Mike Jones-

[Herold Berthy]

Mike - I was directed to attention this one to you.

Dont know if this is the proper forum, but -

My low-milesage Brougham has a second(?) fan up under the
dash which suddenly decided to keep on running, after the
engine (key) was shut off and even after the door was
opened - even after the Climate Control was switched to
off - and it showed off. Now I have to take the
pos terminal off the battery to keep from runing it down.

Anybody have this experience? Im not much of a mechanic,
but I do have common sense (argueable)- Ive tried both
fuses which seem to be labeled HVAC, to no avail.
Help!

Herold Berthy, Morgantown, WV (member - cant remember
number and my mags are elsewhere)  

[Mike #19861]

 Herold,

 Ill do my best to help. First of all, what year is the car? If it is an 80s Brougham, chances are its a failed power module. You can find this under the hood located to the rt rr and bolted into the HVAC box. It has a large pinkish/orange wire coming out of it, with a smaller connector with about 6 wires coming out of it. There is a procedure to diagnose it correctly, but if you can borrow a known good module and plug it in, you can quickly determine if it a defective module or not.

  Mike

[Herold Berthy]

Sorry - its a 1994 Brougham - it sounds like a second
fan for the defrost - it just never shuts off.  I had this
trouble with my air pump a few months ago (I know theres
no relationship) when I took a 400# friend for a short
trip in the back seat and apparently pushed the sensor
past its limits.  My mechanic (parts-changer, actually)
just let the air out of it, and it went back to normal.

I tried both the fuses that indicate HVAC, and the fan
continued to run.  As a real novice, I didnt see any
other labels that seemed to apply to the system.

Any help you can give me will be GREATLY appreciated!

Herold

[Mike #19861]

 Interesting dilemma. Ill research it a bit and let you know what I find.

 But Im confused by your description of the problem. You can actually hear a fan running in the dash that never shuts down. Is this at low speed? How would a passenger in the back seat affect it?

  Mike

[Herold Berthy]

It came on unexpectedly one Sunday - I had been driving for
a while and the HVAC system had modulated down to a low
speed fan (I always leave it on auto).  Suddenly this
other fan noise came up, (as in maybe a seperate defroster
fan?)  I didnt think anything much about this, until I
stopped at a restaurant, shut off the ignition and got
out of the car - fan still running.  I ate (more quickly than
normal), took my passenger home, and returned home - no
change.  I then tried both fuses labeled HVAC in the
owners manual - no change.  So I simply disconnected the
positive lead to the battery, and havent used the car
since (I have others, like most of us).  Im still working
my normal 16-hour days (Im 70, but whos counting?), so
I really havent had a lot of time to research it, but
the Allante season is about to end, so I really would
like to return to the Brougham for the winter.  Any
ideas at all?  Anything you think I should try?  Im
not the greatest mechanic in the world, but I can follow
simply directions.  Please?

Herold

[Herold Berthy]

Since in all that, I didnt really answer your
questions---------

I dont see any difference whether I have a back
seat passenger or not (I did have the day that it
started, but I continue to have it when driving
alone).

Driving speed seems to have no effect on it.

Im going to try some more stuff over the holiday
weekend (saving gas - not going anywhere!).

Thanks

Herold

[Mike #19861]

 Herold,

 Just a thought. I was working on a friends 95 Caprice yesterday and while checking the ALDL for codes, the secondary cooling fan came on at low speed. Is it possible that this is what you are hearing?

 For the life of me I cant envision having a second heater fan in the dash.

  Mike

[Herold Berthy 11014]

I dunno - Ill hook up the battery tomorrow and
give it a shot.  Thanks!

Herold

[Herold Berthy 11014]

Finally found time to mess with it again.  The reason I kept
thinking there were two fans was that when I turned the system
off, the fan noise came from a different direction (of course it
did, duh, all the little vacuum directors changed their position,closed,whatever).  The good news is, I finally figured
out that there is a third fuse (25a) which seems to shut down the whole system, so I can at least park the car without unhooking the battery cables.

Now   -    is it possible that this system is hooked up with a constant hot with the circuit being completed by various grounding devices?  That would explain why turning off the ignition did nothing to stop the fan.  Whaddaya think?

[Mike #19861]

 Removing that fuse is a start to finding what is really draining the system. The drain will be on that circuit.

 There are many modules in these cars that work many functions in the cars, some can remain on and drain the battery. Usually, after a few minutes of inactivity, they will go to sleep and the total drain on the system will be in the 50 -75 mA area, which should allow your car to remain inactive on a fully charged battery for a few weeks and still start when you need it.

 By removing that fuse and finding that the draw stops, you have narrowed it down to the circuit(s) fed by the fuse. The next step is to investigate the circuit and any potential draws that can kill your battery. This is where the shop manual comes in handy. All the circuits are laid out in an easy to follow fashion, with charts for locating specific components. With some diligence and a logical approach, you should be able to locat the scource of the drain.

 But, for the time being, removing the fuse when you park the car will ensure you have a full battery when you go to use the car again. No harm done there.

 Mike

[Herold Berthy 11014]

Thanks again - ordering the shop manual from
Helms as we speak (a bit expensive, though).
Oh, well; I expect the car to last me the
rest of my life anyway, so its probably a
good investment.  Thanks again.
Herold

[Mike #19861]

 Youre welcome.

 Helms is a great scource for shop manuals, they print them for GM. But like you say, they are expensive.

 An alternative is E-bay or one of the literature houses. They offer an economical scource for the same manual. It may be a bit used, but you are goung to use it anyway.

  Mike