91 Buick Lesabre -defrost/heater not working properly!!

Can anyone give me some advise on my problem. Just recently in the last few days, my defrost/heater will be blowing hot air then all of a sudden it will start blowing cold air, then it will go back to blowing
hot air and vise-versa.. Its driving me mad. Thanks
--
Posted using the http://www.autoforumz.com interface, at author's request
Articles individually checked for conformance to usenet standards
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
probably a vacuum leak. Check to see if the hose connecting to the vacuum tank on the firewall came off. On my car the vac tank is to the left of the washer pump. The hose connects on the bottom . There may even be a plastic valve connected to the hose like on mine.
You might also have a bad vacuum diaphram or loose hose under the dashboard. That would require removing the lower black dash trim panels and listening for a loud SSSSSSssss noise.
Good Luck
========Harryface ======== 1991 Pontiac Bonneville LE 3800 V6 ( C ), Black/Slate Grey _~_~_~299, 999 miles_~_~_
~_~_~_~_U.S.A._~_~_~_~_~_
~~~The Former Fleet ~~~ 89 Cavalier Z 24 convertible 78 Holiday 88 coupe 68 LeSabre convertible 73 Impala sedan
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I was thinking the coolant might be low and the lines are getting air locked. Does it only go cold when you are at idle, and at highway speeds it's fine?
Steve

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
SSmith wrote:

Sounds like your engine is out of coolant. Better check it before it blows up.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
As far as checking the vacuum tank and hose, I might suggest you take the tank off and reseal it with some silicone sealer, My same car although it had heat would not blow air from the correct vents. It seems the tank was leaking from the seams. Took me forever to find that one. Good Luck JRE
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.