Ac/Heater/Vent problem

[xs04298]

Hello, I have a 1989 240sx hatch with about 230k miles on it. When i bought it i knew the air didnt work, but i just recently discovered the heat isnt working correctly either, the blower works, it pushes air, but only through the defroster vent, doesnt matter what button i push it always comes out through the defroster vent, i took out the ac unit and made sure all the wires were hooked up and they were, the buttons work and click ect, i'm really not sure where to start, looked through chiltons and that was no help as usual. Anyone have any idears?

Thanks

[180fan]

did you leave the plastic casing that was over the AC core in the car?

[xs04298]

Not to sure I understand what you are askin...I havnt changed out anything in the AC system, its all untouched, My gut feeling is that its somthing in the control unit itself, because if i turned off the defroster it should at least turn that off even if the other vents were blocked i would think, but it doesnt even do that, and none of the little buttons are lit up at all, and when i hit the a/c button i certainly dont hear the compressor kick on, and it has freon, so i'm just very confused haha

[180fan]

Check the plugs on the back of the control unit. Check fuses as well.

[NISTECH]

It sounds like you control unit has a bad contact internally.

[tonynalli]

i have a similar problem with my 92 coupe, sometimes it wont go into defrost mode and now it all works but there is a litte air coming out of the defrost vent. havnt taken teh system because the bugs at my place are horrible and its a little hot but i will do it soon

[xs04298]

Ya'll were spot on, was the control unit, took it apart and the circuit board had a lot of burn marks on it, just bought a new one on ebay hope it fixes er

[NISTECH]

dont confuse excessive flux with burn marks.

[xs04298]

Well, hvac unit didnt fix my vent problem (no prob, was cheap and needed a new one anyway visualy). Is there a fuse for this system? my fuse box is worn and none of them are labled anymore...

[NISTECH]

just use a test light and probe the back of all the fuses where the slots are. With the key on. the light should illuminate every time you hit power. if you have power on one side of the fuse but dont on the other the fuse is blown replace it.

[xs04298]

Went through the fuses, nothing bad (there is only the one outer fuse box in s13's right?)

i'm just stumped, must be somthing wrong with the vent it self that its not switching them over, although the lights on the switches still arnt lit up (i only assume they should be though)

[NISTECH]

there is the fuse box in the kick panel by the drivers foot and the one under the hood.

The lights in the buttons should only light up when that button is pushed. If it doesnt light up you are lacking a power or ground to the unit.

[xs04298]

You are a godsend! it wasnt a bad fuse, it was just plain missing, the crazy cat that owned it before used it to power his indiglow lights and didnt replace it, all fixed now Thank you very much!!

[NISTECH]

Thank you for posting back. Too many threads dont get the fix posted. So it leaves it to wonder weather it was fixed by the material posted or if it was found to be something else entirely.