Help Me Diagnose Heater Issue (94 Ls400)

[Och]

So I've had this issue with my heater ever since I got the car, but I never bothered to figure it out. Here's the deal.

First of all, I usually set my temperature to 72 degrees in the summer and in the winter and I set my vents to blow from the dash and the floor. In the summer time, there are no issues, the AC works nicely and 72 degree keeps the cabin comfortable and not too cold. Of course, if its really hot outside, I just set it to max cold.

Now, in the winter its a different story. When I set it to 72 and the cabin is cold, both the floor and dashboard vents blow warm air. However, as the cabin warms up and becomes comfortable, the dashboard vent starts blowing cooler and cooler air, while the floor vent keeps blowing warm air. Once the cool and warm air from these vents mix, the overall temperature in the cabin is nice and comfortable, but the cool air blowing directly at me from the dash vents does cause some discomfort. So then what I do is set the temperature to 75, which makes the floor vent blow even warmer air and dash air also warms up, however once the cabin reaches warmer overall temperature, the dash vent blows cool air again but floor vent keeps blowing warmer air. If I raise the temp to about 80, the air that blows out of dashboard vent never drops to be uncomfortable, but the problem is, floor vent is blowing air that is way too hot.

My understanding is that there is a cabin temperature sensor underneath the steering wheel, that lowers the temperature of the dashboard vent air as the overall temperature of the cabin goes up. But why does it lower it so much, and how come the floor vent isn't being affected?

[landar]

Mine does something similar but it never seemed a problem to me. Usually, in the winter months, the floor vents(mostly) blow warm air.

Summer is "in my face" with A/C, which is fine with me.

In the winter, as it warms up (the controls are on "auto"), it might begin blowing both floor and front. You can manually override the air flow(mode) and direct out the

floor only if you prefer. If bothered by the front air, you could just re-direct the vents or close them(partially/fully) off.

[eatingupblacktop]

So I've had this issue with my heater ever since I got the car, but I never bothered to figure it out. Here's the deal.

First of all, I usually set my temperature to 72 degrees in the summer and in the winter and I set my vents to blow from the dash and the floor. In the summer time, there are no issues, the AC works nicely and 72 degree keeps the cabin comfortable and not too cold. Of course, if its really hot outside, I just set it to max cold.

Now, in the winter its a different story. When I set it to 72 and the cabin is cold, both the floor and dashboard vents blow warm air. However, as the cabin warms up and becomes comfortable, the dashboard vent starts blowing cooler and cooler air, while the floor vent keeps blowing warm air. Once the cool and warm air from these vents mix, the overall temperature in the cabin is nice and comfortable, but the cool air blowing directly at me from the dash vents does cause some discomfort. So then what I do is set the temperature to 75, which makes the floor vent blow even warmer air and dash air also warms up, however once the cabin reaches warmer overall temperature, the dash vent blows cool air again but floor vent keeps blowing warmer air. If I raise the temp to about 80, the air that blows out of dashboard vent never drops to be uncomfortable, but the problem is, floor vent is blowing air that is way too hot.

My understanding is that there is a cabin temperature sensor underneath the steering wheel, that lowers the temperature of the dashboard vent air as the overall temperature of the cabin goes up. But why does it lower it so much, and how come the floor vent isn't being affected?

I agree with Landar. There's nothing wrong with your system. I think they're designed to function as they do because most people drive their cars in the winter wearing their coats, scarves and gloves for the duration of their trip. Unless it's a long one. Once the cabin warms up to the specified temp, the dash vents cool down a few degrees in comparison to the floor vents to prevent the driver & pass from overheating. The feet get warmer air because the footwell area gets cooler quicker and you have to keep them tootsies frostfree so you can feel the pedals. In the summer the reverse happens. Hot air rises, and add the sun shinning through the windows, so the dash vents blow a bit cooler. I believe the owners manual explains some of this. There are any number of options available to come up with a combination that works for you. Just play with the controls for a bit.