2014 Fiesta ST overheating while idle when A/C is on

[MartinAbsalonMan]

Hey guys, just curious if anyone of you guys has had to deal with the same issue. So my 2014 Fiesta ST has been overheating while idle when my A/C is on. It runs perfectly fine when the A/C is off, the A/C blows cold air when the car is moving but immediately begins to blow warm air once I've stopped. I've found some general information on it but have not been able to pinpoint the problem. Any advice or possible fixes would be greatly appreciated.

 

[Woods247]

Your best bet is to swap the radiator and have Ford install a 180 thermostat under the recall. Mountune and Mishimoto make bolt in radiators that solve the overheating issues on these cars. You don’t really have any other option but to change it. It’s worth doing. The car is otherwise fantastic and mechanically reliable.

 

[Intuit]

Is your engine fan running? Unless it's too cold, it should activate with the compressor. (if it's too cold, the compressor won't activate)

 

[Ford ST]

If your AC gets warm when you are not moving that tells me that your fan is not running.

Sent from my LG-LS997 using Tapatalk

 

[PhoenixM3]

Any known tests for the fan control module. Don’t think my fan is ever coming on..... I have the colder thermostat but crappy stock radiator and have pegged the temp gauge in 94 degree ambient temps.

 

[M-Sport fan]

My car must be an anomaly, since it ALWAYS runs lower coolant temps when the air is on, even sitting still in 100*F+ temps, it NEVER goes above 190*F with the air on (factory radiator, factory tune, stock snail, 2016 model year, but 35% coolant/65% water with an additive).

My fan IS working, obviously, and this car does suffer from creeping temps when sitting still without the AC (and therefore, sadly, also without the fan) running, since the factory sets the no AC fan activation in the ECU at WAY WAY WAY too high a coolant temp for it to ensure safety, due to CAFE/fuel mileage concerns.

Even when moving, without the air on, it will run about 5* to 10* hotter than when moving with the air on.

The fan being operational in high ambient temps is life and death for this engine, regardless of the radiator installed. (But OF COURSE it will be better with one of the aftermarket radiators installed. )

 

[PhoenixM3]

My car must be an anomaly, since it ALWAYS runs lower coolant temps when the air is on, even sitting still in 100*F+ temps, it NEVER goes above 190*F with the air on (factory radiator, factory tune, stock snail, 2016 model year, but 35% coolant/65% water with an additive).

My fan IS working, obviously, and this car does suffer from creeping temps when sitting still without the AC (and therefore, sadly, also without the fan) running, since the factory sets the no AC fan activation in the ECU at WAY WAY WAY too high a coolant temp for it to ensure safety, due to CAFE/fuel mileage concerns.

Even when moving, without the air on, it will run about 5* to 10* hotter than when moving with the air on.

The fan being operational in high ambient temps is life and death for this engine, regardless of the radiator installed. (But OF COURSE it will be better with one of the aftermarket radiators installed. )

Not sure why your car is displaying these symptoms, but suddenly my car‘s fan is not working at all. I’ll start a new thread to avoid jacking this one. Good luck!

 

[Magnetic]

My car must be an anomaly, since it ALWAYS runs lower coolant temps when the air is on, even sitting still in 100*F+ temps, it NEVER goes above 190*F with the air on (factory radiator, factory tune, stock snail, 2016 model year, but 35% coolant/65% water with an additive).

My fan IS working, obviously, and this car does suffer from creeping temps when sitting still without the AC (and therefore, sadly, also without the fan) running, since the factory sets the no AC fan activation in the ECU at WAY WAY WAY too high a coolant temp for it to ensure safety, due to CAFE/fuel mileage concerns.

Even when moving, without the air on, it will run about 5* to 10* hotter than when moving with the air on.

The fan being operational in high ambient temps is life and death for this engine, regardless of the radiator installed. (But OF COURSE it will be better with one of the aftermarket radiators installed. )

That's [robably because when you have the AC on the radiator runs faster to deal with the extra temperature being added by the AC compressor. At least that's what it seems like to me.

 

[Ford ST]

That's [robably because when you have the AC on the radiator runs faster to deal with the extra temperature being added by the AC compressor. At least that's what it seems like to me.

It is to pull as much air through the condenser as possible. The more heat that can be removed from the condenser the better the air conditioning will work.

Sent from my LG-LS997 using Tapatalk

 

[Magnetic]

It is to pull as much air through the condenser as possible. The more heat that can be removed from the condenser the better the air conditioning will work.

Sent from my LG-LS997 using Tapatalk

Yes that totally makes sense!

 

[M-Sport fan]

That's probably because when you have the AC on the radiator runs faster to deal with the extra temperature being added by the AC compressor. At least that's what it seems like to me.

YES, OF COURSE.

But what is strange though is that the coolant temps never seem to climb above 190*F-192*F with the air on, idling (or even driving reasonably hard), no matter HOW torrid it is out, even in ambient temps above 100*F (UNLIKE everyone else who seems to get runaway coolant temps in those conditions, at least with the insufficient factory radiator, after the initial high speed fan coolant temp lowering 'hit' after turning on the air).

Maybe the coolant additive and low coolant concentration percentage I run really DOES have much more of a heat transfer effect than anyone gives them credit for?

 

[Magnetic]

YES, OF COURSE.

But what is strange though is that the coolant temps never seem to climb above 190*F-192*F with the air on, idling (or even driving reasonably hard), no matter HOW torrid it is out, even in ambient temps above 100*F (UNLIKE everyone else who seems to get runaway coolant temps in those conditions, at least with the insufficient factory radiator, after the initial high speed fan coolant temp lowering 'hit' after turning on the air).

Maybe the coolant additive and low coolant concentration percentage I run really DOES have much more of a heat transfer effect than anyone gives them credit for?

Out here in AZ my coolant temps can go over 200 at times. But it was like 115 outside.