Negative switch relay

[kiwiscole]

I wish to run a 12v fan in the cabin of my car, only while the engine is running.
I wanted to use the alternator charge wire, connected to a relay, so when it switches off, the relay opens. But my car doesn't have such a wire on the alternator.

I'd like to use the oil sender wire.
This is a negative switch.

Can I wire a relay so that when the oil light goes out, the circuit opens? Either positive or nagative output is fine.

Thanks.

 

[brianmoooore]

Yes, but take the supply for the relay coil from the same fuse as the oil light.

 

[Soi disant]

Hands up who remembers the good old days when if you were selling a car with dodgy oil pressure you'd wire the warning light into the ignition warning one instead....

 

[DPG]

Must be an ignition live feed available?

 

[Soi disant]

I think he wants engine running, not ignition on. TBH I can't think why, as you're not really supposed to leave the ignition on with the engine not running for significant periods.

 

[PEG]

Hi,the make and model of the vehicle is important,in deciding the best method of achieving what the OP wants.

 

[Soi disant]

We can hazard a guess that it's probably an old one.

 

[brianmoooore]

We can hazard a guess that it's probably an old one.

So old it has a dynamo?? OP says it doesn't have a D+ terminal, so I assumed it was something modern with an AGM battery that needs fancy charging.

 

[Soi disant]

A modern Australian car with no air-con?