I am sorry sir but your diverter gate axle is broken of inside the plenum. You can bet the vacuum motor is working properly. To test it just disengage the linkage to the diverter actuator lever and experiment with the controls. You will see the rod moving up and down as the motor does its thing.

 

You will need to do surgery to the plenum, my friend. Remove the knee guards and a module that is fixed to the front of the plenum and all the plugs and wiring harness. Behind this module in front is where you cut the rectangular hole which you use to fish inside with your hand and remove what is left of the diverter gate. The other remnant of broken axle is still fixed to the white plastic drive lever outside(drivers side). I can send you photos if you like. I could not find any part number on the gate so I re affixed the broken axle pieces with a monster lag screw running lengthwise. I did not spend one red cent on my repair project, still I would advise buying a new diverter gate.

 

Kennycraze, could you please post some photos of your lag screw repair. Tks. 92cabby

 

I am sorry 92,
The photos I had were apparantly deleted at some stage as I did the repair many months ago. I remember just using a longer than normal drywall screw, in addition to glue. You want a slender screw about 1&3/4 to 2 inches. You need to adequately countersink the short stub piece and use a 5/32 drill for the first 5/8 inches of pilot hole. Then a smaller drill into the axle where the threads have to bite. Be careful and keep it straight. Make sure the screw head does not interfere and white plastic lever piece has sufficient room to engage the locking clip after sliding on the axle end.

 

Cutting the airbox is certainly NOT the proper way to replace this part. Will it work? probably, but it will likely affect your air-flow, not to mention looking horrible & backyard engineered. If you're like me, do it the proper way, and you'll thank yourself in the longrun.

In my experience, anytime you start "ghetto rigging" things, you will likely cause more damage than repair.

The proper procedure is to remove the entire dashboard assembly, remove the HVAC assembly, and replace the "valve" door. While you're in there, you'd be wise to replace the heater core.

A good way to check for a broken valve is to (underneath your dash, driver's side, toward the center of the vehicle), grab a hold of the white piece that has a spring wrapped around it, which is also levered against the mating end. If that white piece moves around freely in every direction (or almost every direction), you've got a broken valve.

I did this job a couple weeks ago and it was a major PITA. Prior to that, I had never done it before so it took me a total of around 14 hours. The redeeming thing though, is that once it's all out, putting it back in goes a LOT faster (probably half the time, if not less).

 

Firstly Scuba,
I did not engineer this idea. I followed advise from someone else who had done the job. Why would you worry about cutting the plenum?? It is only a plenum! My air flow has not been compromised one iota. I patched and siliconed the opening afer replacing the plastic piece I removed. Just a few metal screws, a bit of tin and,.....Bob is your uncle! Who said anything was visible afterwords? I have not replaced even the knee guard and I cannot notice any thing behind the module box suggesting anything was cut or altered. If you think replacing the entire HVAC system is easier then.... go for it. That would be utter foolishness! GM ought to be chastised(sued) for building vehicles like this whose safety features regularly malfunction. Fisrt it was the windshield wiper module, then the headlights because a of a short in the tilt steering, then the defrost. Obviously they have done their best to interfere with my visibility and wish to get all Blazer owners killed in traffic.

 

Kennycraze,



Thanks for the information. We have decided to make this repair when warm weather gets here. Currently we're using the old "Bent coat hanger will keep your feet from freezing" trick. We haven't yet decided how we're going to implement the repair. If possible, I'd like to replace any of the hard to get to plastic parts with homemade aluminum parts. Once we tear it all apart we'll have a better idea of what we can or can't fabricate. And, there are a lot of posts concerning heater core reliability. We'll also have to evaluate the core and replace it if necessary. Again, we appreciate any pertinent information,cheers, 92cabby

 

Coat hanger trick worked like a charm! Thanks so much! My no longer cold feet thank you as well.

 

Hey guys and gals....first post here, I just signed up yesterday, and was searching for info about doing this job.
I work on cars, trucks, tractors, ag machinery and the like, pretty much anything. I'm in my 11th year of running my own shop and I worked for a General Motors dealership for several years before that.


Anyway, I just wanted to say thank you for the info, and I also wanted to mention that this broken door can be replaced without pulling the dash, or cutting a hole.....I did it. After removing the air deflector at the very bottom of the heater box,(the plastic piece that diverts the air to either side of the hump....two screws, well one if you don't put the back one closest to the firewall back in) you can reach up into the rectangular hole and pull out the broken door, and carefully, (and with lots of patience) put the new door right up in the hole. Sounds easy, I didn't know if I could do it or not, and probably spent wayyyy too much time doing it, but it can be done.
Seems like a lot of work on a 15 year old ZR2, but the customer wanted it done. I'm actually surprised that this is the first one that I've ever came across. Anyway, thanks again.


Travis

 

Interesting. you did not have to cut the plenum! I'm not sure I understand how you did the job. Since I repaired my broken diverter gate and axle months ago, I have acquired another at a local Pick and Pull auto wrecker. Honestly, I had to smash the plenum to bits to get it out in one piece!
It was not too difficult as the plastic formed plenum was quite brittle.

At least this one is nice and straight. If these get curved they will be prone to jam and then be broken by the powerful vacuum motor.
I have to admit I am having difficulty with the axle locking into the boss properly inside the plenum where I can't see anything. I am doing this by feel only. It needs to slide into the boss all the way and then lock and not flop around.
There are not instructions for this repair.