Heater/AC Zone Problem 1998 Z34
 

I'm having a problem with air blowing only through the defrost vent and the floor. I can't get air to blow out of the vents on the dash.

I've looked under the dash and the vacuum hoses and connections all look good, as far I can see. I can't trace them all the way to each vent. The electronic connectors plugging into the HVAC unit and what is I guess the "UIM" (?) are secure. I do hear a clicking noise which sounds like it's coming from under the hood when I change the switch position?

It started doing this in the winter; they were working fine before. When I first got this car about a year and a half ago I could hear something in the duct work, like a leaf or a piece of trash. Today I took the vent cover on top of the dash off for the first time. Some of the clips that keep it in place were broken before I tried to open it and I found two of them inside but no trash or leaves. I mention this in case a piece of something could be blocking a vacuum hose. I don't have any idea.

Right now it is blowing air through the defrost vent and the floor at the same time regardless of what position the switch is in.

Does anyone else have any ideas? Here is a link to a brief thread where this was discussed before - https://montecarloforum.com/forum/mo...peoblem-33565/

Thanks.

Problem would be the blend door actuator, the changing of zones isn't done by vacuum, its done by a set of flaps if i recall.

Hey, thank you. Now I'm off to find what that is and where it's at.

not true, they are controlled by vacuum.


there is a plastic vacuum line that runs on the passenger side near the battery. if that had broken over the winter, you will no longer have the ability to change to vent/floor/defrost/etc.

i had this exact same problem, luckily i never did change out the actuator because i found my line broken one day when i replaced my battery. had i not had a battery go dead on me, i dont know if i would have ever found that tube (its tiny).

oh snap, i didnt realize you have a 5th gen, my suggest may or may not work for your model.

sorry

Well, thanks for the replies. I'll figure it out. I was trying to find where the vacuum line goes through the firewall, or into the car (cab, whatever.)

yea, sorry about that.