Would would happen if both the heat sensor and the timed relay in this circuit sent power to the fan?

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Joined Jun 22, 2022
I am designing a circuit for a timed relay to power a fan, and I drew out the circuit in the attached image. I have given a lot of context below, but the TLDR is that I am wondering if two different paths from the same DC source are activated, would that short something or cause a problem? Thanks

My car has a secondary electric fan that comes on when the computer detects that the car is too hot and needs extra help idling. That works for when the car is on, however on hot days, when you turn the car off and all the fans stop, the accumulated engine heat can damage wires. It is a common problem nicknamed "heatsoak" on my 1997 Jeep Cherokee. To resolve this, I am designing a timed relay circuit that will be triggered by a button on my dashboard. The idea is that if I have been driving for a while, once I stop I can hit the button, and the relay will direct power to the fan for an extra 10 minutes or so. I have drawn out the circuit in the attached image , but I have one question. What would happen if I accidentally press the button while the car is running and the fan is already on? I know this is probably not that complicated, but I am new to this and would like to make sure I do it right. Any help is greatly appreciated. Thank you!



Joined Mar 14, 2008
No problem doing that.
You just have two parallel wires with the same voltage going to the fan instead of one.
The fan won't won't notice the difference.