New guy. Fan question

[rose62]

Are you 100% positive you don't have any operation of Climate/AC/defrost active?

Pushed the power button for the climate control. Screen indicates that all is off.

Edit: Started it this morning. CHT at 124F. Swapped relay 89 with 91. Fan did not start immediately but did come on after about thirty seconds. Head temp still below 150F. Turned off the engine and swapped the relays back to their original position. Restarted the car, removed 91 then slowly reinstalled and I could feel the relay opening and closing.

So, the fan is being told to come on. Perhaps I should just not worry about it, but it didn't do this before.

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[ORRadtech]

I would personally worry about it and want it corrected.
Fans running all the time could keep the engine temp below optimum which can affect all kinds of things from engine longevity to emissions to performance to fuel economy, etc...
If you intend to work on your own modern cars then you really need a scan tool, preferably bidirectional.

 

[Cory S]

I would personally worry about it and want it corrected.
Fans running all the time could keep the engine temp below optimum which can affect all kinds of things from engine longevity to emissions to performance to fuel economy, etc...

Thermostat regulates that.

 

[PoCoBob]

If the fan is coming on after 30 seconds of running I would check the temperature sensors. That is way too quick for anything to heat up to the point of needing the fan.

 

[ORRadtech]

Thermostat regulates that.

Maybe. But the computer is getting false information which means it will try to compensate by adjusting air fuel, timing etc which will result in exactly what I posted.

 

[Cory S]

Maybe. But the computer is getting false information which means it will try to compensate by adjusting air fuel, timing etc which will result in exactly what I posted.

You have a better chance at seeing God than that happening. Engine is at operating temp even with the fan on. The factory 195° thermostat will keep it above 160° minimum operating temperature whether the fan is on or not…….

 

[rose62]

A/C is discharged. Must be damaged from the metal hitting the front end.

 

[Mike Pfeifer]

You have a better chance at seeing God than that happening. Engine is at operating temp even with the fan on. The factory 195° thermostat will keep it above 160° minimum operating temperature whether the fan is on or not…….

Maybe, maybe not, but it will surely cause extra unnecessary electrical load / stress. I’ve seen plenty of dead batteries due to fans being stuck on high all the time (not on mustangs specifically). Don’t expect the alternator to keep up with that demand forever.

 

[Mike Pfeifer]

A/C is discharged. Must be damaged from the metal hitting the front end.

Very likely damage to an AC line or condenser / drier. Might want to check any wiring behind there as well.

 

[rose62]

Very likely damage to an AC line or condenser / drier. Might want to check any wiring behind there as well.

Would it make the fan stay on?

 

[Mike Pfeifer]

I’m not familiar with how ford does it, but here in BMW world, if you empty the AC system it will make the fan come on full speed. There is a pressure sensor that detects the zero pressure and for some reason that is interpreted as a request for full fan speed. Actually, I think it’s interpreted as a short to ground in which case it doesn’t know the pressure, therefor the fan should run as a fail safe so the system doesn’t blow up due to possible over pressure.

 

[Mike Pfeifer]

I think the key here is that it was fine before the damage, and now it’s not. The damage is probably the cause so it should get checked out. Don’t overthink it.

 

[boB]

I designed circuitry for 12V HVAC systems, the compressors we used specified a pressure switch that would disable the clutch at either low or high system pressure. Ford may do the same.

 

[Vlad Soare]

Would it make the fan stay on?

Yes, it would. I also suspected something like this - see post #14.

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