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Re: Heater box - part two

Subject: Re: Heater box - part two
From: Wayne Kube <>
Date: Mon, 23 Dec 1996 20:28:49 -0600
> - the heater doesnt  work at all.
> I do have a spare, used that i picked up but I wondered - before i spend
> all the time putting it in (and this of course AFTER i learn how to get
> the old one out!)
> Is there any way of testing whether the unit is functioning? - I have
> looked briefly at the exploded drawings but short of installation cannot
> really see a sure fire test - any thoughts!!
Mike -
        There's two parts that need to be tested - the blower motor and the
heater core.  Here's how I worked on mine:  Take it apart by removing
the clips and pulling the front of the heater box off.  The blower motor
is attached to the front panel of the box.  If it is a two-speed motor
it will have a dropping resistor mounted to the other part of the box. 
Unmount the resistor or unsolder the wires. You can apply 12 volts to
the motor to make sure it runs properly.  You might open the motor to
clean and lube the bearings and check the brushes.  Or, find a electric
motor rebuild place to check it.  Clean the blades on the squirrel
cage.  Notice how the heater core sits inside.  It should have a foam
rubber seal on the edges so that the air is forced to go through the
core.  Take the core out and clean it - it may have a lot of stuff
clogging the fins.  Clean the inside of the core.  A radiator shop
should be able to boil it out and pressure test it.  I cleaned the water
passages on mine by flowing a lot of water in both directions from a
garden hose.  Then I filled it with vinegar and let it sit for a couple
of hours.  Flowed more water through and watched a lot more stuff come
out.  Repeated until it was clean.  Made my own pressure tester with a
length of hose, air fitting, and pressure guage.  Pumped it up to 20 PSI
and left it overnight - the pressure was still there the next day.  Now
is a good time to clean and paint the box.  When you are satisfied that
it's in good shape, seal the heater core with new foam rubber or
adhesive weather stripping.  You also need to seal where the hose
connectiong go through the front cover.
        Mine works very well - almost too warm if all the air is blowing on my
feet and none through the defroster vents.

Good Luck and Best of the Season to all!
Wayne Kube
Plano, TX       
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