2002 Sonata Climate Control

My sonata has the automatic climate control without knobs and without the
cabin filter. The fan will only turn on if you select the highest speed. All
the other functions seem to work like normal, meaning no matter what the fan
speed is set at I can change modes for the vent positions, temp control, AC
on or off, ambient outside temp. Obviously the Auto mode doesn't work to
control the fan either, but it does change the vents and the L.E.D. fan
speed indicator changes as I change the temperature settings. Does this mean
that the climate control is bad or is there something else wrong such as
sensor, wiring ect...

Thanks,
Dave

 

The control commands high speed by grounding a relay. Other speeds are
commanded by duty cycling a power transistor. There are several
possibilities, but I'll give you ten to one odds the problem is the power
transistor.

 

And that looks to be located somewhere near the blower according to the
schematic. Thanks for the tip!

 

I can't recall whether it's behind the center of the dash or in the blower
box where the resistor would normally be. The schematics have links at
the bottom of the page. One of these is for a component location index.
Follow a couple links, and voila, you've got a nice picture of whatever
dealie you're looking for.

 

Unfortunitly the PT isn't the issue or at least not all of it. Installing a
new one didn't resolve the problem. Do you have any other ideas?

 

It's possible the issue is in the wiring or the climate control itself.
Neither of these is a high frequency failure and the climate control head
is rather expensive. I'd therefore recommend spending the time to check
the wiring thoroughly.

Unplug the power transistor. Check to see if you have voltage present in
the Black/Orange wire. It may be somewhat reduced from 12V (depending on
your testing device) because it goes through the blower windings prior to
arriving at the power transistor.

Check for ground in the black wire. You already know the connection at
the ground location is good because the fan works on high speed and this
uses the same ground lug. Your voltage between the black/orange wire and
this wire should be very close to the same thing you got in the above
test.

Check for continuity in the Green/Black wire. You'll need to remove and
unplug the control head and check from one end to the other. Also check
to make sure this wire isn't shorted to ground (i.e. check the resistance
between the wire and a verified ground and verify it's an open circuit).

If these three wiring tests check out and the power transistor is known to
be good, then you have a defective control head.