Frank,

Since you are already familiar with the flapper valves, you are aware of
the source of the heat. Cool air passes through the exhaust heat
exchangers, up through the tin tubes and into the flapper valves, where it
is exhausted to the outside when the heater is off, or allowed to the noise
dampers (those black accordion looking things). One of two things has
happened.

A) your heater cables are out of adjustment. -move the heater lever fully
OFF, but adjust the lever to direct heat to the defrost. Start the motor.
Rev the motor to about 2,000 and put your hand over the defrost vents. Any
heat? If No, it is just hot in Arkansas. If yes, move to step two.

Step 2 with the motor still revving and your hand still on the defrost,
move the heater lever to fully ON. Was there a big change in air flow? If
no, your flappers are stuck. If yes, your cables are out of adjustment.

If the flappers are stuck, it is usually a sign that it is time to take
them down, remove the rust flakes, soak them in Naval Jelly, wire brush
them, paint them with 10 coats of Barbecue paint, oil the pivots, and put
them back on. Of course, this is good PM as well.
If they are out of adjustment, simply move the heater lever to completely
OFF, and then roll under the van. Locate the cable that leads to the wee
lever on each valve. Notice the little nut you can loosen to adjust the
cable? Well, go to it! Make sure the valve is completely closed, and will
also fully open when the lever on the dash is fully ON.

If all else fails, and you are at your wits end, Remove the flappers
altogether for the summer, and cap off the noise dampers with duct tape. DO
NOT cap off the tin tubes leading up from the heat exchangers, as they need
to allow the heat to escape. Be aware that if your flappers are off, any
water you drive through will be splashing onto you expensive heat
exchangers through the open tin tubes, contributing to their demise.

Cheers,

G. Matthew Bulley
Bulley-Hewlett & Associates
www.bulley-hewlett.com
Cary, NC USA
888.468.4880 tollfree