Heater fan only blowes on high what could it be

It will not correct fan speeds, you have other problems, perhaps heater core is partially blocked not allowing air to pass over fins. Look at blower motor resistors or high sped relay. good Luck.

depending on car some have a fan relay or its your switch itself

it sounds like the heater switch itself is bad. I would change it.

needs to replace the heater core

When the blower works only on the high setting its usually a bad blower resistor which is right near the blower motor. now you say it would always blow high regardless of the fan speed setting that would indicate probably the climate control unit or a connector problem somewhere. finally it not working at all may be the climate control unit or connection went bad even further. it might have a blown fuse or a bad blower motor in addition to the climate control unit or connector problem .check for power and ground at the blower motor. the power is supplied from fuses and may have a relay also. the ground is supplied from the climate control unit and goes through the resistor to control the fan speed. good luck

replace fan speed resistor block if this only happens on lower fan settings if it happens on high fan speed also, replace blower fan

When you say your heater, do you mean the fan does not blow. or no heat fan blows fine. If it does not blow. The fan is located in the passenger side footwell, Turn fan to high and wack it a couple of times on center of cicular lookin thing, easily replaced by removal of screws around outside. If the fan works fine and it blows cold air make sure temperature adjustment knob is workin fine, you should hear it change when adjusting. One other thing, if someone just flushed your radiator or anything similir to do with coolant, check for a air bubble in the system, purge air out of heater core lines with a garden hose.
good luck

Hello let me verify.
1 heater wont blow out warm air unless on high?
possible clogged airfilter.low on coolant or antifreeze.

2 heater wont blow any air unless on high?
Could be a bad switch low ane med do not work.

I believe there are TWO fuses for the heater blower. One for the lower speeds and one for the high speed ONLY. REcheck the fuses or refer to the owner's manual for the location...

Sounds to me like your heater resistor may be bad do you have any speeds on the fan because typicly you will still have high when this fails if so you may want to check fuse for heater and relay hope this helps