something to be the "trigger" for the relay, and like him, I was wondering if any of the fuses would provide that kind of signal. I know some do, I just don't know which one.

Sent from my VS990 using Tapatalk

 

[csp]

Its pretty easy to find a circuit in the underhood fusebox to see which are only hot with the key in run. All that's needed is a DVOM or a test light.

 

[TheDurk]

Its pretty easy to find a circuit in the underhood fusebox to see which are only hot with the key in run. All that's needed is a DVOM or a test light.

IGN, ECU-IG, WIPER, 4WD, TURN, GAUGE.

Is that enough? (It's all of them.) All by driver's knee.

None of those are under the hood. Those are all always on, on with ACC, or controlled by something else.

So, not so easy.

You could try to tap the output from the EFI relay at Terminal 3, which is triggered by key on ignition or in Start by the ECU (not recommended). But no fuse will work. Or tap inside by driver's knee (what I would do.)

 

[Jhelms]

OP already stated he's going to use a relay. Current draw doesn't really matter in terms of his question, provided the circuit he's looking for is for triggering the relay.

Missed that part on the relay Easiest way is to just use a dual fuse add-a-circuit. Any fuse that turns on via ignition on will work.

Amazon.com: Littelfuse FHA200BP ATO Add-A-Circuit Kit: Automotive

Or one can solder into the top of the fuse... Not what I would do however.

Last, there are fuse taps that cram over a leg of the fuse and into the fuse holder. I do not recommend these as they damage the fuse socket (only is an issue if the tap is removed at some point)

With the add on or solder on / pull the fuse and find out what side of the fuse position turns on with ignition. Make sure to orient the add on or solder on fuse so that the side you are connecting to is post fuse / not pre fuse. If it is pre fuse - bad things. Hope that makes sense.

 

[68ChargerJMP]

Agreed......add-a-fuse to the fuse panel by drivers knee...wiper fuse works for sure....very easy..Not so easy when trying to use a timed relay like I am and when you turn off the switch it sends ground back to my relay and unlatches it before the timer is up. ...frustrating.