90astro/heater selector problems

[shroom59]

HI, the fan blows on all speeds, but you dont get anything but defrost, no floor, or heat at you, those selectors dont seem to work, also after rebuilding the engine, it takes a really long time to get heat, the guy who rebuilt it said he uses a low temp thermostat, so that the engine get fluid right away, perhaps i should go back to the oem recommended one, the engine is a 4.3, bored out .40 thousands over. thanks for your help

oh and i just replace the master powerwindo switch on the drivers side, its windows are fine but the passenger side doesnt work, its winter and the window is down 2 inches, perhaps i should get another master switch, the lady was putting it down while i was hitting the master switch to put it up, perhaps weshorted something out, anyway of jumping that side just to get it up??. I noticed, two blue,brown,tan, and black wires to the connector.

[8490astro1]

Hi, it is probably a loose hose. If yours is like mine, remember those annoying things that looked like wires when you removed the interior engine doghouse? They usually get in the way. If they are missing, broken, or damaged, your flapper valves will not change position, and it will be stuck in defrost mode.

If those colored hoses are all ok, the problem is with the vacuum hoses coming from the engine. On a 1990 model, which is probably the same as yours, the hose which generates vacuum for the flapper valves is on the right (passenger side when you are inside the vehicle) near the doghouse attachment clip/bracket. It will be in the upper corner, somewhere around the alternator. Usually, they rot out and come loose, or are pulled off when the cover is being put on. Usually, the hose will run down to a ball shaped vaccuum storage canister, with a "t". The other end is a hard plastic hose, which runs up into the interior. If you connect this directly to vacuum, it should work. You must remove the air filter/intake.

As far as the window switch goes, I believe there may be a relay for that somewhere, maybe near the fuse panel? First, try to wiggle the passenger switch a little. Then, on the drivers side passenger switch, push harder in the center of the switch, then up. See if the combination of this works. The switches are in a loop circuit, and the "center" position has an on mode - you can't short it out by the up-down thing. Usually, what happens is the center position contacts in the switch do not make good contact, as a result of a worn out piece of plastic in the center of the rocker. If you wish to replace these switches, buy the switches for a 1986 Buick Century or oldsmobile from a junkyard. Please verify the pinout when you go the the junkyard, as it has been a long time since I have done this.