Rebuilding the ac/heater control switch

3175375

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Taking a stab at rebuilding the control switch for the ac/heater.

Got it all apart and am going to reassemble today.

I used the Bob Smith Industries Super Glue with accelerator and JB Weld to shore up the corners. Also used the reference in another post here (linking to an A body thread) to drill the rivets and tap the holes for 4-40 threaded pan head screws.
Vacuum ports look good.

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3175375

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That’s exactly what I am using as a reference. The switch that I am rebuilding is a bit different than the example, but the way that they are constructed are similar.
My switch has a 4th switch ‘cam’ whereas the example has 3. These are the mica plates with angles cut in them that move the vacuum and electrical switches as the mode buttons are selected. Additionally, they provide the logic and individual switch selections (unselecting the previous switch and engaging the chosen switch) when one pushes one of the buttons.

Thank you for repeating the link - I have a hardcopy and was too lazy to look it up.
 

Big_John

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That’s exactly what I am using as a reference. The switch that I am rebuilding is a bit different than the example, but the way that they are constructed are similar.
My switch has a 4th switch ‘cam’ whereas the example has 3. These are the mica plates with angles cut in them that move the vacuum and electrical switches as the mode buttons are selected. Additionally, they provide the logic and individual switch selections (unselecting the previous switch and engaging the chosen switch) when one pushes one of the buttons.

Thank you for repeating the link - I have a hardcopy and was too lazy to look it up.
The A Body forum has a great tech section with some good "how to" articles. How To Articles | For A Bodies Only Mopar Forum
 

3175375

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Got the mode control switch together and still don’t have a blower running in heat or defrost modes. I do have blower control in AC and Max AC.

I am wondering if there’s a wiring error or something isn’t right in the heater circuit.

I am printing out the section of the service manual on heating and air conditioning (24) and will review.

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thethee

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I'd suggest you also look at your wiring diagrams. Might give some insight into where the blower gets its power from with the different modes. I think the blower is completely separate from the vacuum routing
 

3175375

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I'd suggest you also look at your wiring diagrams. Might give some insight into where the blower gets its power from with the different modes. I think the blower is completely separate from the vacuum routing
Reading the fsm now.
There’s a lot to digest.
Blower doesn’t go in heat or defrost.
 

3175375

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Discovered issue!
Mechanical ‘cams’ aren’t moving the switch on the back of the mode control switch.
Manually moved slider inside the mode control switch and the heater blower works in defrost and heat.
When I switch it to ac, the switch moves to the ac position and when I go back to heat or defrost, the switch doesn’t move back far enough.

Now will have to ‘regrind’ those cams, which are made of mica.

More to come….
 

3175375

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Pulled the ac/heater control switch out of a 68 Fury dash that I got from @Fury Man Van and opened it up and pulled the cams out of the insides.

Good!

Lubed them up and put them in the car and no joy.
I verified continuity on the mode switch.
I will have to trace the wiring from the mode switch to the blower motor resistor as all fan speeds work in the 2 ac modes, but not in heat or defrost.
I’ll chase the brown wire to the blower motor resistor.

Here’s the cams out of the 69 and 68 switch and the schematic.
I am assuming that the blower motor resistor is behind the glovebox. Can someone tell me where it’s located?

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thethee

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Discovered issue!
Mechanical ‘cams’ aren’t moving the switch on the back of the mode control switch.
Manually moved slider inside the mode control switch and the heater blower works in defrost and heat.
When I switch it to ac, the switch moves to the ac position and when I go back to heat or defrost, the switch doesn’t move back far enough.

Now will have to ‘regrind’ those cams, which are made of mica.

More to come….
Doesn't this indicate that the cause of your problem is with the switch and that the wiring is okay?

In a previous pic the switch housing looked broken, could it be that not the cams but the housing is causing the switch to malfunction in some way?

Just thinking out loud
 

3175375

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Doesn't this indicate that the cause of your problem is with the switch and that the wiring is okay?

In a previous pic the switch housing looked broken, could it be that not the cams but the housing is causing the switch to malfunction in some way?

Just thinking out loud
I verified that the electrical portion of the switch was working out of the car with an ohmmeter.
Regardless, a new replacement is supposed to arrive from Jeg’s today.

OER 3895790: AC/Heater Control Switch 1960-1974 Mopar A/B/E-Body - JEGS High Performance

More to come once I get back to the effort tonight or early tomorrow.
 
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sprice

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Not trying to take any credit from Big John's link, all of the tips provided are very helpful. In my case I have one vacuum tube on the car that requires repair. When I read the link, which is fantastic, it occurred to me that I should be able to do the same, perhaps without disassembly. Given its only one and my sense of pressure and steadiness are not what it used to be when I was 20 so I thought I would try on a extra. The rivet idea was the key I have been missing for a year trying to think of how to fix this. With the lip and stem in the rivet for strenght while holding, I threaded the rivet with #8-32 die. It naturally threads lightly as it is close the same size however threads will appear. I then drilled out one of the vacuum ports and tapped with #8-32. Not sure if I used the right bit, hard to see size of die nowadays. I knocked out the stem, then tested with the lip of the rivet for something to grab and turn. Turned out good so ground the lip off, mixed up some JB Plastic Weld (This might not be the best. Plastic/steel cementing is crap shoot or me). Applied the cement material to only the threads of the rivet so not to get into the inside. Screwed the rivet back in with the cement and seems to beholding wonderfully so far. At least since completing this morning. I think using the best cement material would make this 100%. As indicated, not sure the JB is best. Would not have thought of this without all the tips here. Maybe it will help someone. Cheers!

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3175375

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Not trying to take any credit from Big John's link, all of the tips provided are very helpful. In my case I have one vacuum tube on the car that requires repair. When I read the link, which is fantastic, it occurred to me that I should be able to do the same, perhaps without disassembly. Given its only one and my sense of pressure and steadiness are not what it used to be when I was 20 so I thought I would try on a extra. The rivet idea was the key I have been missing for a year trying to think of how to fix this. With the lip and stem in the rivet for strenght while holding, I threaded the rivet with #8-32 die. It naturally threads lightly as it is close the same size however threads will appear. I then drilled out one of the vacuum ports and tapped with #8-32. Not sure if I used the right bit, hard to see size of die nowadays. I knocked out the stem, then tested with the lip of the rivet for something to grab and turn. Turned out good so ground the lip off, mixed up some JB Plastic Weld (This might not be the best. Plastic/steel cementing is crap shoot or me). Applied the cement material to only the threads of the rivet so not to get into the inside. Screwed the rivet back in with the cement and seems to beholding wonderfully so far. At least since completing this morning. I think using the best cement material would make this 100%. As indicated, not sure the JB is best. Would not have thought of this without all the tips here. Maybe it will help someone. Cheers!

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Good work!
Does it work?
The vacuum tits on my control switch are in good shape, so I didn’t have to do these steps.
 

3175375

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Well, I discovered that the connector for the blower motor resistor has gotten hot and melted.
I will replace it. Not sure why the connection is bad for heat/defrost only, but I will get to the bottom of it.
The blower motor resistor is located behind the ash tray mounting bracket and held onto the heater box with 2 1/4” headed screws.
I am going to attempt to remove the blower motor resistor and inspect.
There’s a reason why the connector housing melted and I want to discover it and make the necessary repairs.
My suspicion is that the blower motor resistor is not being used in the heater/defrost position on the mode switch, because it is physically not connected, due to the melted connector housing on the blower motor resistor…
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3175375

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Heater/defrost control now runs blower!

Replaced the connector on the blower motor resistor (stole one from the 68 dash that I bought from @Fury Man Van ), pulled the blower motor resistor and inspected (previous repair ok) and slapped it together outside of their designed locations and the mode control switch now operates the blower in all modes!

I will reassemble and get back to replacing the expansion valve and getting the air conditioning operational.
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david hill

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Well, I discovered that the connector for the blower motor resistor has gotten hot and melted.
I will replace it. Not sure why the connection is bad for heat/defrost only, but I will get to the bottom of it.
The blower motor resistor is located behind the ash tray mounting bracket and held onto the heater box with 2 1/4” headed screws.
I am going to attempt to remove the blower motor resistor and inspect.
There’s a reason why the connector housing melted and I want to discover it and make the necessary repairs.
My suspicion is that the blower motor resistor is not being used in the heater/defrost position on the mode switch, because it is physically not connected, due to the melted connector housing on the blower motor resistor… View attachment 529436 View attachment 529437
The reason why your blower resistor connector melts is due to the fact as it is well known to blower motors on our C bodies and Mopar cars in general are prone to failing especially after many years of use. The problem is of course they draw a lot of excesses amperage prior to failure causing connectors to melt not only at the blower resistor block but sometimes even at the blower speed switch also.
 

3175375

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The reason why your blower resistor connector melts is due to the fact as it is well known to blower motors on our C bodies and Mopar cars in general are prone to failing especially after many years of use. The problem is of course they draw a lot of excesses amperage prior to failure causing connectors to melt not only at the blower resistor block but sometimes even at the blower speed switch also.
Thank you for the reply!

I checked the blower speed switch and it seemed to provide good continuity on all settings.

When I ran the blower, it sounded good.
I suspect that the gent who rebuilt the car put in a good one, or verified that the blower was good enough.
I will monitor the situation and see how it goes.

I know that it’s quite the effort to replace the blower motor on this car as it’s buried….
 

3175375

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Now that I have the A/C running in all modes, except off, I pulled the time delay relay on the firewall and checked it.

I disconnected the time delay relay connections and verified that the AC compressor clutch is not engaged.

There’s no vacuum source hose to it, so it’s always making a connection.

I now need to remove the glovebox and look at the recirculating/fresh actuator as the source of vacuum for the time delay relay is from that circuit. There’s supposed to be a tee on the one side of the actuator (comes out of port #3, activated in ac, heat and defrost on the mode switch - port #1 is connected to the other side of the recirculate/fresh air actuator, activated in Max AC mode. I will have to verify this is plumbed correctly too).

I looked for a vacuum hose in the engine bay - no joy.

I keep thinking about the dude that put this car together and it’s not rainbows, hugs and high fives…
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