All hot or all cold - heating/cooling

[kawter]

SIAP bit after searches I have found several
Threads about no heat or no cold or bad “auto” settings but can’t seem to find this one.

The situation for my ‘00 LX470 as of about 3 months ago was that the temp of the air coming out of the vents stayed 100% “cold” (or in-heated) until it hit 85° on the adjustment dial (not auto). (Actually I could feel a TINY difference at 84° but very negligible)

Then all of a sudden I have the exact opposite, On cold, the air seems to be “untouched” or “cold” then just one click it turns 100% HOT.

Leads me to believe the blend for is acting in a binary manner where it only knows open or closed and nowhere in between - but not sure if that’s due to electrical or mechanical or what in the world

Anyone have this issue and fix?

 

[kawter]

*un-heated*

 

[89BIGBLUE]

Did you check the temp sensor plumbing behind the lower dash, almost directly below the ignition?
If it can tell what the interior temp is, it might not be able to send you the temp you’re asking for.

 

[Dziobak]

@kawter - I dropped your post into a GPT I've been playing around with that's trained on the FSM/Diagnostic handbooks for LCs. Hope this is helpful!

Thanks for the details about your 2000 LX470. Based on your description, it sounds like you are experiencing an issue with the blend door actuator. The blend door actuator controls the mix of hot and cold air to achieve the desired temperature. When it's not functioning correctly, it can cause the symptoms you described where the temperature suddenly shifts from cold to hot without any gradation.​

Here are a few steps you can follow to diagnose and potentially fix the issue:

### Diagnosing the Blend Door Actuator

1. **Check for Error Codes:**
- If you have an OBD-II scanner, check for any HVAC-related error codes that might indicate a problem with the blend door actuator or its related components.

2. **Listen for Noise:**
- Turn the temperature dial slowly from cold to hot and listen for any unusual noises like clicking or knocking. These noises can indicate a failing blend door actuator.

3. **Inspect the Blend Door Actuator:**
- The blend door actuator is typically located behind the dashboard, near the HVAC unit. You may need to remove some dashboard panels to access it.
- Look for signs of damage or wear on the actuator.

### Replacing the Blend Door Actuator

If you determine that the blend door actuator is the issue, you may need to replace it. Here are the steps:

1. **Remove Dashboard Panels:**
- Carefully remove the necessary dashboard panels to access the blend door actuator. Refer to your repair manual for detailed instructions specific to your vehicle model.

2. **Disconnect the Actuator:**
- Disconnect the electrical connector from the blend door actuator.
- Remove the screws or bolts holding the actuator in place.

3. **Install the New Actuator:**
- Install the new blend door actuator in the reverse order of removal.
- Reconnect the electrical connector and secure the actuator with screws or bolts.

4. **Test the System:**
- Before reassembling the dashboard panels, test the HVAC system to ensure the new actuator is functioning correctly.

### Resources and Diagrams

Here are some direct links to get you started:

- **IH8MUD Forum Search for Blend Door Actuator Issues:**

- **LC100E Manuals:** for LC100E HVAC System Manua

For example, you can find relevant information on the HVAC system including the blend door actuator in the LC100E manual linked above. Look specifically at sections related to "Heating, Ventilation and Air Conditioning" or similar terms.

If you encounter any difficulties navigating these resources or need specific pages from the manual, please let me know, and I can help you find exactly what you need.