Here's a breakdown of what's likely happening and how to troubleshoot it:
* Blend Door Actuator: This small motor controls the blend door, which mixes hot and cold air. If the actuator is faulty or its linkage is broken or disconnected, it might not be able to fully open to let hot air in on the high setting. The motor may be working but unable to move the blend door all the way.
* Blend Door Linkage: The actuator operates a linkage system connecting it to the blend door. This linkage can become disconnected, broken, or otherwise obstructed, preventing full movement.
* Vacuum Lines (Less Likely): Older cars sometimes use vacuum lines to control the blend door. A leak or blockage in these lines could also cause issues. However, since you are already having a blower motor issue, a vacuum line problem is less likely, though possible.
Troubleshooting Steps:
1. Listen Carefully: When you select "high" on the fan, do you hear any unusual sounds from the dashboard area? A clicking or grinding noise might indicate a problem with the blend door actuator.
2. Manual Check (Advanced): This requires some disassembly. You will need to access the HVAC system (usually involves removing parts of the dashboard). Once access is granted, you can manually operate the blend door to see if it moves freely and reaches the full "hot" position. This will confirm if the issue is with the actuator or the linkage itself. Note: This is a significant undertaking and requires mechanical aptitude. If you are not comfortable with this, proceed to step 3.
3. Visual Inspection (Easier): While you might not be able to fully inspect the blend door, carefully look for any obvious issues (loose or disconnected linkages) around the area of the HVAC system.
4. Actuator Test (Advanced, potentially requires tools): If you can access the actuator, you might be able to test it with a multimeter to see if it's receiving power and if the motor is functioning correctly.
5. Professional Help: If you are not comfortable doing the above steps, take your car to a qualified mechanic. They have the tools and expertise to diagnose and repair the blend door actuator or linkage. Explaining the symptoms (blower works low/med but not high, only blows cold air) will greatly help them diagnose the problem.
In short, while you fixed the blower motor issue, the lack of hot air on high is a separate problem almost certainly related to the blend door system. The blend door actuator is the most likely culprit.
