My heater on my reanult fan keeps cutting out

Sounds like you have a bad thermocouple, it is a safety device on the heater that will turn of the heater off to prevent over heating and cause a fire. If you jump across the leads your heater will work that will conferm that the thermocouple is not work and needs re-placed.

On all speeds? Next time it cuts off give the area below the glove compartment a good RAP upwards,if the fan motor starts,change it and the connector to it.

run the fault codes to determine the area of fault
could be cam/crank position sensors, immobilizer, ignition control module or broken timing belt/chain

rear brake caliper pistons usually need to be turned clock wise as being pushed back can get a tool from most auto factors not expensive

sometimes,and some cars have a blower motor resistor that goes bad.Check and see if you have one,replace

THE FAN IGNITIOR MIGHT OF WENT OUT CHECK IT AND TEST IT IT ALSO COULD BE THE RELAY SYSTEM SWITCH

POSSIBLE REHOSTAT PROBLEM THIS CONTROLS HAEATING FROM LOW TO HIGH

there is a short to circuit

The blower control module needs to be replaced. This will fix a ac, heater fan that runs all the time.

is your heater set on defrost this will cause your engine fan to run because it turns on the compressor for air conditioner this helps to extract moisture from your warm air defrost  and the fan in the engine compartment helps keep it the engine cool from the extra load on the engine this is normal