I had this one in the General Forum but thought maybe it belonged here instead.
Sorry for beating this one to death but I've hit a wall in diagnosis on this one.
My HVAC air blower doesn't seem to be pumping out as much air as I think it should be. It doesn't make a difference if it's heater/just air or A/C. I've checked the vacuum hose that controls the flap, for leaks--Nothing.
I can actually hear the flap moving when I flip it to full defrost.
I removed the blower and checked the blower for the notorious "mouse nest"--aside from a couple of small leaves-Nothing. I stuck my arm/hand as far into the passages as I could to check for blockages--Nothing.
I "milked" all the "udders" and had some crap come out but still --Nothing.
I can hear the blower spinning like crazy but the air flow is nothing like what I think it should be.

What wold you suggest as the next thing to try.

Thanks in advance.



Bruce:

 

 

I do not believe that your vacuum motor canisters are getting the proper vacuum signals.

When you switch levels from floor to defrost to center vents, you should hear a vacuum line vent between each movement.

A vacuum signal controls all the damper shutters and damper doors.

Electrical actuators control the temperature damper doors.

If the vacuum signal isnt there, some of the vacuum motors can be in a dual position and HVAC Fam output will be exiting in more thanone location.

In this picture, the clear rubber strip on the RIGHT is the vacuum control manifold. The PURPLE vacuum hose is the
vacuum supply from the vacuum canister in the passengers fender well












VAcuum resivour in fender well. It gets its vacuum from the rear of the intake manifold:







I believe there is a FUSE for that module but I will have to look and see when I get home tonight.




Bill

 

Great--Thanks Bill. I look forward to your further guidance.

 

This is great info, mine is blowing from all outputs at the same time. Book shows inside fuses 18 and 27 as HVAC controls mine are fine. I found the purple line in your photos when I removed the under dash pnl. under the glove box. I hear no vaacum sound when I disconnect it from the black line leading towards the pass. side wheel well. I'll try to find the vaacum line at the back of the intake to see if its attached..Not looking foward to trying to find the canister in the wheel well.

Don't intend to hijack this but figure its all good info.

 

It might be the vacuum line coming from behind intake manifold sometimes these hose fry due to high heat.

 

Thanks Joe,
I opened the splash cover in the back of the right front wheel well. What a mess. discoverd that the vac. line through the firewall was broken, and some of the plastic vac. lines attached to the canister were cracked too. now I'm replacing the lines. Very tight working quarters inside the fender! We'll see what comes next, one thing leads to another with this car. It's a great looking car, at but I've found so many little things like this that makes me wonder about it's history...
Hope this helps another with like issues.

 

Repaired all the lines inside the fender, still nothing. I applied a vacuume to the purple line at the heater and selected each output with good results. Problem is outside of the firewall. I tried to see/feel the vac. line on the back of the BBK manifold, but there is not enough room. I'm afraid I may have to pull it off just to check the vacuume connection. I should hear a hissing sound at the line that connects to the canister from the manifold if its good shouldn't I?

 

Some times you hear the leak, and sometimes you don't. Many times, battery acid leaks destroy the nylon line that buried inside the main wiring harness. The issue could be a damaged line inside the harness.

follow the main harness behind the engine up as far as you can and sometimes you can see where the line enters the main harness.

I can inspect an OEM installation with a mirror and a good flashlight.

BC

 

just take the time to remove the intake Bill Curlee has a good write up on it with step by step photos and instructions now it take me about 15 minutes to remove intake with no problems as for the udders just pull them every other month just to keep the water flowing.

 

Success! I moved a couple of breather tubes and disconnected the two rear injector connections on the right side of the motor to gain very tight access to the vacuume connection on the rear of the manifold. Pulled on the Vac. tube and it came out, broken probably where it entered the wire bundle. Ran a new tube from the manifold to the vac. canister in the fender, low and behold, the selector switch now functions.
Thank you Bill and Joe.

FRC Carmichael this might be your problem as well.

On to the next problem, the reverse lockout selonoid repair.

 

I am having a similar problem.I have the automatic climate control AC system.99 C5.The blower does work and you can HEAR it working strong,but air does not blow very well.It's weak and not providing the flow it should through the venting whater ever function is chosen. It does switch to the defrost mode.But blows weak in that function too.
It does seem like there might not be vacuum, and could be the line you are all talking about ? IE :Would that line coming off the back of the intake manifold be the first thing for me to check ? It runs to a tank inside the fender ? Someone else also told me that the line deteriorates from battery acid and age heat or cracking ? The line that comes from the intake goes to the tank inside the fender and then trough the dash ? I hope I can trace it too.I experienced a simialr issue with a Grand National.It was an easy fix.All I had to do was replace the rubber hose from the intake to the T on the firewall.It Seems like a similar problem on my C5 So I am assuming it is a vacuum issue.Am I to conclude to check the source from the intake first off ?THANKS

 

COS C5. I am concluding that the line you replaced from the intake to the canister in the fender well was nylon ? You removed the inner fender skirt for access inside the fender ?
THANKS

 

C5 NEED FOR SPEED,
The picture posted by Bill Curlee with lables on the various lines and tank was taken with the right fender removed. If you open the passenger door and look into the fender you can see the Vac. canister. I removed the right front wheel, then the panel at the rear of the wheelwell. This exposed two ECMs which I dismounted, but left attached to the wiring. Removing the screw at the bottom rear of the fender let the fender flex (gently) outwards and gives more room to work.
I had many damaged lines, so starting at the manifold would not have made my process much easier. As Bill states in his posts, the line leaves the manifold, goes into the wiring harness behind the engine, exits the harness down below the battery then to the canister in the fender. This line is a small hard plastic tube and can be damaged.
I found a clear, 5/32 I.D. x6' vinyle tube made by Dayco, PN 80551 at Pepboys. It'll fit on the fittings, or over 1" stubs of the original plastic tubes left connected to the elbows in the system to replace damaged sections of the original plastic tubing. I ran this tubing from the manifold along the firewall to the canister to replace the line in the wiring harness. I used a vacuume pump to test the system held a vacuume after connecting the line to the canister, but before attaching to the rear of the manifold . Not maintaing a vacuume would indicate there are more leaks to be found. In hind sight, starting with this line might be smart to use a vacuume pump to test the system as repairs are made.

Good luck, hope this helps.

 

Thanks for the advice, the hands on exeperience, and passing on some tips on checking and replacing the line and also for the helpful pictures posted and advice given by a very experienced tech.I am rather surprised that I am having this probelm with my 1999 C5 only for the reason that it was stored in my garage for over a decade with a car cover on it since 2002.And the battery was removed from the car too.
But I guess sitting like that could also be a contributing factor. I can't complain though, because the rest of the car is perfect. And the car itself is a time capsule for me.And like the rest of us I enjoy driving
America's World class sports car !! Is it also possible that the system could be low on R134 ? I had it checked very quickly and thought the pressures were good.But can anyone tell me if low on R134 would cause the system not to blow strong ? I am thinking even if it was low on R134 it would still blow hard and strong but not cold ? Can anyone advise on that, before I start checking the vacuum lines.And perhaps I should check the R134 level more closely ? After all sitting for a decade with out running could have leaked some and causing the system not to blow strong ? Perhaps topping off the R134 would restore the blowing capacity ?THANKS

 

The R134 would have nothing to do with the blower motor operation.

 

I am pretty sure you are right about the R134 not having an effect on the blower.Reason why I ask that is because I did have similar problem with a 95 BUICK ROADMASTER that I also use.It was low on freon and blower got stronger when it was recharged.Just want to cover all the bases, because I am not familiar with the C5 system.I am pretty sure I will have to ttrace a vacuum leak.THANKS

 

Just wanted to thank everyone for the information in this thread. I bought a used Z06 yesterday and got a nice discount because the air was acting up on the test drive. The air distrubution was coming from defrost, face vent and floor equally. After purchasing the car I found the line coming from the vacuum canister to the blower box broken in two due to battery acid. Spliced the two ends together with some slightly larger rubber vaccum line from Autozone and all is good again. Cost me $4.71. I was banking on what I learned here before I commited to the car and it paid off. Thank you guys

 

anytime vette bro if someone dont have an answer someone will. and dont forget the Wave

 

After a long summer of enjoying driving my car, I finally took the time to check for the "cracked" air lines that control the HVAC dampers.
BINGO--just behind the battery the line was almost completely broken apart. I was able to find a hose that fit tightly over the existing hose and now have tons of air volume coming through the blower. The biggest part of the job was getting the confidence to tackle it.

Thanks to all who contributed to the help.
Now if only we could keep the snow away for another 6 months it would be spring .

Bruce