79 HVAC controller repair?
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Joined: Jul 2009
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From: Austin, Texas
79 HVAC controller repair?
I have another thread but could not update the title because I kept getting page errors so I apologize for the repost.
I have my HVAC controller out as part of the AC rework. The bottom side of the controller has a trace card with 4 metal traces. The outer one does not seem to be used. The inner three traces have a contact arm connected to the mode selector slider that runs along the trace as the slider is moved from Off to defrost.
One of the traces is broken and the metal tracevrolled back on both ends. What do these traces do and specifically the broken one? Any experience with repairing these traces?
I had previously seen a post where someone had found some metalic trace repair paint (my term) to repair circuit board traces but those were not contact type traces so I am unsre if that would work here or of a source.
Thnaks much.
I have my HVAC controller out as part of the AC rework. The bottom side of the controller has a trace card with 4 metal traces. The outer one does not seem to be used. The inner three traces have a contact arm connected to the mode selector slider that runs along the trace as the slider is moved from Off to defrost.
One of the traces is broken and the metal tracevrolled back on both ends. What do these traces do and specifically the broken one? Any experience with repairing these traces?
I had previously seen a post where someone had found some metalic trace repair paint (my term) to repair circuit board traces but those were not contact type traces so I am unsre if that would work here or of a source.
Thnaks much.
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Joined: May 2002
Posts: 2,558
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From: Columbus, Oh
I've seen a couple of the older hvac controllers and it looks like someone else tried to repair that thing...it looks terrible...no offense...
I might have a spare board laying around somewhere...i'll dig around the garage...
I might have a spare board laying around somewhere...i'll dig around the garage...
Thread Starter
Rennlist Member
Joined: Jul 2009
Posts: 1,919
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From: Austin, Texas
I was thinking of conductive silver paint. Can't be any worse that it is now.
I am still curious as to what those traces do.
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From: Honolulu and sometimes L.A.
Looks pretty grim. Once copper is off the board there is no way of getting it back on. Should be able to find a replacement for less work than fixing it. If you really had to fix it there are two ways you could think about it. 1) Purchase a piece of bare copper clad circuit board, cut the profile, and then copy the traces in ink. You can score where you want the edges of the copper on the new pcb with and exacto and then heat up the section of copper that you don't want with a really hot iron and slowly pull up the unwanted copper. You might be able to leave the unwanted copper in place and just score where you want the conduction broken, as manually pulling copper off a pcb can be slow and painfull work. Possible, and your total cost will be something like $3 for the copper clad. Hard work, and may take a few tries, but cheap. 2) Layout the artwork for the PCB in some freebee software package and order a replacement pcb from PCBexpress.com or 4pcb.com. They have different packages and price models but I would guess that one of them could do it for $25 to $50. You will have a learning curve on the layout package, but it should not be too bad.
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Joined: Oct 2012
Posts: 96
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From: San Antonio, Texas
Jim,
can you post the pictures of the Vacuum lines at the HVAC controller? I'm having trouble getting mine out and I want to ensure that if some come off that they go back in the right place.
currently the HVAC controller will only come out about 2 inches. it looks like the vacuum lines on one side and a 1/2 bundle on the left side are holding it in.
working to get the temperature select fiber optic lite back in place without full removal, but want to ensure I haven't pull a vacuum line by accident before I put it back together.
thanks sir,
Paul
can you post the pictures of the Vacuum lines at the HVAC controller? I'm having trouble getting mine out and I want to ensure that if some come off that they go back in the right place.
currently the HVAC controller will only come out about 2 inches. it looks like the vacuum lines on one side and a 1/2 bundle on the left side are holding it in.
working to get the temperature select fiber optic lite back in place without full removal, but want to ensure I haven't pull a vacuum line by accident before I put it back together.
thanks sir,
Paul
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I don't think it will be repairable but the traces don't usually do that - so even a failed controller with different issues could be used for a board swap (head varied by year - so get a compatible one). If that's the only issue with it you should be able to combine parts to make up a good one.
Alan
Alan
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Joined: Oct 2012
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From: San Antonio, Texas
Jim,
I found a good reference for the vacuum line connections and got them back in place. I had dislodged one during the controller removal so I'm very glad I double checked them before moving on.
I was not able to completely remove the controller, but got it out far enough to get the fiber optic light back in the slider where it belongs.
next task, for another day, will be to completely remove the controller and better retrain the temperature slider head as it still is loose and wiggles. you mentioned a retainer that connects to the back, but being that I couldn't get the controller all the way out, I opted to accept the minor victory with the fiber optic light and close everything back up.
in the end, the fiber optic light is not longer in the way so I can get full cold A/C again.
appreciate the advise, guidance, and pictures.
Paul
I found a good reference for the vacuum line connections and got them back in place. I had dislodged one during the controller removal so I'm very glad I double checked them before moving on.
I was not able to completely remove the controller, but got it out far enough to get the fiber optic light back in the slider where it belongs.
next task, for another day, will be to completely remove the controller and better retrain the temperature slider head as it still is loose and wiggles. you mentioned a retainer that connects to the back, but being that I couldn't get the controller all the way out, I opted to accept the minor victory with the fiber optic light and close everything back up.
in the end, the fiber optic light is not longer in the way so I can get full cold A/C again.
appreciate the advise, guidance, and pictures.
Paul
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Joined: May 2002
Posts: 2,558
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From: Columbus, Oh
Jim,
I found a good reference for the vacuum line connections and got them back in place. I had dislodged one during the controller removal so I'm very glad I double checked them before moving on.
I was not able to completely remove the controller, but got it out far enough to get the fiber optic light back in the slider where it belongs.
next task, for another day, will be to completely remove the controller and better retrain the temperature slider head as it still is loose and wiggles. you mentioned a retainer that connects to the back, but being that I couldn't get the controller all the way out, I opted to accept the minor victory with the fiber optic light and close everything back up.
in the end, the fiber optic light is not longer in the way so I can get full cold A/C again.
appreciate the advise, guidance, and pictures.
Paul
I found a good reference for the vacuum line connections and got them back in place. I had dislodged one during the controller removal so I'm very glad I double checked them before moving on.
I was not able to completely remove the controller, but got it out far enough to get the fiber optic light back in the slider where it belongs.
next task, for another day, will be to completely remove the controller and better retrain the temperature slider head as it still is loose and wiggles. you mentioned a retainer that connects to the back, but being that I couldn't get the controller all the way out, I opted to accept the minor victory with the fiber optic light and close everything back up.
in the end, the fiber optic light is not longer in the way so I can get full cold A/C again.
appreciate the advise, guidance, and pictures.
Paul
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Joined: Oct 2012
Posts: 96
Likes: 0
From: San Antonio, Texas
I actually used your (checkmate1996) post from back in 2009 here:
https://rennlist.com/forums/928-foru...agram-pic.html
along with this photo snagged from another thread.
http://s156.photobucket.com/user/ste...00085.jpg.html
your post let me see what the book recommends, and the photo let me see how the factory split is handled with the lines.
between the two, it all came together and worked.
I was living the "search is your friend" dream today.
https://rennlist.com/forums/928-foru...agram-pic.html
along with this photo snagged from another thread.
http://s156.photobucket.com/user/ste...00085.jpg.html
your post let me see what the book recommends, and the photo let me see how the factory split is handled with the lines.
between the two, it all came together and worked.
I was living the "search is your friend" dream today.
Rennlist Member
Joined: May 2002
Posts: 2,558
Likes: 216
From: Columbus, Oh
I actually used your (checkmate1996) post from back in 2009 here:
https://rennlist.com/forums/928-foru...agram-pic.html
along with this photo snagged from another thread.
http://s156.photobucket.com/user/ste...00085.jpg.html
your post let me see what the book recommends, and the photo let me see how the factory split is handled with the lines.
between the two, it all came together and worked.
I was living the "search is your friend" dream today.
https://rennlist.com/forums/928-foru...agram-pic.html
along with this photo snagged from another thread.
http://s156.photobucket.com/user/ste...00085.jpg.html
your post let me see what the book recommends, and the photo let me see how the factory split is handled with the lines.
between the two, it all came together and worked.
I was living the "search is your friend" dream today.
Glad that helped!
Rennlist Member
Joined: May 2003
Posts: 8,706
Likes: 152
From: Frankenmuth, Michigan
Jim,
I know you already have this, but since people are asking about HVAC vacuum, I figured it best to include here my resource as well.
http://928classics.com/4/post/2013/0...79-owners.html
Re your issue, I agree with the majority who suggest a good used replacement. The secondary is a good idea too, and I'm sure their will be a day where new replacement PCBs are necessary.
I know you already have this, but since people are asking about HVAC vacuum, I figured it best to include here my resource as well.
http://928classics.com/4/post/2013/0...79-owners.html
Re your issue, I agree with the majority who suggest a good used replacement. The secondary is a good idea too, and I'm sure their will be a day where new replacement PCBs are necessary.