Reader Question: I have a 1996 Pontiac Transport Van. For the past couple of months when switching heater modes (defrost to floor to bi-level etc) there can be along delay before the transition happens. I can take up to 15 minutes at times.
This started before the cold weather hit but was not frequent. Not to really confuse things but about the same time as this problem started I noticed that my cruise control required me to be going a lot faster than usual before it would work. Could this indicate a vacuum leak affecting both?
Now the problem has developed into a blower that sometimes comes on and sometimes not. Like the problem above, if I leave it in the running position I can be driving or stopped when it will just start running on its own. When working the heating is fine as I did not notice a loss of heat.
Both of these problems are getting more frequent.
I do not know if all these problems are related or not. I would look and listen for a vacuum leak under the hood like in a rubber vacuum hose that has cracked and come loose or a plastic connector that is broken. Lack of enough vacuum could be related to the first problem you mentioned.
There could also be a vacuum leak inside the dash as well, so listen for a hissing noise inside the cab with the engine running.
There is an electric blend door motor inside the dash that could be going out on you, which would cause the slowdown in selection.
The last blower issue you mentioned kind of sounds like a weak or bad blower motor to me. Next time the blower motor quits, see if you can lightly bang on the outside the blower motor itself with a rubber hammer or a block of wood to jump-start it again. Do this with the engine running and the blower selector in the ON position of course.
You might be able to get to the blower motor from under the hood or under the dash on the passenger side.