The heater fan on my 1990 ford festva l plus will not turn on

Check for voltage and ground at the fan connector, with hvac turned on. If good voltage and ground with no fan action, suspect the fan. Use a testlite. Did you check for voltage at the applicable fuse circuit? Even if the fuse is good, if no voltage, the circuit is still dead.

dose it crank at all ?

clog heater core,thermostat open,water pump.

try turning the key as far back as you can before it shuts off. that works for mine.

My best advice for you is trying to find one at a junkyard. I can't think of anyone that carries battery post. It's either that or buy a new battery. Junkyard will save you money.

do you mean the FAN, could be the switch controling the fan. try that first, pulling the fan motor and heater core will be a pain.

The fan switch itself is a possibility, but there is also a resistor pack behind the glove compartment. Hi speed doesn't use the resistors, though, so if it doesn't run on hi, it narrows it down to the switch, the motor, the motor ground, or the blower relay, or any of the associated wire connectors.

look in the passenger footwell. if there is any moisture at all then the cowl drain around the windshield wipers is cloged. I know oyu think this is irrelavant but it is. If water is comming in then it has to pass right over the heater fan. so your fan motor may have been reduced to a ball of rust.

check to see if you can spin the fanwhile the engine is cool it should spin freely,if it doesnt fan clutch,also I would switch the fan back to oringinal just to test if this is the problem,if it is youll have to design a different fan shroud if you want to use you new fan,if everything done above is ok with the engine cool take off the radiator cap and squeeze the bottom hose 4-5 times in burst this will make sure you dont have air in the system,if this is helpfull please vote me a fix ya

heater is not trun on but the light in the heater painel is on can you help