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1996 Fleetwood - Climate Control Fan stays running when the car is shut OFF

Started by cadillacmike68, October 14, 2020, 12:51:08 PM

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cadillacmike68

his is a new one for me.


When I shut the car off a coule days ago, the Climate Control Fan continued to run. I had to disconnect the battery. Re-connecting it made the fan turn back on. PITA, especially since I can't get to the battery when it is in the garage.


Then I thought a bit and decided that pulling the fuse should be a lot easier. That shuts off the fan and I don't have to reset the clock, etc.


OK, I re-started it with the fuse in. The Climate Control seems to respond normally to fan speed and temp dial changes.


However, when I turn it Off with the OFF button on the dash control, the system changes from dash outlets  - remember its still 95 deg here in FL - to the Defroster outlets.


So WTF?? I know that defroster outlets is some sort of fail safe / default operation. Does this mean the dash control has gone out of control?


Further, isn't turning the car OFF supposed to cut power to the HVAC??? I'll check that out in the 3 inch thick service manual. I will also check the car to see if it shuts off the radio when the car is shut off (and the door is opened). If it shuts the radio off, then that would presumably indicate that the ignition switch is operating correctly to shut off all ignition switch dependent circuits. I was under the impression the turning the car OFF would cut power to the HVAC and the blower fan, but apparently not.
Regards,
"Cadillac" Mike

TJ Hopland

At first I was going to say your blower control module had shorted out but removing the fuse would not stop that since its powered by a fusible link.   Blower module must be OK since it can shut off and sometimes works normally.   Must be a control issue of some sort.   

Do you know if the doors are still vacuum operated on this or is it all servo motors.   If there is still some vacuum stuff that opens up possibilities of things just sticking and confusing the computer but if its all servos then I'm not sure where to go next.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

cadillacmike68

TJ - this is my 1996 Fleetwood - no vacuum operated door locks, etc. Power locks from the door work normally with the car OFF and the Trunk will not release in the car is OFF (need to verify this one).

The remote is Inop because the rear deck / trunk mounted remote keyless entry module lost its memory or is bad - but this has been the case since April.

I'll have to dig into the manual - if this symptom is even in there... Otherwise it's time to keep a small needle nose pliers in the glove box.  :P
Regards,
"Cadillac" Mike

cadillacmike68

Supposedly it is in the manual, and this is probably what I need:

ACDelco 15-71971 GM Original Equipment Heating and Air Conditioning Blower Control Module. 

Where is this on the car??
Regards,
"Cadillac" Mike

TJ Hopland

I'm talking about all the air control doors in the ductwork.   Historically on AC equipped cars they were vacuum operated.  A few models got electric motors in the 80's but many stuck to the vacuum well into the 90's.  This being kinda an oddball not super selling model at the end of its run I wonder if maybe it was still vacuum?   The going to defrost is one thing that makes me think vacuum.   On those systems it defaults to that because it take a vacuum power to go to any other mode so if you loose vacuum you get defrost.    Remember a lot of 80's and early 90's cars where they would go to defrost when you went up a hill?   That was why, lack of vacuum from the engine.

I don't think I would suspect the blower module at this point.    Its basically an amplifier that is taking the signal from the main control unit and boosting it to actually do the hard work of controlling the blower,  kinda like a variable electronic relay.   They don't tend to be intermittent and self healing.  They either suffer physical meltdowns of connections and circuit boards from high current draw or the actual electronic device that does the work either shorts out so blower will always be full no matter what you tell it or won't work at all.   Since yours seems to respond to control inputs and removing power to the main controller I'm not suspecting the blower module at this time.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

cadillacmike68

TJ,

OK, yes, it still has vacuum blend / mode doors, but it blows out the dash vents when in AUTO, so that tells me that these items are working.

There is supposed to be something in the manual, but I have to dig it out. On the Cadillacforums site someone posted in reply to my same subject post there about a similar problem with a chev impala SS with Auto temp control and this module came up. He even posted a page out of the chev svc manual. I should be able to dig up the correct section in the Cadillac manual.

Now if I'm able to follow it, well that's another story.
Regards,
"Cadillac" Mike

cadillacmike68

I ordered that module and replaced it. Now it performs properly.

And now I have insufficient cooling. Probably a partially clogged heater core. It's trying to give heat - warms up a bit when set on 90F but nowhere near as hot as it should.
Regards,
"Cadillac" Mike