Rusty84

Hello I have a 1990 LS 400 I'm having trouble getting my control panel to work its like my heat is stuck on even if I unplug the panel the heat still blows out I have tired three different panel as soon as I connect them the heat pops on I'm not able to control nothing on the panel the lights just blink green some one please help it's starting to get HOT in Texas

oldskewel

iTrader: (1)

Does the fan blow hot air, or does hot air come out even though the fan is off?

dicer

Does the heat control valve work? The one above the right hand valve cover.

Rusty84

I unplug the panel but hot air still comes out the vent it was blowing out cold air before I change my thermostat nothing on all three panels work only the switch to control to blow out the top are bottom that's it pls help

oldskewel

iTrader: (1)

Is the hot air being blown out by the fan, or is it coming out while the fan is not blowing? (2nd try)

Rusty84

It's coming out while it's off it's heat blowing while I'm driving the car it's bad in day time around 4-7pm

oldskewel

iTrader: (1)

OK, so that is a "feature" of the HVAC systems in these cars. When the HVAC control is on, and you dial in a temperature, it will adjust the heater valve accordingly to make it hot. For example, it may set the heater valve wide open so the heater core gets hot.

Then if you turn the HVAC system off (or unplug the whole thing like you did), the heater valve is still in the same full-hot position if that's where it happened to be at the time you turned HVAC power off. When you then drive around, the air pressure from driving will force (even without the fan blowing) air through the heater core and then through the vents. So you'll be getting hot air out even though you might think the HVAC should be completely off.

This actually is a nice feature, allowing you to get some heat or fresh air without having the fan running - nice and quiet.

If your HVAC control is dead and you're just looking to stop the heat while you get it fixed, I recommend you find the heater valve that dicer referred to. Maybe you can manually change it from full hot to full cold.

Rusty84

What about the blend door could that be a issue

billydpowe

iTrader: (1)

why are you worried about the blend door, did you get in there and damage it?? if not, go do what oldS said and manually close the valve and cut off the water...

Rusty84

I'm just trying to get my a/c working the compressor comes on but no cool air

Rusty84

I close the heater value thanks it feel much better now

billydpowe

iTrader: (1)

you need to check craigslist and find a parts car with a good control unit and fix it...

Rusty84

I have bought three already they all do the samething so I'm thinking it's a short are electrical

dicer

What you need to do is the diagnostic for the climate control system, its kind of involved and I think someone posted a how to on it some place. I think your problem is the servo motor that operates the heat control valve, not the actual climate control unit. The self test should isolate the problem for you. And then its not so hit and miss.

Rusty84

OK I'm looking into it now good looking