Cooling fan issue

[phishplate]

2014 Mustang GT. When my GT is at normal operating temperature and I am sitting at idle I have noticed that when my cooling fan engages it will cause my engine to bog down. It recovers and everything is fine. It will do this like clock work every time the fan engages. It will not do this if I am on the throttle. Found that out recently when driving in reverse and the fan kicked in. It has not cause any overheating issues, but I see this as a sign of a potential problem coming up.

Has anyone else experienced this issue?
Haven't had time to check, but I am leaning towards the alternator being the culprit.
Any help would be appreciated. In the mean time I am going to try and find out what my alternators output at an idle should be. The cooling fan is the only accessory to cause this issue. When at temp and idling the fan does kick in a lot. Been thinking about putting in lower temp thermostat, but I am not sure how much that would help.

 

[GN_Mike]

How much does the engine bog down? Like a hundred RPM? I’ve seen this happen on the cars I’ve owned that had large cooling fans. When the fan kicks on, there is a huge inrush of current required to start the motor. When that happens, the alternator goes to full output and drags the engine down a bit. The ECU should then compensate by opening the IAC to recover the idle speed. This should all happen in a second or two.

Is this what you are seeing, or is your engine nearly stalling?




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[phishplate]

It is as you described. It bogs down in that ball park. From what I am seeing on the Tach it looks like around 300. It does recover fairly rapidly from my unscientific count around 2 seconds. Never owned a vehicle that did this when the fan engaged. If this is normal then so be it but others I have talked to say their mustangs do not do this.

 

[GN_Mike]

I spent some time listening to my 2011 GT last night. When the cooling fan kicks on, I can hear my engine speed drop a tiny bit. The tach barely moves, maybe drops 50 RPM. If you are seeing a 300 RPM drop, something is wrong, I think.



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[Riddick]

Is your fan kicking on or is it your AC compressor clutch engaging? 300 is a lot for either but these cars are notorious for compressor clutch issues.

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[phishplate]

I do not have any of the climate controls on when this is occurring. Not even on with the fan speed set to minimum. I did find the out put info chart for my alternator just have to get time to check it. It is the original alternator. From what I am told Ford alternators can have issues right off the shelf. Would this be a situation where if I find there is a low output from my alternator I would want to swap it out for a Boss 302 alternator? I know there are some differences, but it seems that's what most people are doing when they have some issues arising. Are there any cons to going to a boss alternator?

 

[SHIFTYBUSINESS]

Is your fan kicking on or is it your AC compressor clutch engaging? 300 is a lot for either but these cars are notorious for compressor clutch issues.

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Mine is doing the same thing when the ac compressor comes on. I guess I'm gonna need a ac compressor?

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[railroad]

On the fan related concerns, have you battery load checked.

 

[phishplate]

OK, sorry I have not been back been kind of busy. I did check my battery and my charging system. According to the tests everything is good. Battery is healthy and alternator is charging at spec. Checked the fan as well. It spins feely with no hint of bind or drag. When I get time I will have to check my relays to see if they are doing well.