Hey guys. I joined this forum to help my mom,
a mail carrier, figure out what the problem is
with the heater in her 98 mercury sable. The
heater is blowing out cold air, especially when
it is on the defrost setting. The fan is working,
but no heat. She has replaced the water pump,
thermostat, a thermostat sensor (if that exists?
)and has also flushed out the heater core.

What do you think the problem is? Thanks in
advance, any help or advice you have would
be greatly appreciated so my mother doesn''t
freeze her mail-carrying butt off this winter! :)

the diverter vent/baffle/whatever it is in that car that controls how much air from the heater core and evaporator (A/C) gets into the ductwork is either stuck, or the actuator has died (vacuum leak) or the vacuum control valve that is part of the A/C controls is malfuctioning... OR you have a vacuum actuated valve on a heater hose that won''t open to allow the heated water through to actually heat up the heater core.

probably a vacuum line or valve problem. There is a lot to inspect. Good luck.

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Thanks for your help :)

Are both heater hoses that enter the passenger firewall hot to the touch?

I''m not sure, I''ll have to investigate that.

Any luck?

My Sable had no heat when I bought it. The heater core was clogged up with sediment. I tried flushing it, but it was of no use because it was so badly clogged. I had it replaced at a cost of about $470.00

Having similar problems on a 99 Sable.
Just changed the water pump and flushed the coolant out really good. Both hoses are hot to the touch.
No heat at all, but the blower does work.

Could it be the thermostat?
I am also wanting to check the vacuum hoses.
Any idea how to get started?

Thanks
Rod

check the vacuum lines to the vacuum solenoids under the dash that control the positioning of the baffles (the parts that direct cold or warm air to the vents). if you''re getting flow through the heater core, then the problem is in the ducting.

That''s what I figured. Problem is, I know nothing about vacuum solenoids. Any links to diagrams or any kind of directions on how to do this?

Thanks,
Rod