'77 AutoTemp II to Manual conversion

[WissaMan]

I recently converted my 77 New Yorker from Auto Temp II to manual controls. It's been done before and there are some threads here already about it, but I figured I'd share my experience as I may've done things a bit differently than others.

First, the lead up to this...

I got my 77 with a non-working Auto Temp system. Actually, it would do some things, occassionally, but never what was asked. But usually it would just do nothing.

I was hoping to get it working, and in fact put considerable time and some money into that. I even went so far as to purchase a testing tool to help troubleshoot. First thing I discovered was the pushbutton control was shot, it wouldn't hold a vacuum at all in any position when I tested it. Knowing that was definitely bad I bought a new one. That one tested perfectly, held a vacuum in all positions indefinitely. I thought I'd put that in and it'd be good to go, but unfortunately not. With the testing unit, I could run it through all the modes. All the doors would open/close properly, fan would adjust, etc. But without the tester, it didn't work. All the sensors tested good so I figured it was a bad amplifier. I was prepared to buy a new one of those (or get mine refurbed) but then I discovered the servo itself had problems. It seemed to move just fine but I could hear a hissing coming from its vicinity. That basically clinched it right there. I was done throwing time and money at it. So onward with the conversion.

 

[traintech55]

My advice is if you can lay your hands on any "C" body, (1974-1978) You can get all the parts you need. Check with the Derby guys out there as these parts are normally removed.

 

[WissaMan]

As I said, I don't plan to do a whole play-by-play here (but feel free to ask me questions and I'll do my best to answer). Rather, I just want to add to what's already out there to help others that want to do this.

First, I purchased a manual button control and a new button-valve thingy from ebay. And made my first mistake.... I bought ones from a 74-75 thinking 74-78 were all the same. Well, they're not. The pins for the compressor switch on/off don't close when the defrost button is pushed in. Only Max AC and AC. I guess 74-75 has another method of activating the compressor when in defrost. But rather than take the hit and buy another one, I added a microswitch onto it to activate the compressor when the Defrost button is pushed in. Not something I wanted to spend time on, but at least it's good to know if a 76-78 unit isn't available, a 74-75 could be made to work with some effort

 

[WissaMan]

Next were the vacuum lines. All you need to do is follow the routing for the manual AC controls in the service manual. The vacuum servos are all the same. I bought new vacuum lines as I didn't want to hack up the vacuum hose harness. I wanted to keep everything as intact as possible. Not that I'd ever switch back, but I figured they might be useful to someone else.

The OD of the vacuum lines is 1/8". But I ran a 3/16" line from the vacuum reservoir to the pushbuttons to give the system a little extra "umph". I used push-to-connect fitings to go from the 3/16" to the 1/8" and also for the one T-connection that is required. I bought a couple different colors of hose to help me keep it organized.

Staying with my desire to not destroy the auto temp parts, I made a 3D printed version of the hose connector. I didn't have to, but I like learning what's possible with 3D printing and what's not. For instance, I learned that normally, 3D prints done on a FDM printer are not air tight. Air can leak through the layer lines, and that happened with mine. The solution is to increase the extrusion rate to really mash the layer lines together. By the 3rd attempt it was holding air (I tested them by submerging under water and pressurizing with the Might-T-Vac.). The material I used, btw is Filamentium FlexFill. After pushing it onto the button nipples, it stays there very firm. How long that springy tension holds up over time remains to be seen, however.

At this point I started the car and tested all the modes and all the servos worked as they should. Hurray!

 

[WissaMan]

Next came the electrical. There is an error in the 77 Chassis and Body manual, which I realized after some amount of head-scratching.

This is from the Chassis and Body manual

This is from the Electrical manual

The difference is the electrical manual shows that the two "out" pins on the pushbutton control are in fact, connected together. And they have to be. If they are not, there will be a condition where there is no fan. The Chassis & Body manual shows them not connected.

edit: actually, now that I look again and reconsider, I think it could be made to work with the upper diagram if it was connected to the resistor a certain way. Maybe that would give slightly different speeds depending on the mode. But the way I did it, I have 4 well distributed fan speeds including very low and max (no resistor) and that's all I need.

 

[WissaMan]

The one part I did re-use was the fan resistor assembly. It has some extra tabs because the Auto Temp has I think 6 speeds. I just picked ones that gave me a good range of speed from low to high.

For the fan connection, I just plugged into the 4-pin connector in the car. Same for the compressor wire.

For the power feed into the switch assembly, I hoped I could find plugs in the existing harness to plug them into, but I could not. They may be buried somewhere in the dash or maybe if a car has AutoTemp they just aren't there. So I spliced into the wires at the fusebox, connecting to the correct fuses as indicated by the electrical manual.

 

[WissaMan]

With the servo unit removed, there is a big opening in the "package".

I made a cover on the 3d printer, because that's easier for me, but a piece of sheet metal or whatever would work fine too. I used some 3M two-sided squishy tape to adhere it. I also covered the hole left over from the ambient temp sensor.

 

[WissaMan]

Next the connection for the cool/heat blend door. This was actually probably the most frustrating part for me because it involved lots of test fitting and working in a tight spot under the defrost vents. FYI, if you take the 4 screws out of the vents, they will lift up and give an extra inch or two of room to work.

My pushbutton assembly I bought didn't come with the cable. (I actually kind of forgot about the cable until I was pretty far along with this). So I bought a choke cable off Amazon and cut it to the size I needed.

The Auto Temp works the actuator backwards from the manual control, so if you just hook the cable up to what's left after removing the servo, your heat/cold will be backwards (yep, found that out the hard way). But, the lever that connects to the door pivot can be reversed. I ground off the pin that held on the articulated extension and put a screw through the hole that was left to hold onto the loop I made at the end of the cable. I made the bracket that's holding the cable in place and adhered that with that same 3M double-sided tape. That stuff sticks very firmly, but I hope it holds long term. It was too tight in there for me to hold it down with screws.

 

[WissaMan]

Well that's it. Everything seems to work right except I don't notice too much difference in the air velocity coming from the heat and defrost vents when switching between heat and defrost. The servo does move, because I can see it moving. I don't know if that's to be expected. I know it is supposed to "bleed" somewhat but to me it seems like there's more than I would expect.

 

[75LandYacht]

I’m excited for your progress Jesse.. Ginger is getting the attention she deserves…

 

[WissaMan]

It's all interior stuff for now and without a heated garage the work will slow over winter :0

If all goes according to plan I'll start the metal work in the spring.

 

[3175375]

You may need to adjust the defrost / heat door (linkage?). If the box for your car is similar to a 69 box, I believe that there’s a linkage adjustment procedure.

 

[WissaMan]

That is a good suggestion. I looked all through the 77 FSM though and didn't see any reference to that sort of adjustment, except with the heat-only unit that has the slider to move the heat/defrost door.

 

[WissaMan]

Got a chance to take a look at the heat/defrost door linkage tonight and found that the vacuum servo was disconnected from the lever. Apparently someone must've worked on it in the past snapped the clip onto the lever before attaching the servo rod so it wasn't actually holding the rod to the lever. And as I was reaching up there to connect the vacuum hoses I must've bumped it and knocked it off the lever.

It was a pain to get it back on there correctly as you can only get one hand up there to do it and that clip is sharp and I sliced my finger on it in the process, but now it all works as it should -- 100% floor when Heat is selected, defrost and some floor when Defrost is selected...