Is there a convenient wire to power an engine on enable relay?

I need to replace my fan clutch when rainy season is over. Yet I need cooling for fast idling & hills.
I use the AC fan as a backup. Yet the 20 A fused tap is right to the battery.

Is there a good candidate to tap off of for a relay? It only needs current fot its coil. I would prefer a location in the engine area.

Thanks people.

You could always tap into the alternator's harness and get the 12v D+ signal when running. Wire that to the relay, and the fan would come on as soon as the engine were to start.

A less critical component to mess with is the Fuse #7 horn power. The horn is powered with key on and operated by a switched negative.

The diagram and some info is here.

https://sprinter-source.com/forum/showthread.php?p=278955#post278955

vic

I agree.
The D+ signal to the alternator comes from the instrument cluster so the chance of overloading it are higher.
The horn’s feed wire comes off a relay so has much more spare capacity to tap into.
[Edit: FB#1, Fuse 7 is fed directly from the ignition switch, not (as I thought) from the aux equipment relay... Thanks for keeping me on my toes, Vic!]

Be careful you aren’t back-feeding something else by hot-wiring the a/c fan... the ATC may be perturbed seeing it power up?

(on that note, the ATC harness likely has a signal wire you could feed/ground to trigger the fan on from the cab?)

-dave

Nautamaran said:

...
The horn’s feed wire comes off a relay so has much more spare capacity to tap into.
Be careful you aren’t back-feeding something else by hot-wiring the a/c fan... the ATC may be perturbed seeing it power up?

...

Click to expand...

FWIW. The power to the T1N horn is direct from the Fuse #7 15 amp. The relay switches the negative.

vic

I like the horn!
Thanks to all of you.

You're in the US, so there's a 99.99% chance that your Sprinter has the EK1 terminal strip under the driver's seat.

Three posts, providing three fused sources:

What it looks like and what they provide:



Where it is under the seat:



Where it is compared to the Parking Brake handle (see the screws?)



--dick

autostaretx said:

You're in the US, so there's a 99.99% chance that your Sprinter has the EK1 terminal strip under the driver's seat.

...

Click to expand...

Good point.

The Aux Electric Fan relay is under the driver seat so all of the wiring and even the switching can be accomplished without going out under the hood.


If the optional relays aren't there, there certainly are other choices for engine running power to be found under the seat.

vic