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.. It’s driving me mad.
Thanks

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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

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

"Harry Face" <harryface@webtv.net> wrote in message
news:9425-4227707B-103@storefull-3111.bay.webtv.net...
> 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
>
>
>
>
>
>
>

SSmith wrote:
>
> 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.. It’s driving me mad.
> Thanks

Sounds like your engine is out of coolant.
Better check it before it blows up.

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