Horrible Smell coming from ac vents HELP PLEASE :)

a horrible smell is coming from the vents in the van it goes away when the ac if off and just the fan is running but as soon as the ac is on it smells horrible. does anyone know what to do to fix this?? thanks
Mike

The smell is usually caused by moisture buildup......and mold, etc.
You might want to make sure that the drain is working......you should get drips and a puddle of water on the passenger side of the vehicle.....inline with the firewall.
If the water is not draining at this location, then it could be draining someplace else.....like the interior carpet, inside the firewall....etc and be causing a moiture issue outside the air ducts......and these steps will not address that.

Set the A/C controls to ON....so that it is drawing air from the outside.....I think this is the regular A/C setting......(Max A/C recirculates the interior air only).
Use 1 of these 2 products.....Lysol or Febreze.
Spray the product into the intake vents that are located by the base of the windshield......the spray will be drawn into the air ducts.

If that does not work.....

The FORD TSB # for 1995-1998 windstar is 02-11-7
This is the same TSB as 99-19-6....with the addition of the advise to wear chemical goggles.
They have you spray Motorcraft A/C System Disodorizer YN-18 in the amount of 8oz.
For the Windstar, the product is applied into the blower motor housing.
They have you use a special tool to apply the product.....I don't know any details of the tool.

They also have a Moisture Purge Module (MPM) available.....part number for 1995-1998 is
F8XZ-19980-AA for the Moisture Purge Module
F78Z-14K095-BB for the wire harness kit for the Windstar

The MPM runs the fan after the vehicle is parked....to dry out the evaporator core area.
If the odor is from another location, this will not address that.

thank you for your fast response. we will try this. God bless :)