Heat/AC Blend Doors

[USMC Hitman]

I noticed after the weather warmed up in the afternoons that I was getting warm air through the vents even when everything was off. I had replaced the heater core a few weeks prior and I know the temp adjustment worked, because after it heated up in the morning on my drive to work, I would have to turn down the temp. I knew the plastic piece on my blend door was broken, but didn't think it made that much difference. Now, I have to box out again to figure this out. I know I need to fix the broken part on the blend door, but I also noticed that the blend door doesn't close all the way(top pic). All my vacuum pods work, but I'm wondering if I didn't get the pivot rod between the door adjusted right or if my temp cable was not going all the way to close. Can someone tell me if this door is supposed to completely close? Both doors move when the lever moves. (bottom pic)

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[gmbellew]

I noticed after the weather warmed up in the afternoons that I was getting warm air through the vents even when everything was off. I had replaced the heater core a few weeks prior and I know the temp adjustment worked, because after it heated up in the morning on my drive to work, I would have to turn down the temp. I knew the plastic piece on my blend door was broken, but didn't think it made that much difference. Now, I have to box out again to figure this out. I know I need to fix the broken part on the blend door, but I also noticed that the blend door doesn't close all the way(top pic). All my vacuum pods work, but I'm wondering if I didn't get the pivot rod between the door adjusted right or if my temp cable was not going all the way to close. Can someone tell me if this door is supposed to completely close? Both doors move when the lever moves. (bottom pic)

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I am not 100% sure, as it has been a bit since I had things apart. but I think the connecting rod isn't correct. I think the bracket is flipped 180 degrees on the slave door.

 

[Jwernatl]

They make an aluminum piece that shuts the blend door. It makes all the difference in the world. I'll got it feom originalair.com.

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[Jwernatl]

Oh and it is supposed to be completely. Itll suck in the summer. When hot keeps blowing out.

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[USMC Hitman]

Picked up a metal replacement for the broken piece. Got the rod back in correct, too. Heater box is back in and checked the vacuum and the door closed all the way. Now to get the venting system parts back in without breaking anything. Had to take a mental break from doing that.

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[idahovette]

Yep, sometimes good to walk away and come back to it

 

[USMC Hitman]

All went back in correctly. Ran it this past weekend and with everything in the off position, no warm air coming through the vents. Seems to have fixed the problem. Now, on to bigger and better projects..... like new seats, custom center console...... double din touch screen with back up camera..... you know, fun stuff. LOL

 

[Captain Ron]

Charlie: I have the EXACT same issue on my 87 R30, air blowing through the vents at all times and increases with speed. All controls are off. While the other posters have been helpful did you ever find the exact source of the problem? Thanks!

 

[Snoots]

This plastic part may be your problem. They break often. Here's a nice replacement but for $33.00 I'd make my own from some scrap.

GM BILLET A/C Heater Box Blend-Air Door Clip for 70s & 80s Cars and Trucks #3018715

GM BILLET A/C Heater Box Blend-Air Door Clip for 70s & 80s Cars and Trucks #3018715

www.originalair.com

 

[75gmck25]

The original clip was made of nylon or plastic, and it’s quite a bit cheaper than that billet item above. https://www.americanclassic.com/197...VqmQfePWeoqF97uibISR-mXvNS3IvQEsaAsnsEALw_wcB.

IIRC, I had to cut the original pin that goes through the clip so I could get it out, and then make a new pin out of a small nail.

 

[Captain Ron]

Thanks guys, I'll check it out. The billet part is VERY - ummm - precious. Maybe my pack rats will appreciate it's beauty next time they invade my evaporator compartment!

 

[Jwernatl]

This plastic part may be your problem. They break often. Here's a nice replacement but for $33.00 I'd make my own from some scrap.

GM BILLET A/C Heater Box Blend-Air Door Clip for 70s & 80s Cars and Trucks #3018715

GM BILLET A/C Heater Box Blend-Air Door Clip for 70s & 80s Cars and Trucks #3018715

www.originalair.com

When I rebuilt my heater box I uesed the billet one — it is worth every dime.

If you use the plastic one - it will break again - it always does. - the air never stops blowing. Wait till you replace it, the difference is WOW.

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[Captain Ron]

Yup, it was the

1973-1987 Chevy GMC Truck A/C Diverter Valve Link Connector​

Thanks guys!

 

[454-k10]

If the diverter valve link connector is broken will it disable all blend door function? Mine is broken and air comes out the floor and will not switch to vent or defrost.

 

[Jwernatl]

Are all the vacuum lines connected?