2 questions. What yr is it? It is not normal for the compressor to be on in the "vent or floor settings" so the questions is, when in these non a/c positions, does the blower fan work the same as in the a/c positions?
It's a 2000.
Blower works normally. Just the compressor is on.
Thanks for your help.
OK. The common link is the mode switch (right switch on the panel) & the 3 wire connector on the back. Make sure the 2 green wires are not touching or connected somehow. If not, the switch may be bad. The smaller gauge green wire (top position) is the compressor wire. The switch is supposed to ground that wire when in positions requiring the compressor to engage (a/c & defrost). When grounded it closes the compressor relay. In the other positions including off that wire should not be grounded. The larger gauge green wire (middle position) is for the blower fan. The switch grounds that wire in all switch positions except off. Both of those get grounded through the bottom black wire. Since it is turning off when the switch is off I would guess the switch is OK & the green wires are connected. Sometimes the connector gets melted & the wire can touch. Other times the connector melts & gets removed & the 3 wires are connected separately to the switch & if you reverse the 2 green ones (I’ve seen it a few times on the forums) then the compressor will come on in any position like you have but the blower fan will only work in the a/c & defrost positions. That’s why I asked about the fan.
I will have to check the wires. I'm pretty sure the wires aren't touching. I'll have to check it to make sure. It almost seems if I twist the selector switch a few times before letting it stay on whatever I want (ie floor/vent heat) the compressor won't kick on.
That makes me think the switch is bad. If the wires aren't touching there is almost no chance it is anything but the switch. The top green wire must be getting grounded when it shouldn't. If you have a meter you can test the continuity between the top & bottom terminals. It only have continuity when in the a/c & defrost positions.
Since it is apparently switching positions & directing the air where it should this probably is it but when you take the knob off make sure it is not cracked where it goes onto the switch shaft & that it is turning the switch to the correct positions as you turn it.