1968 CDV Climate Control...no heat.

[Blu68caddy]

I had many problems with my  Automatic Temperature Control (ATC) as well on my 68 DeVille Convirtible
I purchased a manual from "Cadillac Tim" and with a vacuum gage , volt meter and very few tools I got mine working like new again.
Check out his website    http://cadillactim.com/index.html
It is invaluable informaition

Mark Morris  "Blu68caddy"

[man1ey]

You guys notce that in the shop manuals there are all kinds of "special tools"? In the section on climate control there is a special tool for the temp selector dial....where in the world wouid I get one of THOSE???

Steve, instead of that tool, just use a very very small screwdriver along the left side of the temp selector dial.  Put a piece of tape on both sides to keep from scratching anything.  Slip it in there and hold the toothed wheel while moving the numbered dial.

Keep track of where you started in your head so you can make corrections or return it to where you started.  I found mine to be off by about 10 degrees and adjusting it (once the rest of the system was working) made a nice difference.

Mike

[Steve W]

More info please Mike...would that strip anything? So the dial moves the toothed wheel? And the toothed wheel is what sets the actual temp?

[STDog]

No, the dial turns a variable resistor. It's not firmly attached though, and by holding the toothed whel you can turn the dial without turning the resistor shaft. That's for calibrating the system.

As Mike mentioned it can be out of adjustment quite a lot, especially as the sensors age.

So, you have the dial at 85 but the system thinks it's at 75.


Follow the adjustment procedure in the manual.

[man1ey]

More info please Mike...would that strip anything? So the dial moves the toothed wheel? And the toothed wheel is what sets the actual temp?

SteveW, grab a flashlight and look down the left side of the wheel... you'll see teeth.  Those teeth and the indicator dial are on the same variable resistor STDog mentioned, but they're not attached to each other - the indicator dial will slip while you hold the toothed wheel in place.  

STDog, or others, I melted the in-car thermistor (i.e. the sensor) by accidentally grounding a wire going to the amplifier.  Those resistors can't be soldered back together apparently, as the disk is ceramic and solder won't hold.  Any idea where I can pick up a replacement?  I'm going to see if Cadillac Tim has one but would prefer a new one.

BTW don't ground that wire like I did - the green one on the amplifier.  That ceramic disk de-soldered itself, fell right out of the sensor duct, landed on my neck, and left a nice, perfectly round burn.

[STDog]

Should be a common enough thermosistor. The trick is getting the right temperature/resistance range.
I think the shop manual has the specs for them.

I'd be searching Digi-Key, Mouser, Newark for a replacement

[man1ey]

Should be a common enough thermosistor. The trick is getting the right temperature/resistance range.
I think the shop manual has the specs for them.

I'd be searching Digi-Key, Mouser, Newark for a replacement

Sure enough - I've been at Mouser and found one I think will work tho I can't find the R-T curve to be sure.  It's correct at 25c but I'm not an electronics expert so I'm slow figuring out whether it will work at other temps for me.

Using the R-T curve Glen posted previously to compare to.  Thanks both for your posts so far.

[STDog]

Sure enough - I've been at Mouser and found one I think will work tho I can't find the R-T curve to be sure.  It's correct at 25c but I'm not an electronics expert so I'm slow figuring out whether it will work at other temps for me.

Using the R-T curve Glen posted previously to compare to.  Thanks both for your posts so far.

What the part number Mouser lists? Where the cure you're trying to match?

I haven't used Mouser much, but Newark and Digi-Key usually have good spec sheets.

Just takes some time to learn to read the datasheets.

[Steve W]

That did it!!! Thanks guys!
Just like you said, I went to the left side of the dial with a small screwdriver and was able to turn the dial to increase the temperature. In fact, I turned it up a little TOO much at first, but going through all the temp ranges, I have it dialed in pretty good now! And now, when its on, say, 85, the heat comes thru the floor vents too, which it didn't before!

Thanks again!

[man1ey]

What the part number Mouser lists? Where the cure you're trying to match?

I haven't used Mouser much, but Newark and Digi-Key usually have good spec sheets.

Just takes some time to learn to read the datasheets.

STDog, I ordered Mouser 527-3504-50.  It was a lot of footwork but now I'm certain it's the right part.  The resistance-temp curve matched the owner's manual exactly at 0c, 25c, and 40c.  The dimensions are identical as well.

To others, I recommend Cadillac Tim's guidance on repairing these systems.  He's a lot easier to understand than the manual, which relies heavily on the use of the old dealer diagnostic stations. He has lots of used and reconditioned, tested parts.  I have ordered parts from him in the past it's always a good experience.  If my cheapskate fix above doesn't work, I'm going to buy the part from him.

[STDog]

STDog, I ordered Mouser 527-3504-50.  It was a lot of footwork but now I'm certain it's the right part.  The resistance-temp curve matched the owner's manual exactly at 0c, 25c, and 40c.  The dimensions are identical as well.

I'm confident you got the right part and it''ll work. Handy info for the future as the supply of old parts is diminishing and used parts my be out of spec due to age.

[Mike GA]

STDog, I ordered Mouser 527-3504-50.  It was a lot of footwork but now I'm certain it's the right part.  The resistance-temp curve matched the owner's manual exactly at 0c, 25c, and 40c.  The dimensions are identical as well.

Well Mouser had 2 thermistors (sensors) in stock.  I ordered both of them.  They shipped me the wrong part and sent my thermistors to someone else.  Now they're out of stock.

Digikey and Mouser can both get them but they won't quote me a time.  And get this - they asked me to return the incorrect part to them at my expense.  I told them they weren't getting it and they changed their mind and sent me a UPS label.

I could use an angrier smiley right about now...

[STDog]

Digikey and Mouser can both get them but they won't quote me a time. 

As I said, I've never dealt with Mouser.

DigiKey has always been quick to ship and arrive, though it's been a few years since I ordered from them.

Newark was always quick, and I lived near a warehouse, so it arrived quick too.

[Mike GA]

Newark was always quick, and I lived near a warehouse, so it arrived quick too.

I've had good luck with Mouser in the past with some really complicated orders.  I was surprised they messed it up.

Thanks for the Newark lead.  I'll give them a shot too.