Radiator fan on my 2001 pt cruiser only engages when the air conditioner is on. When the heat is on the fan doesn't work causing the car to overheat. Do I need a new fan?

Overheating is caused by:
1. plugged radiator core
2. Wrong mix of water and coolant.
3. Low coolant level.
4. stuck thermostat
5. hoses collapsing.
6. Air lock in system
7. Bad fins on water pump.

waterpump has died by the sounds of it

Blocked radiator, have it serviced.

check your fan relays and temp sending units...turning on the heat will help dissipate heat from coolant. turning on a/c will engage secondary cooling fan...check your relays and sending units

Turn ur car on defrost and check to c if fan is running. It should kick on on defrost. If it does not try checking fan or relay or your fuse. If of does and still gets hot maybe a good coolant flush will work.

I would be looking at the radiator fans themselves, especially if the fans are open
framed motors. I had the same problem with an intermittent fan on a PT cruiser,
If your A/C doesn't seem to be working right at stop lights then the fans are
most likely not operating correctly since they assist the condensing coil when idling.
Second thing I would suspect is a thermostat which is stuck closed. (This will cause overheat).
Hope this is helpful.

Three quick ideas. Make sure the vehicle sits overnight and check the radiator fluid level
in the radiator itself. If it gets low you will get an air pocket causing overheat. Also check
the reserve tank to be sure it doesn't have a crack or a hose fallen off which would cause an air pocket in the engine block by emptying fluid instead of recirculating. There
should always be fluid in the reserve tank.

Second, radiator cooling fan not coming on. If your air conditioner is not working well at
stop lights, then this is usually the culprit, since the fan helps to move air across the air conditioning coils. Everybody replaces relays but generally it is the motor becoming intermittent, since they are open framed and exposed to the elements.

Third is the thermostat may be stuck in the closed position, which will cause overheat.
Hope this helps.

Ensure coolant system has been properly filled.
Carry out all air bleed operations as specified by the manufacturer- (don't forget to open the heater core supply valve).

did you check the fluid level by removing the rad. cap? Radiator should be full to top. If Chryslers are low on coolant, the heater will not blow warm air.

I also own a 2001 pt cruiser and i am currently having to same problem. We have found that it maybe the radiator is clogged up or is clogging. This may possibly cause your radiator to crack ( mine has) . If you find an answer please post the solution.

Thanks