Rotary HVAC control to fix bad ATC

[GM_Guy]

If you are doing a rotary control swap, or anything swap for that matter, (assuming there is an arm of the same style), it won't matter that the direction of travel is opposite on an atc car. Hot on the dial = cold, cold on the dial = hot. The dial don't care.
Hard to believe its been more than 10 years since I did that rotary control swap.

[kishy]

Well, I mean...yeah. It won't matter because you're in there hacking it up regardless. Push, pull, whatever.

Where it gets tricky is,
-mounting the cable (keeping in mind you can't put fasteners into the HVAC plenum or you'll block the blend door),
-the cable being long enough to reach all the way around if indeed its direction needs to be reversed,
-the cable having enough throw to actually operate the blend door through its whole range of motion

This isn't a combination of parts the factory ever assembled, so there is no guarantee it works until someone gets in there and tries it. There is surely a reason why the ATC and manual climate control cars have the differences that they have.

Don't mistake me for discouraging the model year mix-n-match. I'm a big proponent of bastardizing what the factory gave us. I just think if someone wants to dig into this they need to realize there's a good chance it isn't remotely plug & play.

[Arquemann]

On this video, it looks like the manual blend door cable is quite long

https://www.youtube.com/watch?v=ntQFNqbLIpo

Looks like the throw on the blend door isn't too long, arm radius of maybe an inch or 1,5 and it travels way under 90 degrees.
I dug out pics of Lutrova's ATC plenum and there's plenty of brackets for the vacuum blend door actuator to use for mounting a cable.

All I'm thinking about is converting ATC temp control to manual, nothing else. Obviously a full manual conversion would include no bastardizing, but it's a shitton of work and for me parts availability is between none and zero.

HVAC is ass, no wonder some people throw a couple grand at Vintage Air & Restomod Air kits. And still get shafted on automatic temp control and fresh air.

[gadget73]

86VickyLX has EATC in his 86 using a 90s climate control. The original air plenum was modified to take the blend door servo. It apparently works fine, though visually its quite obviously not 1980s original since there is a digital thing in the middle of the dash instead of the old slidey bar controls.

If mine ever decides to nope out and my supply of junkyard sensors dries up, I'll just modify the crank arm on the blend door and run a cable from the temperature slider to the door. Can't be all that complicated. Bracket to mount the cable and maybe change the length of the crank arm so it matches the cable throw if needed.

[DerekTheGreat]

My sensor is starting to fuck off. I replaced it seven years ago with a Motorcrap one from 2001, IIRC. Meh. Didn't a dude make a thread on how to refurb the sensor? Thought that turned out pretty well for the guy?

[friskyfrankie]

Anybody verify the link I posted?

[Arquemann]

Anybody verify the link I posted?

I've seen that exact same page a year or two ago. Probably not actual stock.

[friskyfrankie]

I've seen that exact same page a year or two ago. Probably not actual stock.

Could be. If someone needs it, they should at least see if it is a live listing and really in stock. Possible it is just sitting there since there may not be a great demand.

[gadget73]

I found someone that had a couple at Carlisle years ago. Obviously very old boxes, I think early 90s date codes. He wanted 100 each. He kept them at that price too. sort of curious how many people even knew what they were or had any interest in them. 80s car stuff is not exactly a hot seller at those kinds of things.

[DerekTheGreat]

Right.. If I got about seven years out of a piece from the early 2000's, I'd bet the 90's unit is dead in the box, no?

[Lutrova]

Didn't a dude make a thread on how to refurb the sensor? Thought that turned out pretty well for the guy?

I linked to that thread in post 8 here. Hillbillycat started down the route of ultrasonic cleaning, but ultimately we found an internal retainer breaks down and can allow the needle valve to wander. Eventually it will slide totally out of place and allow full vacuum to pass through, creating the no heat condition. Careful disassembly of the sensor and insertion of a new retainer should restore proper function - or at least that's my working theory. I've had decent results with my fix so far.

[kishy]

I linked to that thread in post 8 here. Hillbillycat started down the route of ultrasonic cleaning, but ultimately we found an internal retainer breaks down and can allow the needle valve to wander. Eventually it will slide totally out of place and allow full vacuum to pass through, creating the no heat condition. Careful disassembly of the sensor and insertion of a new retainer should restore proper function - or at least that's my working theory. I've had decent results with my fix so far.

I've stickied that thread now. I had forgotten about how much progress was made in there...it's a fantastic chunk of information.

So realistically, as a community, we should focus on two avenues to resolve:
1 - hard mode/detail-oriented/keep it original - a consistently repeatable repair for the sensors, and I think you're on the right track with how to achieve it.
2 - less original for greater chance of long-term reliability - a consistently repeatable EATC retrofit that can be broken down to steps that the average tinkerer can follow.

Or that's my opinion, at least.

[Kodachrome Wolf]

Right.. If I got about seven years out of a piece from the early 2000's, I'd bet the 90's unit is dead in the box, no?

Figure I'd mention I know TecNickal got two NOS units for his '89, and neither were any good at this point out of the box. Unsure of the date codes though, but I could only imagine they were over 20 years old. Both behaved in the usual failure fashion.

Current plan is to swap to the conventional style system, however. I did forward the ATC thread above to him though. That's wildly informative!

[Lutrova]

I've stickied that thread now....So realistically, as a community, we should focus on two avenues to resolve:
1 - hard mode/detail-oriented/keep it original - a consistently repeatable repair for the sensors, and I think you're on the right track with how to achieve it.
2 - less original for greater chance of long-term reliability - a consistently repeatable EATC retrofit that can be broken down to steps that the average tinkerer can follow.

Or that's my opinion, at least.

Thanks for the sticky. There's plenty of trial and error in that thread. It'd be nice if we could summarize it and other known solutions and make use of the new Articles section of the site, like the tech section of Lincolns Online.

The biggest thing we need now is more people to attempt the sensor repair and report their results. Right now we have a sample size of two. I didn't find opening up the sensor to be very difficult, but it does require more precision than most other things in these cars.

As for an EATC retrofit, it may be the more robust solution - though I believe the ATC sensors should last a long time once repaired - but it won't be too many years before the supply of junkyard Aeros start to dry up.

What would be really cool is if we could cobble together a custom EATC, probably using a raspberry pi or similar. If I had the skill set to do that I'd also make a custom control module for the digi dash message center, one that could incorporate other data like coolant temp or oil pressure. But that's all a pipe dream.

[gadget73]

my single biggest issue with an EATC retrofit is it looks out of place. The stock system is crap but its period-appropriate crap. Would be cool to figure a way to marry it with hidden tech so it actually worked without anyone knowing what was going on. Maybe have the temp lever run a slide pot that works as an input to one of those mini magical computer boxes that people use for everything now. Swap the stock sensor for a thermistor to get an electronic signal input, and use the later BDA to move the blend door and report back where it actually is. Could likely dump the stock fan resistor for the late one to get it fully variable as well in 'auto' mode, and still provide the manual 3 speeds otherwise. Basically a DIY EATC that uses the stock control head as the interface.