Heater Control Question

Hi all,

We have a 97 Grand Prix (3.8l) and I have a question about the heater controls, please.

The temperarature adjustment works fine, and the fan speed control works fine, but the adjustment for air flow direction/output does not work (the control to change from defrost to floor to vent, etc). It worked until 2-3 months ago, and it made a sound of air (vacuum?) when switching positions. Now it no longer switches, and it no longer makes any sound when adjusted.

Is this a vacuum operated switch, or should I should be looking at something different?

Any suggestions how to correct this would be greatly appreciated.

Mark in WI

check the vacuum supply hose that runs from the upper plenum, along the fenderwell near the battery, then through the firewall to the vacuum storage canister. This vacuum line is made of plastic, and become brittle with age. It's not uncommon for this line to get damaged when the battery is removed/replaced due to the tight spot and awkward way the battery comes in and out.

thanks richtazz,

I will look in to this, and assume from your post that this control is then vacuum operated.

Is there any chance you have a reference to anywhere online that shows what I am looking for, or should a mechanically inclined novice be able to identify this easily enough? I have a haynes manual for this, but no where in the thing does it refer to the plenum or the vacuum storage container.

If this vacuum line is bad and needs repair or replacement, is there and easy way to get at it, short of removing the heater/ac control assembly? I'm guessing this is the easiest way for me to identify the correct vacuum line, and follow if from the heater control outward, but you have any industry tricks or shortcuts, I'd be appreciative! I did just replace the blower motor last week, which was also on the way out, so I'm not a complete novice, lol.

Thanks again for the info,

Mark

if you find a section of the vacuum line under the hood that is broke you can cut the broken section out, and repair it with a section of rubber vacuum hose that fits snugly over the remaining plastic line.

thanks again richtazz,

just went to take a quick look, and I think I indeed found it - right by the bottom of the battery like you suggested.

From the firewall, it goes around like you described, then turns down ny the washer fluid reservoir. There is a 'T-splitter' where it branches off and goes under the reservoir, that seems to be intact. The other section goes down a bit, then makes a turn towards the engine. This is the section that is broken, goes about 2-3 inches and is just hanging there.

Right now I can not see where it goes, will need to remove the battery and possibly the washer fluid res., but I think I am on the right track.

Thanks again, will post back when I get at it!

Mark

richtazz,

Just gave it a go, and I found where that particular vacuum line went. It went down into a wiring cluster that ran down past the battery and into an electrical control panel in the engine compartment. The bad news is, it was so brittle that it kept breaking the more I tinkered with it and tried to get at it. I got a pc of tubing slightly larger, and was able to get it to fit over the top and in place, but it did not fix my issue, so either it was a vacuum tube for something else, or it was broken further down the line, far enough where I can't get at it.

Thanks for the tips, it was worth the effort just in case, but it looks to be a lost cause!!

Have a great new year,

Mark

Did the rubber hose have a good seal on the plastic vacuum tubbing. If it did not use some high quality silicone rubber like 3M or GE to make sure that you get a good seal so you do not loose the vacuum.

hi,

it did fit very snugly, I gave it a good pressure test against a pc of the vacuum tubing that broke away, and it fit very tightly and sealed well.

I am very sure the vacuum tube is split farther in than what I can get at (within the wiring cluster that I am NOT willing ot cut apart, lol). So, even if it WERE the right tube that needed fixin', there's just no fixing it!