03 berlingo 1.9 van fan blower works intermittently

It sounds like your blower thermostat is working intermittently.

Check engine temperature, fan operation and thermostat.
Also check inside blower operation. If intermittent, then check and/or change the blower motor.

Buy a new one....it's done....

sounds like the blower motor needs to be replaced.

Try installing a jumper across the N/O terminal at the relay socket. Temp sensor in the radiator or in the thermostat housing supplies the signal for the relay the other relay signal is supplied by A/C in on position. both fans will run continuous with A/C on. One fan runs intermittent relative to water temp. Be careful not to blow a head gasket. If you leave the jumpers in place, the fans will stop when the ignition is turned off, save the engine until you isolate the relay signal problem. then simply remove jumpers and reinstall the relays

Could be the blower motor, the resistor, or the control on the dash.
You'll need to check the circuit for voltage when it fails to work.

bad fan, also you have a bad ground for stereo

The power connection to the fan motor on these is known to overheat and cause a bad connection.The fan motor is above the passengers feet.Next time the fan motor will not come on, switch the selector to high and wack the bottom of the dash above the passengers feet.If the motor does come on at that time,you may need a replacement fan motor and connector.REPLACE the fan speed resistor board when replacing the fan motor,which is right behind the fan motor.

The wire that connects to the ignition switch that goes to the A/C blower fan is misplace upon connection.And its not grounded to any other lines.

There must be a relay for the heating system , in that case replace the relay.