2017 strange heat issue

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plumcolr

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2017 with auxiliary rear heat, not with auto temp control. Not getting hot coolant to either front or rear. If I make a sharp right turn, coolant gets to the two heater cores momentarily then stops. Also functional for a short time on startup, but only sometimes.
This thing has an "Auxiliary coolant pump" mounted by the front right valve cover which takes coolant flow and boosts it to supply both cores. I don't think units without separate rear heat have this pump.
I suspect either a broken wire somewhere or a bad ground connection but cannot pinpoint. Have checked the connector but not with a meter yet.
Also cannot find a listing on ford parts sites for this "auxiliary coolant pump". Anyone have any ideas or experience with this?
 

Brandonian

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On my 2016 when purchased, they claimed they replaced the water pump - less than 3 months later water pump leaking (bought used at 140k miles 3 months ago lol) - took it in to them saying what the heck, and they called me back saying they replaced the auxiliary water pump not the mechanical one....to which they gave me the part number of what they replaced as fl1z18d473a - after looking it up it is the auxiliary water pump (didn't find where it was yet since it's not an issue for me, knock on wood) - so that should be the same part number for the 2017 as well, and it's not just for rear controls that auxiliary water/coolant pump is what allows the heat to circulate without the vehicle being turned on and up to temp and why warm air will come out quicker in the winter etc. from my research - It's also an electric driven pump...so check alternator etc. as it's electrical could stem from a number of problems, but you'd know if it was failing, the electric ones last a very, very long time from what I've researched on them, compared to mechanical.
 
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