Radiator fan, ac, overheating problem. erradic operation of ac and radiator fan. therostat has been replaced, radiator, hoses and water pump are relatively new. radiator fan was replaced due to old radiator fan failure. new fan has always been erradic in actuating high and low though the fan tests good. now ac runs cold and not so cold. when ac runs warm engine overheats.

overheating? has many causes., if IS?
yes with A/C ON sure.
sure going fast the radiator cools better (higher gears)
OVERHEATING SIGNS ARE WHAT;
BOIL OVER? OR JUST DASH GAUGE TOo HIGH?
coolant leaks to ground or to front passengers toes?
5 year old hemostat should be good
fans kick on , at rear of radiator or are they dead?
off hand blind and deaf, the fans failing, on this 2017 car.
check fuses yet?
scan the PCm for fan errors or?
more causes
1: dead bugs plastered to radiator or front AC condenser. (back blast it with water hose nozzle)
new RAD do check condenser, same fix, cleaned.
2; belt slipping to water pump.
3: water pump impeller rusted to 1/2 its normal size
4; fans fail.

Could be any or all three or a bad cooling fan. I'd start by replacing the thermostat since they are dirt cheap. After replacing the thermostat warm the vehicle up and feel the upper radiator hose if its hot the rhe thermostat opened and the water pump is circulating coolant next check the radiator it should be hot near the upper radiator hose and significantly cooler near the lower with an even heat distribution if any parts of the radiator dont get warm/hot then you radiator is plugged. Also you need to check the operation of the cooling fan with the engine warm turn on your ac that should immediately turn the electric fan on

!st check and make sure the water is flowing in the radiator, then check
the timeing, Mazda will run hot if the timeing is rong.

When the radiator was replaced, I would assume that the cap has been replaced as well. Radiator caps that have worn out release steam from the system which means lesser water being circulated. Check if your coolant/water decreases. It may be a leak from the hoses or the engine itself. The leak from the engine may be a bad water pump or the water pump may be bad and water is not circulated correctly. Check the also the fan if it is running once the engine has warmed up. Check the fuses for the fan and its relay. Swapping relays with the AC fan to test is one way of testing if it is the relay or the fan that could be bad.

Is the water pump leaking coolant? If not, then why do you think it's bad?

If the engine is overheating, there are several other things to look at before you consider the replacing the water pump.

Are the fans electric motor driven, or fan belt driven? If fan belt driven, replace the fan clutch. If electric motor driven, check the fan control module and/or fan motors to make sure all is good there. Fan control module tend to fail in weird ways, so if nothing is wrong with the motors, replace the module.

Always, always, replace a thermostat that has overheated. Once overheated, they consistently fail. Make sure you properly refill the radiator with coolant after the stat is changed.

Check that the bottom radiator hose does not collapse.

Check the radiator for corrosion. Boil the radiator out, or have it done, or replace the radiator.

You might wann replace the coolant, and also check the radiator fans, if they are working or not.

If the hoses, radiator, thermostat,radiator, and water pump are working properly and the overheating is being caused by the cooling fan not operating, then I would check the relay for the cooling fan with a multimeter. If it is ok, I would look at the coolant temperature sensor. Hope this helped.

you might need to add water to your radiator

many things could cause the overheating. broken water pump impeller, stuck thermostat, clogged radiator, inoperative cooling fan on the radiator.

i would first check to see if the cooling fan on the radiator is working. when it reaches operating temp (or surpasses it in your case), see if the fan attached to the radiator kicks on. if its not on, then either the fan has failed or the temp relay to kick on the fan has failed. also, make sure the connector is plugged in.

after its at operating temp, turn off the car and feel the radiator. if you feel cool spots, then it is clogged and needs replacing.

wile under the hood and car is off, feel the upper & lower radiator hoses. if one is hot and the other is cool, then either the water pump (actually the impeller on it) has failed and is not circulating coolant through the radiator. a common problem in this model.

but it could also be the thermostat. if failed, it would not allow coolant to flow & circulate.

hopefull one of the above items is the problem. good luck.

Hi! Was the thermostat and other items replaced due to this overheating? you say coolant level full? maybe your header tank is full but the system isn't? Try bleeding the system. From cold, start the engine with radiator/header tank cap OFF stay with the vehicle and have some very warm water handy. DON'T look over the filler but watch it as the car gets to operating temperature if the water drops drastically top it up with warm water again stay with the car it may take a long time to level out. If the car is bubbling furiously and doesn't want to settle then possible HEAD GASKET Failure or Water pump.
Does your oil look milky on the dipstick? is there an excessive amount of water coming out of the exhaust? are your hoses swelling with radiator/header tank cap on at operating temp?
Sorry to be the possible bearer of bad tiding if the Gasket has gone, but better to sort it now than cause irreprable damage?