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Hot wire under the hood

My cooling fan don’t work on their own I have it wire to a switch inside the car I want to move the wire so the fan run only with the car running so what a good place to tap into ? Thanks

There’s circuits that only are powered when the engine is running. Like the circuit for the fuel pump. The problem is that circuit might not be able to power both the fuel pump and the fans, which draw quite a bit of current themselves. If you tap into it and it can’t handle the load, not only will the fans not work, but the fuse will blow and the fuel pump won’t work either. Are you able to post a circuit diagram of the power distribution circuits. That might bring up some clues.

Is the cigarette lighter power on all the time or does it go off when the key is off? If the latter, you can tap into that.

Use a relay and then ANYthing that is hot when the car runs can power it. Wire the relay trigger side to any fuse that is hot in the run position. Wire the power for the fan to any battery terminal. The relay then acts as the switch to turn the fan on whenever the car is running.

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I have to ask the obvious (to me) question: why don’t the fans run on their own like they’re supposed to, I assume?

Say you do wire them up to a hot wire that you manually switch on and off. What happens if you forget to switch off the fans and run the battery down? Or burn out the fans?

Good luck.

One reason it wired to a switch is there no voltage from the 30A fuse to the relay if I jump it there the fuse is hot with the key off the relay is new the temp sensor is new and has 5 volts going to it

sorry, can’t make sense out of this, could you repeat with some proofreading please.

Why not try to find out why the 30 amp fuse isn’t getting power? Most likely just a bad connection to the main power bus in the fuse panel and a simple repair job.

Another problem with the radiator fan running all the time is the engine coolant won’t ever reach the optimum operating temperature, which can result in engine problems developing over time (soot, sludge, fouled spark plugs etc). Plus you won’t get the best mpg you could otherwise be getting. If you could post the schematic of the fan circuit, the folks here could probably help you debug it step by step.

I been running with no fan at all it fine most of the time but at long lights it get a bit on the hot side, not 100% sure why the won’t come on but part of the reason is a short in the fuse box there a 30 A fuse for the fan the fuse is good there 12V on both side of it but the fan relay has no voltage going to it at all none on any pin there should be 12 V at pin 87 I think that the number ,

right now I have a wire from a switch to the pin 87 on the relay

Then your problem isn’t due to a short, it is due to a faulty wire connection, most likely within a connector. I suggest you purchase a factory wiring manual for the vehicle so you can track down where the problem is at. A factory manual will show you where the connectors are at and makes troubleshooting much easier.

Relay pins are usually numbered like this

86 - 85 is the coil that operates the switch
30 connects to the battery (via a fuse), and 87 is the switched power to the fan.

When current flows between 86 and 85, the switch closes, which causes current to flow from 30 to 87 then to the fan. So if you have no battery voltage at any of those four relay pins when the engine is running, that indeed seems like there’s either a fuse or wiring problem, or another relay isn’t working. It’s definitely possible there’s a problem inside the fuse box itself. I had that problem with a VW Rabbit one time. Sometimes the problem isn’t inside the fuse box itself, but instead the connector that plugs into the fuse box has burned pins. If that’s the case, its often possible to do some minor rewiring, bypassing the burned pins. On the Rabbit replacing the fuse box wasn’t overly expensive, so cost that option out too. I took the old one apart out of curiosity, and inside there’s a bunch of quite thick & wide strips of metal that form the high current connections. The problem isn’t usually with them, it’s where they make a connection to the external connectors that plug into the fuse box.

Thank you it been a few week since I did it I have look but there are only 2 relays one for the fan. The other for the AC the AC relay has power to it