98 Chevy heater controls location.

[gpet6669]

I am having problems with my heater not changing locations (ie; defroster, dash and floor), it basically stays on the defroster but it also moves from dash and floor. In short, the defroster stays on, but the dash and floor shut off and turn on when they are sapposed to.

I have no idea where the controls are for the directional air flow.

If one of you guys (or girls!) could get me in the right direction so that I can figure out if it needs to have the solinoid replaced or just get it unstuck.

Thanks, Gary

[NITROUS]

All of the controls are in the evaporator box under the glove box. You might have pull the box if the damper (mode door positioner) is broken.

[gpet6669]

Do you think that would be what it is?

You said that it is behind the glovebox? The reason that I ask is because I had the dash pulled back to get to the passenger airbag. So I may have messed it up.

[GasGuzzler]

The vacuum actuator for mode is on the LH side of center on a GMT400, right NITROUS? The temp and recirc actuators are electric but I'm pretty sure the mode actuator(s) are vacuum. Make sure the vacuum source from the engine is OK too.

[NITROUS]

The vacuum actuator for mode is on the LH side of center on a GMT400, right NITROUS? The temp and recirc actuators are electric but I'm pretty sure the mode actuator(s) are vacuum. Make sure the vacuum source from the engine is OK too.

Correct Gas Guzzler.....

I would start looking at the wiring to make sure something hasn't been pulled off. Some of the connectors are hard to see so look closely.

[gpet6669]

I tore into it last night and found that the butterfly that shuts off the defroster was out of its position so it was just flopping around in the housing. I also lubed it up while I was in there.

On another note, I am wondering if you guys have figured out a way to fix the fan control switch's 4th position. It is the position right before high. (medium-high) I have replaced the switch twice and it works for about a month and then it quits. The rest of the positions work, but only that one quits. I have broke down the switch and the terminal bends everytime. I just put a piece of plastic under the terminal to see if that would help to keep it from bending, but that didn't work. So does anybody know how to fix it permenantly so I can use that speed on the fan?

Would soldering the terminal work? Or do I have to do something else?

[GasGuzzler]

These trucks are good for burning up that connector. You can get a new pigtail at the dealer if the terminals are fried or the plastic is melted or brittle.

The resistor for the speeds is behind the glove box on top of the AC case. They have trouble some times too. Also make sure the blower motor ground is good.

[gpet6669]

Like I said it was just the flapper that shuts off the air to the defroster.

I checked all of the solonoids and they were working good. Just that one vent block thing!

I ended up following all of the piping from the passenger side of under the dash.

[NITROUS]

I've found that the motor will cause your problem with blower speed also. Check the motor connector (I believe the red wire) and see if it's started melting or gets hot when running. You can try tapping the motor when the switch is in the 4th position and if it starts, replace the motor. I hope you cleaned the evaporator real good when you opened the box up because you'll lose air flow from all of the outside trash that gets in it.

[gpet6669]

What are you talking about being cleaned, I went in from the center by the floorboard inside the cab. I didn't see anything that would need to be cleaned.

Please elaborate!