Auxiliary fan My auxiliary fan isn't coming on at all even when i put my ac on and it is causing it to over heat i have changed everything on the cooling system water pump and all. I also changed the fan relay and the fan switch did i miss something?

There could be a few possible causes for the rear heater not blowing hot air in your 2003 Chevrolet ASTRO van. Here are a few things you could check:

1. Make sure that the rear heater control valve is fully open. This valve is located near the heater core and controls the flow of coolant to the rear heater.
2. Check the coolant level in the radiator. If the coolant level is low, the heater may not be able to produce hot air.
3. Check for any leaks in the coolant system. If the system is leaking, it may not have enough coolant to produce hot air.
4. Check the thermostat. If the thermostat is stuck closed, it may not be allowing enough coolant to flow through the system to produce hot air.

If these steps do not help, it is possible that there is a problem with the heater core itself, or with other components of the heating system. It may be necessary to have a mechanic diagnose and repair the issue.

Check rear AC in van and turn it off. Most vans have dual AC. Even if the front AC is off, the rear is still usually on and some vehicles have the cooling fan and condenser fan run together to help with cooling. Check relay and fuse also.

If the fans work, (I'm guessing there are two of them) only when the A/C is on, then it means that the temperature sensor is damage. If possible, have a professional take a look at it. Both fans are OK,

Hi, Yes you have an air lock in your system, you may get this sorted by 1/. Removing one of the cooling hoses & try to blow with air.
2/. Drain all the system then put your heater on inside the vehicle & have the engine running & refill the system Start to do this from a cold engine. Please leave me feed back: Malcolm Campbell, Thanks.

Your airconditioning system may be out of cooling gas, and if it has sufficient gas, the compressor might not pick when you put on the AC, and if the compressor did not pick ie start, you cant experience cooling effect, the fan will only be blowing.

You need to stop using it immediately before you
cause some damage or more than you may already have
That is just common sense. It should not overheat or
be any different than it was in the past without problem

The car has to be checked over/diagnosed,tested,etc for
various issues to resolve

Borrow or Rent a car until resolved

No way to guess at the problem

You should have some type of codes avail even
if the check light isn't on,you need professional help
to get a start on resolving

The timing belt maybe worn & jumped or the head gasket
bad.

Over heating isn't usually a cheap repair unless the thermostat
sticks partially closed

The RPM moves around the car is 11 years old,so it may just
need a though going over

Timing Belt,O2 Sensors,Exhaust Converter,Spark Plugs
and such

If you depend on a repair shop to do things & don't
have the knowledge to request work done throughout
the year,then you run into a lack of proactive preventative
maintenance situation. Most things are simple looking
back, once resolved

Having to use the heater as a auxiliary cooling source simple tells use the cooling system needs a little help.
1. make sure the AC and Radiator coils are not plugged on the outside
2. let the car idle until normal operation temp is achieved, see if the cooling fan comes on
a. if not the fan is at fault
b. the fan sending unit is at fault
c. or dirty or broken wires

If the temperature goes up when the ac is on, then there may be a problem with the circulation of coolant throughout the system. You said you changed the thermostat which is good. But, did you backflush the engine's cooling system so that maximum flow can be achieved?

On the other hand, the heat that comes off of the condenser can cause the radiator to cool less efficiently on hot days.

Does the fan immediately go on when the a/c is turned on? or is it the older style fan belt driven fan? Even, so, if it's an older style fan, the clutch sometimes go bad in them so that the fan doesn't spin as efficiently as it should.

Also, did you use 50/50 Antifreeze to water ratio coolant mixture?
If you use pure Antifreeze 100% concentration, then it can cause an overheat condition, because the fluid at this concentration doesn't transfer heat as well as a 50/50 solution of antifreeze to water.

Good luck fixing this problem.

climate control units in most cars use the ac system to regulate temp in the cab. the ac system requires a fan to pull air over the condensor on the front of the car. its normal for a fan to come on. unless you have a bad engine temp sending unit thats causing the engine cooling fan to come on improperly. try turning off the heat and ac and see if it still comes on.

The accy fan you are refurring to is actually the a/c consensor fan.The only time that fan operates is with the cycling of the a/c system.Verify by turning a/c on ,fan should come on & off with a/c cycles..