Why does my radiator fan stay on?

Hi Fred.

I'm not totally sure I understand your question, but I'll take a shot. Are you saying that the engine fan stays on all the time for your car, keeping the radiator cool, and so you're not able to get any heat in the cabin air? Or possibly that the cabin fan is on all the time and you can't get any heat because it's keeping the radiator cool.

unless there is something very odd about your car (or you're living at the south pole), your engine coolant will be plenty warm within a few minutes of starting. If you are doubtful, drive the car for 5 to 10 minutes, stop, turn off the motor, pop the hood, and carefully move your hand close to the radiator. The blower fan helps transfer heat, but that's to move the coolant temp down probably into the 150-200F range.

if you're not getting any cabin heat, I'd have stronger suspicion about the heater core for your air system. In the majority of vehicles, there is a loop of coolant that comes off the back of the engine block, through the fire wall, and up to a U-Bend of pipe. When the heater is off, the coolant is just re-directed back to the engine. As you turn the knob or lever for cabin heat, it'll turn a switching valve to shunt the hot coolant into a heat exchanger/mini-radiator that the cabin air blows past. This system being a mini-radiator is why highways with long uphill grades will advise motorists to turn on their heater full heat, highest fan, when climbing in the summer. it's an additional way to keep the engine from overheating, even if it sucks for people in the vehicle.

Depending on the car, it can be either easy or really involved diagnosing or repairing the heat exchanger. if you go this route, you'll want to make sure that the coolant is circulated through the core thoroughly and that the coolant-system is de-bubbled.

Good Luck!
D

Sounds like the heater core

Look for an air block in the heater core, or a water valve in the heater hoses that may be closed. The normal way to purge air from the coolant system is to run the engine with heater on high heat, and with the radiator cap off, until the thermostat opens and the engine is at normal operating temperature. Then shut off engine, top up the radiator and overflow tank, and replace the radiator cap. If hot coolant is still not circulating through the heater core, you may have to get inventive and crack the outlet line loose to get flow started.

bad heater core won't cause engine to overheat unless its leaking coolant and coolant level low, if car is running hot make sure your radiator cooling fan is coming on, fan won;t come on unless a/c is on or engine reaches 228 degrees

possible blend door in the dash is broke . when you turn blower on high it blows the door shut . i have the same issues and i have heard this could be the issue . especially since you said that you replaced everything except the blend door.

It's most likely a heater core leak. Hot radiator fluid is passed through the inside of the heater core, and air is passed over that. if there is a pin-hole leak in the radiator core, then it will come out of the vents. Turning off the heat setting will not change the leak either, it will still leak and collect in the lowest spot, and then blow out the vents when it strikes the fan impeller blades. the heater core is fed from 2 smaller radiator hoses. If you look under the hood, you'll see 2 large hoses that come out of the radiator. you'll also see 2 smaller hoses that go back towards the front of your car through the firewall. these 2 little hoses go to your heater core. Most cars require dash removal to change out the heater core. Unless you are pretty handy, I'd leave this one to the shop.

will it sounds like u tryed everything except what could be cousing the problem it is probley the heater core is pluged with hard water or calcium build up or is just pluged and a rad flush wont flush the heater core unless you start the vechial and flushing the rad to do the heaterd core to turn on the heat to high and the fasters fan speed and make shore the van is running.

Has to taken to radiator specialist to dismantle....however if its aluminium may be cheaper to buy new one.

First thing first, turn off the engine wait for 15 - 20 mints, open the radiator cap and fill it up to the top then start the engine and see if it needs more water adn add as needed, then wait till you ca see the water circulating in the radiator now instead of corculating if it starts boiling out shut the engine replace the thermostat and do the whole thing again.

unless there is water in the engine the gauge will not be able to show the actual temp of the engine, so always malke sure you have water / antifreeze

1st thing to check is the coolant level. I've seen cars w/ no heat, or very little quite a few times caused by low level in cooling system--not low enough to overheat the engine, but enough that circulation of coolant to heater core is affected (no or little hot coolant circulation to heater core=no or little heat),
Is the engine temp gauge in the normal range? If it's in the low range, engine not reaching operating temp. it could be caused by a thermostat stuck in the open position (or no thermostat, sometimes people remove them when their car overheats, and this should not be done).
Here's how the system works: the heater 'box' contains a heater core (a mini radiator) w/ a fan and hoses connecting the heater core to the engine cooling system. Hot engine coolant is circulated thru the heater core. When u activate the heat switch on the dash, a flap door opens to expose the heater box to the passenger compartment. The fan switch on the dash activates the fan, which blows air thru the core, which heats the air.
So, if it's not the coolant level at the radiator, the fan is obviously working, the engine is reaching operating temperature, I would say it must be the flap door that opens, isn't opening fully, or isn't staying open. It could be the dash switch is defective (not supplying current to open flap door) or less likely the flap door is binding somehow. Hope it's as simple as correcting coolant level, if not, the dash switch control should be checked