New heater problem....

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xtriggerman

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Well, the AC no longer mixes heat to hold set temp in the car. A year ago I posted the blend door fix and rod mod and those are working fine, moving the lower blend door back & forth with the settings The heater core pipes are hot and I flushed them just to make sure there was no blockage. One guy on here years ago had the same issue and found the upper blend door was broken. He didn't say much about exactly how he went about getting at it and the particular method of fix. Boy, a picture would have been a HUGE plus but no.
So I hit Ebay up for an entire AC/heat air box with all the parts. Only $110 shipped. I figure I can peel that box apart first and see exactly what on the upper blend door can possible fail before I may have to remove the dash. I soooo not look forward to that. So maybe I can rig a "hole" fix of sorts. Maybe.....
 
Thank You for your reply & links. The Dash removal is most informing. My extra complete air box came in yesterday and I think I know what the problem is. The black blend door arm is all ready fixed from last year and it functions the lower grey arm to that lower blend door just fine. But still just cold AC blows no matter what. Well, what I think has happened is the same black plastic arm that gets brittle and has gotten the repair has broken inside the upper blend door squarish hole. So, you can fix the original broken cylinder part of that black arm but the square stud on its end that fits directly into the upper blend door pivot shaft will and has sheared off IMO, at this point. This makes the upper blend door non functional so there will be zero heat allowed to mix with the cold to hold a set temp on the ATC. The Fabulous thing is TODAY, we can order brand new blend door motors complete with a brand new blend door control arm! so, the repairing of the brittle black OEM arms is now a moot point. I ordered a new motor & arm for 17 bucks on Ebay. I'm hoping I can just pull the OEM motor back far enough to slip in the new white plastic control arm. If not, your pictured dash removal will be vital in guiding me threw the steps to get the new arm installed into the upper blend door shaft end.
Thanks.
 
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I think it best to still reinforce that arm or lever. From what i read, it isn't that they just get brittle and break. Its the measurement from the upper to lower arms that is tight and puts constant pressure on both levers. Unless you elongated the bottom hole, I would reinforce the arm with any of methods listed. wire/epoxy, clamp, even saw some used a compression fitting.
 
91 LSC SE said:
I think it best to still reinforce that arm or lever. From what i read, it isn't that they just get brittle and break. Its the measurement from the upper to lower arms that is tight and puts constant pressure on both levers. Unless you elongated the bottom hole, I would reinforce the arm with any of methods listed. wire/epoxy, clamp, even saw some used a compression fitting.
Click to expand...
Please go to the "How to articles" and you will see the arm repair AND the exact specifications needed to modify the metal arm that links the blend doors to the motor. After much research ( like you) I figured out the best approach to these 2 issues and your suggested cracked arm repair may have been my inspiration to take it to the next step as you can see in my How To Article. That said. The black plastic arm is flat out faulty plastic. You can repair its fractured cylinder part over the arm but when its square stud snaps off from the repaired area, it is no longer repairable. Thankfully, brand new arms are included with the new blend door motors as seen here all tho its a bad picture of the entire arm. I have one on its way to me for eval and install.
A-Premium 1x Heater Blend Door Actuator for Lincoln Mark VIII 1997-1998 604-915 | eBay
 
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