96' Lesabre, vents switching to defrost.

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core - 15 Jul 2006 15:47 GMT

I am having an intermittent problem with the air conditioning on my
96' Lesabre. When the A/C is on (max, normal or bi-level),
occasionally the vents will switch to defrost mode and get stuck
there. Usually switching from heater to a/c max a few times resolves
the problem (temporarily), but sometimes I have to shut the engine off
to get the proper airflow again. It does not happen all the time, but
usually every 3rd day or so.

I notice it usually happens when coasting, a few seconds after I
remove my foot from the gas. This migh just be cooincedence, but I
thought I would mention it.

I recently had to replace a bit of rubber hose for the evap emissions
solenoid, it had rotted and cracked. I am thinking the same problem
might exist for the vacuum feed to the vent control, but cant seem to
find where it connects to the engine.

thanks

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Edwin Pawlowski - 15 Jul 2006 16:31 GMT

"core" <nospam@yahoo.com> wrote in message

> I notice it usually happens when coasting, a few seconds after I
> remove my foot from the gas. This migh just be cooincedence, but I
> thought I would mention it.

Engine vacuum is highest when you are coasting, throttle closed.

> I recently had to replace a bit of rubber hose for the evap emissions
> solenoid, it had rotted and cracked. I am thinking the same problem
> might exist for the vacuum feed to the vent control, but cant seem to
> find where it connects to the engine.

At the least, go back and check that hose you replaced to be sure nothing
else was disturbed.

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core - 15 Jul 2006 17:32 GMT

>> I recently had to replace a bit of rubber hose for the evap emissions
>> solenoid, it had rotted and cracked. I am thinking the same problem
[quoted text clipped - 3 lines]
>At the least, go back and check that hose you replaced to be sure nothing
>else was disturbed.

There are two lines on the evap solenoid, one runs back to the
throttle body and the other goes to the can. All on the front of the
engine. Nothing else was disturbed (as far as I can tell) it was a
simple fix that did not take much effort.

I followed the other vacuum lines to see where they went, and could
not find anything that goes through the firewall. The diagrams for
the vacuum system show the feed line going through the upper passenger
side of the firewall (viewed from the inside). I could not find any
diagrams online for the engine compartment.

Another thing I though of was that the increased vacuum during
coasting is collapsing the tube somewhere blocking the flow. I will
have to check if its getting pinched somewhere possibly.

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core - 16 Jul 2006 00:24 GMT

>Another thing I though of was that the increased vacuum during
>coasting is collapsing the tube somewhere blocking the flow. I will
>have to check if its getting pinched somewhere possibly.

Update, I found where the vacuum line feeds in from. Its right wherer
the brake booster vacuum line hooks up. It has a plastic tube that is
stuffed into the wiring harness, thats why I could not find it.

Anyway, everything there looks fine. Since the tube is plastic with a
rubber transition, my collapsed tube theory is likely way off.

As I drove today, it happend again. This time the onyl way to get it
working again was to shut the cr off for .5 hour or so. Then it
started working ok again.

Think the controls are shot?

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KjunRaven - 16 Jul 2006 00:58 GMT

core <nospam@yahoo.com> wrote in news:n1uib2djprj6ak9vmeau7klslv10qh139s@
4ax.com:

>>Another thing I though of was that the increased vacuum during
>>coasting is collapsing the tube somewhere blocking the flow. I will
[quoted text clipped - 12 lines]
>
> Think the controls are shot?

could be the controls. could be!.....if it were I = remove controls, cut
supply vac. line in convenient spot, 'T' in hose to attach vac. guage, hang
vac. guage under dash, install controls, drive normally until it rears its
ugly head again, observe vac. guage for proper vac. but then again im a
stickler for diagnosis b4 replacement on everything possible......tips =
supply vac is purple on the old vac. driven sytems if i remember
correctly..you also have a vac. cannister (plastic ball) somewhere, it has
a check valve built in it........kjun

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