HVAC Problems - "Gear Clicking Noise" Temp Select On Heat & Phantom Vacuum Leak

[Kolya1981]

Having some HVAC problems with my 2003 XLS. I am not sure if they are related or not.

The first problem is I have what sounds like a vacuum leak behind the dash, you can only hear the leak when you push on the gas hard. When this happens and I have the air conditioning on, it will stop blowing out of the A/C vents until I get off the gas. I pulled off the trim for the radio/HVAC panel and also the glove box and could not seem to find the source of the vacuum leak. All of the visible vacuum actuated HVAC motors seemed to function fine too with the engine on.

The second problem is when I turn the Temperature Select knob from cold to hot, I do not get heat, and I hear what sounds like a loud gear clicking/grinding noise about once a second from behind the dash until I turn it back to cold. I am not sure if this problem is related to the first because the temperature select seems to have electrical controls, not vacuum.

Anyone else have similar problems, solutions/suggestions, and do you think the first problem is caused by the phantom vacuum leak or is it a separate problem?

 

[cjones101812]

the clicking is probably the blend door actuator.

the vacuum prob may be the vacuum check valve. not sure but it's a possibity. best bet is to put a vacuum pump on the system and pump it down, check for leaks. if no leaks found, remove pump and see if check valve is good (will hold vacuum if good)