Dissected ac/heater control unit

Electrical & Ignition

  1. WissaMan

    WissaMan Member

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    The unit in our car was bad so we replaced it w/ a NOS unit. However, I was curious what was it was like inside to see if they could potentially be repaired. Here's a picture for anyone else that's interested in seeing what's inside.

    In the case of ours, all the little nibs for the vacuum connector were broken off. To me it looks like it got contaminated with oil or grease which caused the plastic to weaken.

    Inside there is a small rubber block with a recessed "H" pattern on it that redirects the vacuum. On ours, it was clogged up with some kind of black gunk. So even before the nibs broke off it probably wasn't working correctly. However, the rubber block itself still felt soft and pliable. If the nibs weren't broken off, it probably could've been cleaned up and reassembled and (seemingly) would work.

    IMG_20190527_184758596.jpg
     
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  2. WissaMan

    WissaMan Member

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    Oh I forgot to mention, the little tab on the slider thing that slides the rubber block back and forth broke of as well. You can see there's still the tab that slides the electrical switch side to side. When I took it apart, that little tab was still there but it broke off super easy, in fact I barely touched it. So that may've been weaked by the contaminant as well. The tab that moves the electrical switch still feels solid.

    That could probably be repaired with some effort. As long as there's NOS availability there's not much reason to try and repair, but if some day they are not....
     
  3. BLUPORT

    BLUPORT Carpe Diem Cras FCBO Gold Member

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    I did the same to my switch on my 68 Newport. $40+ for a new HVAC switch was hard to swallow, but I'm much happier now.
     
  4. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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    Somebody was rebuilding them. Problem was the price was more than most NOS switches, even overpriced ones.

    I looked at the "guts" of one that blew apart in a car I had. It looked like it could go back together without a lot of problems. Mine was in a bunch of pieces when I took it out, so figuring out what went where was too difficult at a time when they were readily available at any parts store.
     
  5. dart1962_440

    dart1962_440 Member

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    Where were you able to get the switch for $40.00 pr so. I could use one for my 68 300, std A/C.
     
  6. BLUPORT

    BLUPORT Carpe Diem Cras FCBO Gold Member

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  7. BLUPORT

    BLUPORT Carpe Diem Cras FCBO Gold Member

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    In my searches, I found the following part numbers: 587564, 2820487, 3895033, 2571501, 2096084, 3431020, 3502126, and 3895790 are all interchangeable for the same part. That's how I scored mine so cheap, it was the same part as a Van.
     
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  8. BillGrissom

    BillGrissom Active Member

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    Thanks. Very useful. $23 was an amazing price, but none left. Search "switch 3502126" in ebay turns up many for $75-80, which is still a good price. I recall when Paddock sold them for $99 in the early 1990's. You are correct that many later van parts interchange w/ our 1960's Mopars. I have found the same connectors on 80-90's Dodge vans and motor-homes, which had changed in the cars by the 1970's, such as the steering column connector. So, check the vans at the junkyard. It seems Mopar used up old factory stock by keeping them in the low-volume vans and especially motor-homes.

    On the A-body forum, a post years ago detailed rebuilding the electro-pneumatic HVAC switch. Many photos. My 65 Newport has 4-buttons since no factory AC. I rigged up a 5-button switch on a custom bracket to work, since I could buy those new. Google FABO w/ my name. I also added a relay on the "blower high" position, to shunt that large current around the HVAC and L-M-H switch. If not, the plastic will surely melt someday. A problem in most cars, and I did the same in my 1980's M-B to avoid a notorious fuse #8 (blower) melt. Of course, also an issue for the ALT & BAT feed-thrus in the bulkhead, unless a 65 like mine (special buss-bar feed-thrus).
     
  9. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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  10. WissaMan

    WissaMan Member

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    All good info... thanks!!!