This is one of those problems that could be a couple of things. A lot of people replace the blower motor resistor and it fixes that problem. I have done this and it is moderately easy with a $40 part from the dealer. However, this did not fix my problem.
Then there are other people, like myself, who had to replace the ignition switch harness to fix the problem. The primary difference in the symptoms I saw with this problem versus others was that my headlights would go off when I selected a "bad" fan setting. Also, some of the lights near the fan now would freak out, like the AC light and the defrost light. This fix is more in depth and requires removing a lot more parts around the steering column and under dash. The part is ~$100 from dealer or about $60 online. Good luck.
Blower motor resistor
And here is how to change this little bastard
. Remove the underdash panel on the pass. side. There are three push tabs that hold it in. At least on a 97 GTP. Ok you have the panel off. Set that somewhere you will not foget it.
With your head in the floor look torward the firewall. The blower resistor is mounted in the bottom of the HVAC ducting. Unplug that harness that attatches to it and move it out of the way. Now take a 5.5 mm socket and remove the blower motor. Once that is down and the plug is disconnected, set that aside. If you have bought the blower resistor, then you will know kinda what to look for. You can see two of the three 5.5mm bolts that you need to remove. Remove the easy one. That is the closest one to you. Somewhere in here you will need to be on your back, head into the center console, and cussing cause you're not left handed. Next unbolt the remaining bolt that you can see. It may not unbolt all of the way because the sound deadener is in the way. Here is the choice. Use a knife and cut it, or just unbolt it was far as you can. For the last bolt, it is hidden behind a plug connector. You cannot get to that one without cutting the sound deadener or breaking the blower resistor. I chose to break it cause did not work anyway. I got it out. Not too bad. To make it easier to get the new one in, loosen that last offending screw a turn or so. I put a light coat of silicone on the new piece to seal it well since I would not be able to turn that back screw.
Installation is the reverse. Before you button it all back up, make sure the blower works.
Also here is a post from another person on how to replace the Ignition switch harness
Ignition switch harness
Quote:
I have a '97 GT that I bought new, so I've had my car on the road longer
than most of those in this group. That being the case, one can reasonably
expect equipment failure to show up sooner on my GP than on newer models.
One interesting failure is something called the "fan ignition switch." That
switch is a thick cluster of heavy and lesser wires, about 1.5 feet long,
with robust termination blocks on each end. One end also has geared,
mechanical components. This part installs under the dash on the drivers
side and up into the steering column.
You need to replace it when your A/C fan begins to operate intermittently.
For example, if you are driving and the fan simply stops, then restarts
while on any speed setting 1-4 (not on speed setting five setting until some
weeks later ,) your switch is failing. The problem will gradually become
worse, with the outage taking longer to recover, until you achieve total
failure.
There are actualy two parts that can cause this problem, and the second part
is called the resistor pack. That part connects directly to the blower
housing under the dash on the passenger side, and is about 24 bucks new from
GM. My fully functional pack was slightly burned on the circuit board, so I
replaced it.
The fan ignition switch was easy to replace, but it is awkward to install.
You will need typical small hand tools, plus an 8-inch or longer socket
extension. a torx male socket (T11, I think) and two torx female sockets
(T11 and T10.) I didn't know that until I had my steering column torn down,
and had to drive around the city with a skeletal column, wires dangling and
tools in the floorboard. No one sells female torx wrenches that small, so
you will have to buy two small standard wrenches. (Your 1/8th inch drive
sockets are way too big to fit the space you will have to work with.)
Sears has a perfect solution. Buy the 5/32nd and 1/8th size wrenches on the
2.5 inch steel stems. They look like small screwdrivers with the socket
permanently mounted at the end of a thin, steel stem. You will need the
small stem because you won't be able to remove the cowl above the steering
column, and its in the way.
The physical key slot on the primary ingnition switch is too big for the
upper steering column cowl to slide over, so you will have to raise the
plastic cowl as far as possible to access the two very, very small torx
screws holding the fan switch in place. The cowl will be stressed, so be
careful.
Also, you will have to cut and splice two wires due to being unable to
remove the upper steering column cowl. There is some magic part snapped
into a slot on the top of the column that you will not be able to reach,
which will have to be left there. Cut the two wires coming off it and
splice them to the two matching wires coming off your new part. There is a
small, odd shaped white plastic box attached to one end the two wires.
Nothing comes out of the little box, and there are no metal contacts on the
surface of it. Apparently, there is something inside the box that sends
some kind of signal/magnetism/charge through its housing to a receiver in
the steering column. Or not. Who knows?
The wires are very plainly marked, they match the new ones and there are
only two. You can't screw it up unless you fail to insulate your splices.
If you don't unsulate them well, then you can expect some really fun
problems later, and maybe even some fireworks in your lap as you drive down
the highway, impressing your woman with your technical prowess 
That job takes about 1.5 hours, and the part is 56 bucks from Grand. GM
wants 98 dollars for it, and a shop will charge you around 300 dollars to do
it
|
Just to add to his directions, to get the top cover off, put the key in the ignition and turn it to START (disconnect the battery first!), and then leave it. Push a small allen wrench in the hole above the ignition switch, and you can pull the whole thing out. Then you can remove the small white thing, which has a button on it, and controls the key alarm that tells you when you've left your keys in the ignition. The tip about the Sears tools is definitely a life saver. The 2 driver's you need are:
SEARS
Craftsman Professional 1/8 x 2 1/2 41865
&
Craftsman Professional 5/32 x 2 1/2 41866
They're $2.99 each
Sorry for making this so long,but im sure if others use the search it will come in very handy
~Larry~