AC switches internittent

[WARP TEN]

Originally Posted by scottfab

As with so many of the issues that come up on the car this is an old and repeating one. Yes by all means clean the contacts. The reason they fail is oxidation. The metals used are a cheap tin alloy. Cheaper than it should have been.
Coat them with dielectric grease when re-inserting the head contacts.
This keep oxygen away from them prolonging the time it takes to oxidize. It's not the buttons it's the connector.
There is another thread somewhere on this but I'll restate the cause from the perspective of a classmate of mine who holds a PhD and 26 patents in the field of metal to metal contact issues. It is the result of dendrite growth and oxidation.

Thanks for all the input everyone. I will make it my mission to wipe out dendrite growth! -- Bob

[Bob Eyres]

Thanks guys. This has been happening to me intermittently since I've owned the car. Sounds like a good weekend project.

[WARP TEN]

Well I followed all your bits of advice and fixed the issues with my window and A/C switches this weekend. Took a couple of hours. Sorry I did not take any pictures but as many noted it was fairly straight forward.

The window switch trim panel holding the switches comes off easily with 2 screws and the only tricky part was once the switch was off the trim panel at the workbench it was hard to actually open the switch. There are about five little plastic snap fasteners that had to all be carefully pried away from the switch case simultaneously. I did it by holding each open with a little sliver of wood cut from the thin end of a shim. Once all were held open I was able to carefully work the switch case apart without breaking the tabs. Once off I found little rocker contacts that were moved by the switches. Lifted out, several of the contacts showed some arcing residue. One in particular was very black and rough; I presume this was the one for the passenger side that wouldn't let the window go up. I used 400 grit wet dry sandpaper on them and then polished with a stiff brush on a Dremel tool (The contacts attached to the switch are a bit hard to get at otherwise). A little grease where the switches rub on the contact levers and it all went back together easily. They seem to now work fine.

The A/C control head also came out in a straight forward manner following instructions in the FSM. One hint not noted it the manual: As a first step to removing the console trim panel, remove the hinged console lid (four hex screws). Otherwise it is hard to get the trim piece off and impossible to get it on again. On the workbench, the A/C control head comes apart easily with small hex head screws. The switch mechanism is interesting: It is a rubber pad behind the switches that, when a button is pushed, pressed what looks like a small piece of carbon against a small design on a circuit board. This apparently completes a circuit. Unlike the window switches, it was hard to tell why the switches were not functioning all the time. I carefully wiped the carbon points and the circuit board with contact cleaner a (very) lightly scuffed the contact on the board with 400 grit w/d sandpaper. It went back together easily and also seems to work fine now.

Thanks for all the helpful advice. --Bob

[Franke]

Bob, only one thing I can think of is that I was told in electronics class not to use sand paper to clean contacts as the grit can become embedded in the contact material. We were told to use a fine contact file. I see you used a wire brush to polish them which is helpful. As far as the contact pads... they are the same type as what is used in electronic calculators, cell phones etc. I wouldn't scuff them with 400 paper, just use contact cleaner so as not to remove the contact pads. Glad all is well now and I will be doing the same thing on my door window switch. I like your idea of using shims.

[Dynomite]

Originally Posted by WARP TEN

Well I followed all your bits of advice and fixed the issues with my window and A/C switches this weekend. Took a couple of hours. Sorry I did not take any pictures but as many noted it was fairly straight forward.

Window Switches:
1. The window switch trim panel holding the switches comes off easily with 2 screws and the only tricky part was once the switch was off the trim panel at the workbench it was hard to actually open the switch.
2. There are about five little plastic snap fasteners that had to all be carefully pried away from the switch case simultaneously. I did it by holding each open with a little sliver of wood cut from the thin end of a shim.
3. Once all were held open I was able to carefully work the switch case apart without breaking the tabs.
4. Once off I found little rocker contacts that were moved by the switches. Lifted out, several of the contacts showed some arcing residue.
5. One in particular was very black and rough; I presume this was the one for the passenger side that wouldn't let the window go up. I used 400 grit wet dry sandpaper on them and then polished with a stiff brush on a Dremel tool (The contacts attached to the switch are a bit hard to get at otherwise). As Franke and Scottfab suggest, the best method to clean electrical contacts would be with the use of a contact file or a pencil eraser. Not a pen eraser but a pencil eraser. It is an extremely fine rubbing compound.
6. A little grease where the switches rub on the contact levers and it all went back together easily. They seem to now work fine.

The A/C control head also came out in a straight forward manner following instructions in the FSM.
1. One hint not noted it the manual....As a first step to removing the console trim panel, remove the hinged console lid (four hex screws). Otherwise it is hard to get the trim piece off and impossible to get it on again.
2. On the workbench, the A/C control head comes apart easily with small hex head screws.
3. The switch mechanism is interesting: It is a rubber pad behind the switches that, when a button is pushed, pressed what looks like a small piece of carbon against a small design on a circuit board. This apparently completes a circuit. Unlike the window switches, it was hard to tell why the switches were not functioning all the time.
4. After talking with Marc Haibeck about fixing my A/C head, the problem is apparently not with the rubber gasket behind the buttons but with a connector between the circuit board that is screwed to the button faceplate (and holds the rubber gasket in place). So you don't even have to take the circuit board off the faceplate after all. On the face plate circuit board are a bunch of fine thin contact prongs that when assembled fit into corresponding sockets in the A/C head. An unusual connector if you will. It is these prongs that get dirty and lose contact from repeated button pushing (they move ever so slightly when the buttons are pushed according to Marc. ) On mine I cleaned them as well so everything works. Marc says he has fixed about 30 A/C heads by simply cleaning these connector prongs.

5. It went back together easily and also seems to work fine now.

--Bob

Window Switches (91').................................................. .........AC Control Head (91')

[WARP TEN]

Originally Posted by Franke

Bob, only one thing I can think of is that I was told in electronics class not to use sand paper to clean contacts as the grit can become embedded in the contact material. We were told to use a fine contact file. I see you used a wire brush to polish them which is helpful. As far as the contact pads... they are the same type as what is used in electronic calculators, cell phones etc. I wouldn't scuff them with 400 paper, just use contact cleaner so as not to remove the contact pads. Glad all is well now and I will be doing the same thing on my door window switch. I like your idea of using shims.

Probably right about using sandpaper Franke--although the wet dry stuff holds its grit pretty well and there is a very confined space for the fixed contacts in the window switch so my usual ignition contacts file (from the old days) wouldn't fit. I did carefully clean the contacts afterwards with cleaner and cloth. And on the A/C contacts it was mostly contact leaner and cloth; barely touched the board with the 400 grit. The Dremel brush I used was not a wire brush but more of a stiff bristle one, only about 3/16" across. It did seem to clean and polish the fixed contacts in the window switch after I had initially hit them with the 400 grit. Did not use on the A/C head. Thanks--Bob

[scottfab]

Never use sand paper. Use a pencil eraser. Not a pen eraser but a pencil eraser. It is an extremely fine rubbing compound. Follow this with liberal amounts of dielectric grease to help seal it off from oxygen. This would be for the ribbon connector strip NOT the buttons.

[WARP TEN]

Originally Posted by Dynomite

Anyone have a nice photo of the Window Switch Panel and the A/C Control Head for the record?

Hey Dynomite---Looks like you might want to edit your excellent summary of what I had written for Scott and Franke's comment about sandpaper. I think Scott is right about using a pencil eraser rather than fine wet/dry paper on the circuit board where the A/C buttons push against the board. On other electrical contacts (think old car ignitions or Lionel trains) I have used very fine wet/drywihtout incident as well as an ignition file but I think Franke is right that if you can access the contacts you are cleaning with a fine metal file that is probably best. But as I noted the fixed contacts in the widow switch are recessed and hard to get at with a file. At least with the ignition file I have. --Bob

[Dynomite]

Originally Posted by WARP TEN

Hey Dynomite---Looks like you might want to edit your excellent summary of what I had written for Scott and Franke's comment about sandpaper. I think Scott is right about using a pencil eraser rather than fine wet/dry paper on the circuit board where the A/C buttons push against the board. On other electrical contacts (think old car ignitions or Lionel trains) I have used very fine wet/drywihtout incident as well as an ignition file but I think Franke is right that if you can access the contacts you are cleaning with a fine metal file that is probably best. But as I noted the fixed contacts in the widow switch are recessed and hard to get at with a file. At least with the ignition file I have. --Bob

Edited for ya.....
As Franke and Scottfab suggest, the best method to clean electrical contacts would be with the use of a contact file or a pencil eraser. Not a pen eraser but a pencil eraser. It is an extremely fine rubbing compound.

An Excellent step by step write up...appreciate it
Now for the two photos
I will go out and get em now.....
OOPS......I have a 91' and you a 95' ......is your step by step different for a 95' ?

[WARP TEN]

Originally Posted by Dynomite

Edited for ya.....
As Franke and Scottfab suggest, the best method to clean electrical contacts would be with the use of a contact file or a pencil eraser. Not a pen eraser but a pencil eraser. It is an extremely fine rubbing compound.

An Excellent step by step write up...appreciate it
Now for the two photos
I will go out and get em now.....
OOPS......I have a 91' and you a 95' ......is your step by step different for a 95' ?

My 95 looks the same as your pictures except for color. The two screws to remove the window switch trim plate are visible in your shot, and the A/C head looks the same. You can just see two of the four small hex screws that you need to remove to get the A/C control head apart. There are also two small hex screws inside that hold the circuit board to the switch plate. ---Bob