99frccorvette

What an AWESOME write up!!! this just came in handy and i just fixed this same problem

66dts-v

I need to fix mine, now.

Awesome write up.

Stefvette

Awesome,

I will send this write-up to my mechanic so he will know how to fix.

Thanks

BigDaveOnBass

I dug into mine today and found a vacuum line under the battery box completely broken in two. I put a slice on it and put it back together with zip ties (i tugged on them to make sure they were secure) but it's still blowing out all vents. Frustrating....

madmatt9471

The patch may not be good enough.

Your best bet might to replace the line completely from the rear of the manifold to the valve in the fender and eliminate any of the old plastic line and old 90 elbows.

Thanks, Matt

Bill Curlee

100% Correct... If you found one issue, its most likely riddled with holes and cracks.

BC

hron61

Nice write up, thank you.

I read it over and over but don't see a parts list that i need to get to do this.
Am i missing something?
I need to tackle this on my c5 vert soon as well.

ArtGle

Love this thread. Just read from start to finish.
My problem is that I'm getting NO VACUUM out to the RED vacuum line to the Heater side of the "Defrost/Heater" diaphragm. UGH.

Just got off the phone with Mark at VetteNuts.
Paid immediately via paypal.

But thought I'd give you a NICER picture of that "Vacuum Block"

Oh, on a 99 Coupe with the "CJ2" option, which is the "A/C Electronic) option.
The GM part number is : 52469694

Got that from the C5 Parts and price list that a fellow member posted in PDF format.

(afterthought) I've added the 'diagram' for this from my Factory Service Manual as well.

madmatt9471

Awesome!

Thanks,Matt

Bill Curlee

Here is a picture of the AIR BOX removed from the car:

ArtGle

Love the pix. Thanks.
Got a replacement part coming from Mark at VetteNuts!
Great Price, and verified shipped yesterday, the day I ordered it. YAY MARK!!!

ArtGle

The "Heater/Defrost" Door is controlled by the Vacuum Diaphragm.
The Diaphragm is a "THREE POSITION" type.
No Vacuum, it centers, and allows air to flow out BOTH the Defrost and Heat (foot) vents.
Depending on which MODE you place the Electronic Control in, either Defrost, or Heat (foot) vacuum is applied the desired side of that diaphragm, (Red or Yellow) by the Vacuum Solenoid.
Everything on mine works "EXCEPT" RED.... UGH.

And after all my searching, someone here recommended Mark at VetteNuts.

YAY.... Great Price.

I'll let you know if, (but I'm pretty sure it will) this fixes my problem.

MKIVBB

Great write up, and thanks a ton for taking the time! But is there any way you can label some of the pics maybe with an arrow or something pointing to the suspect vacuum line? My Z06 just started doing this today. Gonna tackle it this weekend. Thanks!

Bill Curlee

Art... Sounds like you either have a broken RED LINE or the controller isn't working for that vacuum solenoid can.

Keep your OLD Controller.. I would like to dissect it and see why it failed..

Bill

MKIVBB

I'm in the middle of doing this right now, but can't seem to find the vacuum supply line. Where in this picture is it supposed to be?

I removed my battery and battery tray to give more space, and I believe I found the end of the vacuum supply line that goes into the fenderwell, but it looks like is wrapped up in a big loom of wires that goes back towards the engine.

Am I lost here?

MKIVBB

Ok, with a mirror and flashlight I finally saw the vacuum nipple on the back of the intake manifold, and low and behold - the right angle rubber fitting that was supposed to be on it was unplugged! I re-plugged it in, am cleaning under the battery (didn't see any signs of acid, but just doing some housekeeping cleaning the dirt/grime build up under there) and hopefully once I get the battery back in my problem will be solved. Fingers crossed!

madmatt9471

It is in the wire loom and disappears into it and reappears out near the bottom past the battery and tray, down by the PCM in the fender -

Sounds like you should be in business once all is back together -

Let us know how it goes!

Thanks,Matt

MKIVBB

Everything worked great once I plugged the hose back into the MAP sensor on the back of the manifold. Glad it was something simple. No idea how that damn thing came off.

Thanks to all of you guys who posted the info and pics! Definitely made this a smooth deal.

ArtGle

I believe I still have it out in the shed.
I'll get it to you soon.

Right now dealing with open circuit on Intake Air Temp Sensor.

Tan lead to PCM... Open circuit. UGH.

strahst

Thanks to all on this site. This helped me troubleshoot and locate a disconnected HVAC vac line on the back of the manifold. Now lots of stuff work that didn't. Thanks soooo much.