AC blend door woas

[snowball]

hi all,

My 90 burb 350 R1500 is having a few issues when I turn on the AC. I get air from all the vents. Up down, in and out.

I can sometimes get it to work by snapping the throttle. I'll hear a snap and the blend door will close.

I think it's the actuator, but I can't find a part for it.

Any ideas would be greatly appreciated.

[mikentosh]

The AC/Heater blend door takes a two port vacuum actuator. In the early trucks (at least through '79) one of the ports is on the inside next to the arm, and there is a vacuum tube that comes up through a grommet in the top of the box. The later trucks (one I looked at was an '89) have a more standard actuator with both ports on the outside, and there is no longer a cutout or rubber grommet on the box itself.

I've only been able to find the later external 2-port actuator...try looking for an AC Delco 15-71438. I think they've been recently discontinued but they are available on eBay. The Parts Place now makes a reproduction version of it, if you can't find the AC Delco one.

If you happen to need a single port actuator (controls the vent doors), then they are available from Old Air Products.

[snowball]

Thanks Mike.

Found one on ebay.

Quick question. Does the heaterbox need to be removed or can i replace it as is.

Thanks!

[mikentosh]

Originally Posted by snowball

Thanks Mike.

Found one on ebay.

Quick question. Does the heaterbox need to be removed or can i replace it as is.

Thanks!

Unfortunately I think you'll need to pull the whole heater box...it's really not an easy part to get to. I've attached some photos that hopefully will give you a rough idea of where it goes. The biggest problem is that its bolted to the heater box from the inside...so you want to pull the whole box out, tilt it to have the cab side down/firewall side facing up. The driver's side half of the back box has a bunch of screws holding it to the rest of the case which you can remove. This cover won't come off as the actuator arm is still attached to the door itself...so you need to find a way to get a socket down there and remove the bolt holding the actuator arm. Once you've done that, the cover will come off and you can easily unbolt the actuator and install your new one.

Also please note that these photos are of two different heater boxes...the one with the bare metal back and silver actuator is from a '79, and the black/black one is from an '89.

[snowball]

Thanks Mike,

I think that makes sense. SO whould I able to access the actuator if I take off the plastic part that holds the blend door in place?

[mikentosh]

Originally Posted by snowball

Thanks Mike,

I think that makes sense. SO whould I able to access the actuator if I take off the plastic part that holds the blend door in place?

If you can somehow get to the back side of the blend door then you should be able to remove the speed nuts holding the actuator. In the '79 unit I tore down I didn't even want to try removing the blend door though as it looks like the rod that the door pivots on is pressed into the main plastic housing.

Let me know if you find a way to get access to it.

[snowball]

Will do. This is a 90 model so hopefully it can help others.