Saturn Repair: smoke from heating switch, puff of smoke, little car

Question
Thanks Chris

Here's exactly what happened.  My daughter was driving about a month ago and noticed a funny smell.  She pulled off the road and a tiny puff of smoke came out from where you switch the fan on and off.  She waited awile and drove the car home for us to check.  It did not smell or smoke again the whole way home.  Once at home we were unable to re-create the problem at all.  It never happened again until about a week ago.  She was driving home and had the heat on.  She turned the heat off anf then it started,  The smell and this time more smoke.  But still not a lot.  I decided to bring the car in to see what was going on.  The garage was able to recreate the problem (somehow) and told me it was the heater control unit and that I had to buy the whole unit.  I told him I preferred not to spend $350.00 at this time and he said that I would be safe because the unit would probably burn itself out if anything.  The day after we picked up the car it was worse...more smell...more smoke.  I supect that in order to recreate the problem the mechanic may have pushed the problem over the edge. The first couple of times it was a small amount of smoke for a couple of minutes.  This last time there was more smoke for a longer period of time.  The smoke only comes out around the arm of the switch that turns the fan up and down. Everything else seems to run fine.  The car starts fine.  The only other thing I can't get to work is the lighter and that has been for 2 years.  Thats where we are today.  As I said I really don't want to put alot of money into it because it is old but its a good little car that runs pretty well.  I need to figure it out and see if its worth fixing.  Also I don't want to replace that whole unit if I don't have to.  Thanks again in advance. -------------------------
Followup To
Question -
Hi Chris

Thanks...your answer was very helpful.  I forgot to mention to you that the car starts fine.  There is no problem with that at all.  Would that indicate more that it would be a faulty fan switch rater than a wiring harness proble.  I know you can't say for sure but what do you think?  Also I didn't mention that about two weeks before this happened for the first time I had the brakes done as well as had the serpentine belt replaced.  I also had the front tire rod replaced.  Could any of this contribute to the problem?

Thanks again for your help.

Karen Lua
Answer -
Karen, if the car starts fine then either conditions I described earlier could be the culprit.  A fan switch is nothing more that a series of resistors printed on a circuit board and attached to a lever.  It would only take a little heat to melt those resistors.  So, more than one episode of smoke comming from that fan switch doesn't seem likely.  If you want to pick up a switch, I will walk you through the replacement process.  If the fan still works though, I don't think that is your problem.  You said in your previous message that the car could not be driven.  I was assuming that either the smoke was too bad, or that the car would not run.  At any rate, we need to find something that isn't working (something electrical) so that you can narrow down what system is becomming overloaded.  None of the repairs that you just listed, in my opinion, would have anything to do with your current condition.  I can't say for sure, but that's what I feel.  Anyway, give me more specifics as to what works/doesn't, when the smoke happens, how long it happens and so forth.  We can get to the bottom of this.  
Chris

Answer
Karen,
 Sorry it has taken a while to get back to you.  I've been talking with some of the people that I work with and trying to find a solution to your problem.  Like I said earlier, I've never known a blower switch to short out without blowing a fuse.  Everyone I have talked to has come up with that same answer.  The only thing that I can recommend without having seen your vehicle is a thorough inspection of the wiring behind your HVAC panel.  I'm not going to say that a shorted out switch is impossible, it's just not likely.  If you want to take it apart I will help walk you through the steps. This is just one of those situations that is hard to diagnose over the internet.  If I can be of any more assistance, please let me know.  

Chris