Good evening all - new to the Corvette world and purchased a very low mileage 89 coup (48K) with external cosmetic issues (Interior is in VERY good condition - the thing sat in a barn for years - it's still wearing Eagle VR 45's). Taking care of the external cosmetic issues but running into one after another smaller issues. The motor runs excellent - Now I am stumped and am hoping someone can help me. Evidently the nice farmer that owned this previously decided at some point that he didn't need the vacuum "ball", ganked that out and completely bypassed the EECS valve (it's there but nothing connected to it). Sooooo, of course the AC blend door doesn't work and just blows hot air (I should note that the compressor does kick on - and, if I bypass the heater core the AC blows COLD but with the heater core connected the heat overrides the AC). It does have the automatic climate control and all of the internal diverters work as they should (defrost, vent, floor, etc.). It is just the lovely blend door under the hood. I think I've ordered all of the parts to put it back together right just need someone with an 89 to take some good pictures of vacuum lines in the drivers side front of the car where the ball should be - and (please!) what connects to what. Thank you all for the help bringing this one back to life and apologize if I did not get the terminology correct.

 

oooooo k...

So "barn kept" isn;t quite as good as "garage kept" ?
Interesting....its usually the interior that's destroyed from rats eating the foam and plastics...wire insulation, everything.

I'm gonna jump in with no direct knowledge of an 89, BUT I do know about the 87, which is mechanically the same thing.

IIRC the a/c system does NOT use a vac reservoir because the lines themselves add up to be sufficient volume to operate the vacuum actuators effectively. Assuming this IS the opt-68 auto climate control,. you have to get the ONE vacuum feed line to the interior that enters the cabin behind the engine on the firewall. I think its just left of the distributer....that line also has a "T" that goes to the cruise control and the "ball" that is the vac reservoir for the A.I.R. valves, diverter and dump valve. All that is to direct air to the cat or the exhaust manifolds.... The ONLY thing in common with the a/c is the vac line and that's just a T.

Assuming you DO have vac to the cabin you now have to get to the a/c programmer and be sure its got vac AND electrical. The a/c is 3 major pieces that must communicate with each other AND the ECM (ECU, PCM, whatever).
The control head gets the command from YOU. It then has the link to the BCM which supplies power to everything, programmer included. The programmer directs the airflow by way of temp signals from sensors and control head settings,..

Get your FSM out and do the reading on this. The a/c system is self diagnosing and the FSM tells you how to get it to display the codes that will be of tremendous help.
The control head may need to be cleaned and plugs checked. not difficult to remove, the programmer however will ruin your attitude about Corvettes... Very UN-Fun.
Your FSM will also show you where the cabin vac lines are run and what color they should be. They are color coded lines under the dash. Only 2 or 3, but they are important. Don't know if the blend door is vac or electric.
I DO know that later yrs that ARE electric are famous for certain problems that prevent them from moving the door....the linkage is one of these problems. So, figure out if its vac or electric. Someone here should know that about the 89....and the FSM certainly will tell you.

You said that the vents were ALL working as they should??????

So you're saying that when you push the DEF button the vents operate and send all the air flow to the defroster? and then hitting the "auto" button will get air thru the dash vents?
IF that's true, the cabin vac supply is fine. It may be just the blend door actuator. The FSM will tell you where and how to find the actuator. Mine is accessible from the passenger side floor at the rt side foot well...up, against the wall. Yours will be similar.

Now, IF your vac is good and the programmer is redirecting air flow, with the exception of the temps....do this....

the control head has defaults in case of a failure. (this)
run the auto display all the way to 60. That's the default for cold. That tells the programmer and everything else to send cold ONLY.
Heat does the same trick when set to 90. heat ONLY.

See if that does anything. If it does, I'd say you have a cabin temp sensor that's bad,, or the control head. Again....the diagnostic will tell you what, if anything electrical has failed.

farmer John d/c the emissions system because that's what all Bubba's do to things they do not understand. Take it off. "it don't need that...whats it do anyway ?"

The vac lines under the hood are pretty simple...find the 2 fittings on the rear of the plenum. One line should run toward the front of the engine and maybe a T to the fuel regulator...
The 2nd fitting runs around behind the plenum and THIS is the one you want to trace for the CC and the cabin vac supply line. The vac line enters the firewall near the distributer. There will be (should be) a check valve by the dist, with a line to the firewall and the other goes to the cruise and splits once again to the "ball" and emissions..charcoal can etc.
The "ball" on the 89 might be for CC and emissions...I do not know why they would add a reservoir to the a/c system after many yrs without. It seems like the things that I was reading about involved the vac system and the ball was necessary for the cruise to be stable so its actuator would not move the throttle around with minor changes in manifold pressure...this is also where I read that the vac lines in the a/c system were enough volume to operate the system, so it did not need a reservoir. I thought that was strange that GM actually calculated the volume of X-number of inches of 1/16" vac line...but I guess they paid someone to do that.

Hope this helps....if running the defaults does not yield a result, you have a simple belnd door issue that at least tells you the rest of the system is healthy.

Enjoy your new car....half the fun of owning a Corvette is working on the Corvette !

Good luck !~

 

Thank you so much -It does help a lot! Yes all of the internal vents work as they should - defrost, vent, floor, etc. I was afraid you would mention the programmer, from everything I've read about them they are prone to failure, not inexpensive, and discontinued. Farmer John's solution in the summer was bypass the heater core at the firewall and the thing would freeze you out of the cabin. Still not sure why the EECS was bypassed or if it will pass emission without it? Still wouldn't mind some kind soul to provide a good picture of the drivers side front of the car showing the vacuum ball and the EECS area for a reference. Here's a pic of the interior BTW, I was surprised how well this stood up - not a single crack in the dash either.

 

Nice save, I'm sure you will have a nice driver when your done.

With everything your doing it may be time to invest in a FSM if you have not already.

 

congrats for your new ride,interior are mint,i see just a portion of waterstripping and they seems good too...fix litlle bugs and enjoiy

Alberto-Italy

 

yeah,
your next investment has to be the FSM set. NOT a $19 Hyeneas manual from Autogroan, or a Chitlens manual from PeePBoys....a REAL GM factory service manual.

As previously stated they are NOT terribly expensive for what they offer. Information is priceless and these books offer the CORRECT information !
That's as good of a deal as you will ever find for the 2 most valuable books on the planet to a new Corvette owner.
The ONLY other book that's as important as a FSM would be a Bible. You're gonna need that one as well before this is over.

Seriously, every question, every test procedure, every detail every torque spec, every drawing for everything is in these 2 books ! The 2nd book is electrical ONLY. Drawings for every system in the car and every possible option that GM offered.

Your detail for vac lines is also in there...

I will get mine out and see if I can translate the drawing. IF I can scan it and send a decent pic from the scan I will do that.

The vac mess in the nose is not complicated. the "ball" has a small line to it from the battery side of the car, where the vac line originates like I told you, from the plenum, past the dist, to the cruise, where a T splits it and sends one line to the ball.

Is the charcoal can still there? and the A.I.R. solenoid? what about the 2 A.I.R. control valves by the compressor?

There are other reasons why you want all that crap hooked up....besides emissions, you need it to make everything work right. People CANNOT just start disconnecting stuff 'cause you don't like it, on a computer controlled engine !
I know previous owner Bubba, was responsible but you need to understand that the computer looks for signals from many sensors, then it activates these things and wants a response from another part, and if ANY of this is missing or d/c....the rest of the system cannot operate properly. EGR valve for example. the engine wants and NEEDS that. The PCV system,...That's a BIG deal ! the engine NEEDS that just like it NEEDS the o2 sensor(s) for info.

You NEED the FSM !

From what you are telling us, your a/c problem has nothing to do with all the bubba rigged stuff under the hood. All that damage is truly unfortunate, since its now on YOU to figure out whats whats and get it right. Hell, just trying to figure out what's missing can be a challenge ~!

I cannot believe that a car with < 50K had things taken apart under the hood....that's SAD. Thank God you found this car and saved it.

From your description of the a/c, the blend door actuator linkage may be broken, or maybe the blend door actuator has simply failed. Its easy enough to watch it operate. Have someone else push buttons and you get your face in there so you can see it. First, see if its vac or electric operated. Then go from there. You also might have the heater hose valve in the pipe next to the evaporator core. I KNOW that 87 had this and it was discontinued at some point. Yours may have it, may not. See if that valve is working to shut off the hot water flow TO the core....remember the DEFAULT temp settings. A setting of 60* orders the system to full COLD and no matter what the temp actually is, it must send full cold thru the vents. Same for heat....90* there. Run the temps to these settings and watch the blend door to see if anything happens as somebody else pushes the "auto" button while at max hot or cold.

here are a couple FleaBay listings.....

http://www.ebay.com/itm/1989-Chevrolet-Corvette-Shop-Service-Repair-Manual-CD-Engine-Drivetrain-Wiring-/301174348131?pt=Motors_Manuals_Literature&hash=item461f63d963&vxp=mtr

http://www.ebay.com/itm/1989-Chevrolet-Corvette-service-shop-dealer-repair-manual-/311069182427?pt=Motors_Manuals_Literature&hash=item486d2b09db&vxp=mtr

http://www.ebay.com/itm/1989-Chevrolet-Corvette-Shop-Service-Repair-Manual-CD-Engine-Drivetrain-Factory-/400443169350?pt=Motors_Manuals_Literature&hash=item5d3c45da46&vxp=mtr
Your chance of success are almost guaranteed if you have these books/CD to answer any of your questions. These are a lot more accurate than I am...and the typing is already done !

 

First of all, thank you for the help! I will certainly order the FSM's - here's what I discovered this evening, the vacuum line from the back of the plenum goes to the check valve under the plenum, one line runs into the firewall, the other to a "T" connector - one runs to the cruise (which does work BTW), the other directly to the charcoal canister. That's it. I'm guessing that it was supposed to run into the vacuum ball. But what connects to the charcoal canister and EECS? Here is a picture of what is there now.

 

You can check the blend door by removing the blower control module. This guy:



You can see the blend door by looking into the opening. Set the HVAC to 60° and check the blend door position (first pic -- covering the heater core).



Set the HVAC to 90° and check the blend door again (second pic -- blocking the air duct opening and directing the air flow into the heater core).



If the blend door is not working correctly then this thread might be useful:

http://forums.corvetteforum.com/c4-t...schematic.html

I have an '86 and I know some of the vacuum connections to the canister changed from year to year, but this is what I have (spherical vacuum tank barely visible in the lower left):



There should be a diagram of the vacuum hoses on the top of the radiator shroud on the driver's side.

 

First things first! A HUGE thank you to the Forum Members who are so helpful! All of the Farmer John vacuum issues are resolved as well as the Blend Door. Turns out it was the AC Programmer. Ordered a replacement and absolutely everything on the car works as it should! Now one last question - as difficult as it was to find a good Programmer does anyone know if anyone is rebuilding these? Wouldn't mind having my defective one repaired as a spare. Man, aren't they fun to replace? Was upside down in the drivers seat on the floor so long that I believe blood was beginning to pool in the back of my head.

 

Great info

Thanks

 

Bryan A. Thompson is repairing HVAC systems, including the programmer:

http://www.batee.com/corvette/acrepair/c68pgmrboard/

When I work under there I lie on the frame rail. I have 6 titanium screws in my spine from sciatica and a degenerated disk and they are right where the frame hits. :-(

 

Thanks! I'll contact Bryan and see if he can help me have a hot spare available. Yes, it is quite a miserable chore to work under these dash boards. On a positive note, at least it wasn't the blend door motor!