Re: A/C keeps going, and going....

[zm@mhcnet.att.com (Zafer Mehmood [209])]

> Thanks to Steve B. and Eric F. for their thoughts on the
> overactive A/C blower. Unfortunately, I wasn't real clear
> in my initial post - it's running when the CC system is
> *off*, as well as when it's on. And it's definately doing
> it as a result of power applied to the motor (rather than
> forced intake air) because it continues even if the car
> is stationary.
> 

Eric,
	Unless your car is a very early '86, it should have the
black-face-plate Climate Control System with the HI and LO blower
speed control buttons on the lower right-hand corner. If this is
the system you have, here's something you can check:

The A/C control head (that's the one refered to above with the red
LED display and control buttons) has an output to the blower motor
controller. The Bentley manual lists which pin # this is.
This output pin is supposed to put out 3 volts to 5 volts
to vary the speed automatically (3V for LOW, 5V for HIGH obviously)
when the system is on. When the system is off (OFF LED is illuminated),
the output of this pin should be 0, or atleast less than 2 to 3V. In
my experience, the blower will not run with less than 2V on this pin
(at least I couldn't hear it if it did, but my car doesn't have a squeaky
blower motor; not yet:-)

If you are seeing a voltage on this pin when the system is off, then
the control head is probably bad. If you don't see a voltage on this
pin, but the blower still runs, I'd suspect the blower motor control
unit (I believe its in the blower motor housing).

Its quite easy to remove the control head and check the output of
this pin. Bentley shows the procedure (in different chapters though).
If you don't have the Bentley manual, send me email, and I'll tell you
the pin number and procedure to get at it.

Zafer
'87 5000TQ

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Zafer Mehmood				   AT&T Bell Laboratories
zm@mhcnet.att.com			   Murray Hill, NJ