Heat Blowing under Dash

Something similar happen last year with my 1986 coupe. The temperature regular was stuck in the on position. In my car it seems to be an on/off system and the little knob simply changes how long it stays open. Sort of like intermittent wipers. Undriveable! These things have blast furnace heaters.

I did not want to bother with fixing it for Summer and simply found the hot hose in the front trunk then incrementally and very easily crimped it down with needle nose plyers to stop the flow. Last Fall figured to let some small amount of hot water through for Winter and discovered the regulator had begun to work again. Still is.

 

I would think in Texas that you would have enough heat as it is.

 

Texas and Oklahoma in August! Back in the early 1970's I was driving from San Diego to DC for a Park Service job and crossed the Oklahoma Pan-Handle at noon. The car did not have A/C and it was so hot I had to close the window to protect me from wind dehydration. Finally stopped for gas, found some shade trees, and lay down to cool down.

When I was cooled down I got up to leave and noticed the temps had cooled down to 100F. HEAT! That was very dry heat and is an entirely different thing from humid heat. In that same decade I was working in Summer in Tallahassee Florida when it was 105F at mid day. Simply walking from the motel room to the car started to soak my shirt.

Now I live in the North Georgia Mountains where Floridians come for Summer and where I escaped Chicago Winters. The Floridians wonder how it is I can take the Winters!. After living 13 god forsaken years in Chicago I can authoritatively state the North Georgia Mountains do not have Winter.

 

Your heater valve is stuck open

there are quite a few threads about it

its located in the right side passenger footwell

simple check is to make sure the wire connections are properly fitted

unplug then clean and plug again

 

Before going after the hot water valve itself, it is much more likely that you have an electrical fault. When the key is "on", but the AC/heater is "off", the electrical system supplies +12V to the hot water valve to always it closed. The first thing to check is if the passenger cabin blower fan motor is working or not (the same +12V to run the cabin blower fan is also used to hold the hot water valve closed when no heat is needed/requested) -- i.e., turn the AC/heater "on", and set the cabin blower to full speed:

If the cabin blower isn't working = most likely blown fuse or frazzled white connector connection at the fuse-relay panel.

If the cabin blower does work (but hot air always comes out) = then that warrants making some electrical measurements at the hot water valve connector itself (but an actually 'bad" hot water valve is the lowest on the suspect list IMO).