Electrical gremlin

[dan juhasz]

I replaced the ac vacuum control push button switch in my 67 gtx. The nos mopar switch I used has different applications depending where you read. The only difference I saw was one one side of the switch where it has 3 termin also very close to each other. On the original all 3 were seperate ( however only 2 get used) on the new switch 2 of the 3 are bridged together. Even in my 67 service manual ( repop) I can't find a diagram that show's the original switch. Anyway problem is the compressor clutch is receiving voltage in all positions ( including off) with the exception of the heat position. Heat disengages the compressor. But the compressor runs in off, not good. Ant ideas, I think I need the original switch that is not reproduced.

 

[Bill Monk]

I don't know what the original switch looks like but I found this. Hope it helps.
https://www.carid.com/oer/hvac-control-switch-mpn-3895790.html?singleid=229449688&url=17956454

 

[Bill Monk]

Found this too if you have your original switch
https://originalair.com/service-custom-control-rebuild-manual-exc-atc-3

 

[Nacho-RT74]

Once I dissasembled couple of those switches with diff pn and even both look exteriorlly the same, electrically were slightly diff. The contact plates inside got couple of differences. Can't describe the difference but they were. For what I saw it seemed something like you described could happen.

This confirmed the PN is there for a reason and NOT every switch is the same even looking exactly the same. Must take care of that and be sure about the superseded sequence number to the original PN for your car.

Can't talk about the vacuum section thought

 

[dan juhasz]

Once I dissasembled couple of those switches with diff pn and even both look exteriorlly the same, electrically were slightly diff. The contact plates inside got couple of differences. Can't describe the difference but they were. For what I saw it seemed something like you described could happen.

This confirmed the PN is there for a reason and NOT every switch is the same even looking exactly the same. Must take care of that and be sure about the superseded sequence number to the original PN for your car.

Can't talk about the vacuum section thought

I always am suspicious when one superceded part number covers a group of years. Until I can source a correct one and because it is such a nightmare to remove and replace any component under that dash I removed the 12v feed green wire and the compressor feed blue wire and ran them through an illuminated toggle switch under the dash.

 

[Nacho-RT74]

It seems those with the deal you are describing are for C bodies. If you have the original PN can get all ( or part ) of the supersedes numbers at mymopar.com on part numbers search.

If not all, some of them that searching again could get you un another row of supersedes numbers.

By what I have found, it seems there are actually just 2 or maybe 3 diff models.

On a note appart, 70s and 80s
Mercedes used same kind of switch.

I have one in hands which I think came from a 70 Coronet with 3502126A pn on it and is quite diff on the middle prongs, being one of them Off,
Not lined up like the ones on OER website.

This is one of the ones I dissasembled. Can't recall where is the other one.

 

[Nacho-RT74]

Here the pics of the inner parts.

The sheets shown are somekind of levers combination able to pull out some of the pushbuttons while some others are kept in place. This combination of baquelite sheets is what makes the function plates pulling and pushing the buttons.

Two of them got also tabs to move the blower lever and vacuum switches attached to rear cover

However I recall a diff also on the metallic sections of the swich ( the pronged ones )

 

[dan juhasz]

Here the pics of the inner parts.

The sheets shown are somekind of levers combination able to pull out some of the pushbuttons while some others are kept in place. This combination of baquelite sheets is what makes the function plates pulling and pushing the buttons.

They two of them got also tabs to move the blower lever and vacuum switches.

However I recall a diff also on the metallic sections of the swich ( the pronged ones )

View attachment 436268 View attachment 436269 View attachment 436270 View attachment 436271 View attachment 436272

That is quite a mechanism inside.

 

[Nacho-RT74]

Forgot one pic.

Pushing for example one of the buttons, slides to lef and right the sheets, pushing out or keeping in place ( depending of the sheets combination ) the rest of buttons.

Is like line up several key cilinders rows in just one piece and having one key for the AC, one for Heater etc...

The buttons include the metallic tabs what close the clutch circuit between both middle prongs if the corresponding function is selected on button.

 

[Nacho-RT74]

if you get the courage, you could open the switch assembly and bend the button tab what keeps the compressor clutch plates circuit closed in the OFF position button.

Dunno if you are able to see what I mean on pic!

Then reattach the rear plate with small selftapping screws ( I did it with success on the other one )