[margozzi]

Hello everyone, I am offering repair services for ATC (Automatic Temperature Control) units on mid 60's to 70's Pontiac's. I spent the time to figure out how the entire system works and can get your ATC module working as is should. I also test the entire functionality of the ATC's vacuum switch, control over the fan, calibrate the temp sensor inputs, etc.

I live near San Jose CA, so you will need to ship the unit to me.

The cost depends on whats wrong with it, however a baseline charge is ~ $200 + shipping out and back.

Please contact me if you have questions, I'm also happy to help you debug the ATC system before you pull the module and ship it.

Thank You!

Paul Margozzi
(408) 888-4374

[stevep]

Can you repair the power servo on mid 60's cars?

[margozzi]

Steve, can you send a picture of the power servo, thanks, Paul

[Mark66]

Paul:

You must be one of less than a handful of people who has taken the time to fully understand the workings of GM’s 60's and 70"s ATC systems. I for one am glad you did!

I have a 1966 Pontiac Bonneville Brougham that has an ATC system – currently inoperable. It is interesting to note that the DAFT Tool 1972 “Automatic Temperature Control Service Manual” did not include the 1965-1970 Pontiac ATC system. With reference to these particular years of Pontiac ATC’s, the DAFT books says “Total production of these [Pontiac] systems did not exceed 2% of the cars built in any one model year. Because of the small number of cars involved, descriptions and servicing of these systems has been omitted”. So it seems that 1965 to 1970 big Pontiac buyers did not see value in upgrading from the Custom Air Conditioner option (in 1966 a base price of $421.28) to the Automatic Temperature Control Air Conditioning option (in 1966 a further additional base cost of $63.19).
I have found, at least for 1966, the Pontiac Air Conditioning Shop Manual and Pontiac Craftsman News provide quite a bit of useful support information. And Pontiac also published a stand-along “Pontiac Automatic Temperature Control – 1965-1966 – Servicing and Repairing, Model with Auto Temp” manual. And there is probably some training literature of which I am not aware.

And there are a couple of diagnostic testers that were released (after 1966) that can, it appears, be used to help identify problems with the 1966 Pontiac ATC system (and later GM - and non GM - ATC systems). These include the Robinair/Kent Moore J-23678 “Electro-Vacuum Programmer – Automatic Temperature Control Tester” and the surprisingly sophisticated looking “GM Programmer Bench Test Universal Analyzer II for Automatic Temperature Control Systems”. The GM Programmer does not seem to have a Kent Moore number and may have been developed and released directly by GM. These two units are readily available on Ebay – a 3rd test unit, Kent Moore J-22684 (Automatic Temperature Control Tester), released in 1967 for, it seems, only Pontiacs, is more difficult to find.
One headache I am running into is locating - and fixing - the various vacuum links in the many, many hoses that are used in this unit – what a pain. Crawling under the dash to de-bug vacuum leaks is for the young and thin only. For instance, It would seem take a Wallenda family member to connect the vacuum multi-hose coupler to the ATC control unit while in the car.

So I applaud your efforts to understand and repair these systems. You may see some of my components in the future.

[margozzi]

Mark,

Thank you so much I appreciate the kind words. Yeah, I put in a crazy amount of time figuring out the entire system, not just the ATC programmer (module)... but I had fun and I hope that I can help anyone with a limping ATC. If you are interested please let me know, I'd love to get your system going again. I did come across (and now own) a Robin Air test system, but I have to say its rather crude in what it can test for. I have also developed a document that can be used to debug the system and shows exactly how the module works and how to fix it.

Thank you for reaching out to me, if you would be so kind as to send a pic of the 66 ATC that would be great. The picture of the ATC I'm most familiar with was pictured in my ad... maybe the 66 is the same?

Thanks so much,
Paul

[Goatracer1]

I worked for a Pontiac dealer back in the day. We had a used 1975(?) Grand Prix with ATC that we couldn't fix after weeks working on it. It was finally sent to the local Caddy dealer hoping their experience would allow them to fix it. After 6 weeks they sent it back to us. They said that they couldn't fix it either but they did bill us for their time trying.

[margozzi]

Mark,

I also wanted to thank you for the historical info on the production numbers for the ATC, I always wondered about that. I assumed it was low, but after having fixed a bunch of these it seems that they are everywhere ;-) Even at 2% of the 1969 GP production that's over 2000 ATC's. I was not aware of the “Pontiac Automatic Temperature Control – 1965-1966 – Servicing and Repairing, Model with Auto Temp” manual you noted...I'll have to see if I can find that.

I'm not surprised that the Caddy dealer gave up and billed your dealership anyway for the 75 GP ATC. If you have an ATC car its hard to not fix it because it controls everything for the ventilation system. And, depending on what position it decides to stop working the heat could be on wide open or some other random setting that you may not want at any point in time. I see people just disconect the arm and push the door one way or the other, but you still have no control over the vents or the fan.

If you are inclined get a hold of me and we can check the ATC out... I know what you mean about the vacuum lines, there are a lot of them, luckily they are usually ok, the double sided pods are what usually give out, the singles are fine since they don't have the rolling grommet that gives out.

Enjoy your Bonneville Brougham.

Attached is a pic of my 69 GP with ATC.

Thanks, Paul

[Mark66]

:Paul:

Send me a PM with your email address and I will send you a PDF of the ATC manual. It only applies to 1965 and 1966 big Pontiacs but should interest you.

From a diagnostic perspective the 1965 and 1966 Pontiac ATC units are virtually identical although changes were made mid year in 1965 to some ATC components and many part numbers between the two years are not the same (although they look identical). 1965 big Pontiacs also had an ATC temperature sensor in the instrument panel dash pad while 1966 big Pontiacs had it under (and not part of) the dash pad.

Always interesting trying to debug older technology.

Mark

[koestjoe]

Hello Paul and Mark,

Thanks for the very interesting post from you about the ATC.
My name is joerg and i´m from germany.
For 3 months I have been a proud owner of a 66 Bonneville.
I would like to get my automatic temperature air conditioning from the car working again.
The first problem is a big problem. I need the transducer for the vacuum signal for the power servo unit.
I think the spare part number is "GM # 7290912"
This is located at the bottom right behind a panel in the driver's compartment near the air inlet flaps.

Unfortunately, I don't have a original photo of this transducer because it was removed.
Could you help me where i can buy this spare part?

Sorry for my bad language and thanks for your help

Joerg Koester

[margozzi]

Joerg,

Congrats on your 66 Bonneville :-)

You can buy a refurbished vacuum transducer from Caddy Daddy, since you don't have one to use as a core they will charge you extra. The Power servo will most likely have a leak... you will need to test it. There are a couple ways to do it. The Power servo operates on 5 to 7 inch of vacuum max, this is the level of vacuum you need to test with. If you use a higher vacuum you will not detect the leak (if there is one). Reason being the higher vacuum will over ride the leak making you think the power servo is ok. You can also do a simple leak down test, pull a vacuum and seal it off....watch to see if it cant hold a vacuum. Caddy Daddy also refurbishes the power servo... but the actual vacuum pod looks different - fyi.

https://www.caddydaddy.com/

Hopefully the amplifier you have works :-) These can be fixed as well.

Good luck, please post a pic of you Bonneville

Paul

[koestjoe]

Hi Paul,
Thank you for the quick reply.
If I understood you correctly, I can also use a transducer from a Caddilac.
Great. That helps me a lot.

Hopefully the amplifier you have works :-) These can be fixed as well.
That could be the next problem.
On a normal summer day, I measure a supply voltage of about 10.5 - 11V at the supply line to the Trancducer.
Can that be possible or is it too high? I have read that the variable voltage should be between 0 and 9V.
(zero volts for maximum heating to 9 volt for maximal cooling)

Here a picture from my bonneville. A pontiac is very rare in Germany. There are very few of them. you get photographed very often :-)

[koestjoe]

Hello paul.
Thank you very much for your quick reply.
If I understand you correctly then can I use the transducer from a Caddilac?
Great. Then I will order one from there. :-)

Hopefully the amplifier you have works :-) These can be fixed as well.
That may be the next problem.
On a normal summer day I measure a voltage of 10.5 - 11V on the supply line from the amplifier to the missing transducer.
Isn't that too much? I read in the "Pontiac Air Conditioning Shop Manuel" that the voltage should be between 0 - 9V
( 0Volt for maximum heating and 9V for maximum cooling )
Could the amplifier also have a technical problem?

A Pontiac is very rare in Germany and with a Bonneville you get a lot of attention :-)
Here is a photo of my Bonneville.
Many greetings, Joerg

[margozzi]

When you contact Caddy Daddy make sure you tell them its for your Bonneville, but I believe that they are the same part.

When you measure the output of the amplifier it needs to be under load, meaning that transducer is connected. You can substitute a 36 Ohm resistor to do a quick test, which out the load the amplifier will not operate properly. Yes, 0-9V is what you want to see.

Super nice Bonneville, man I forgot how long they are :-) You may have the only one in Germany ha ha!!! Get that baby out on the Autobahn and open her up!

I have a document you may like to have to help debug your ATC, I put it together as I was learning about the 65-66 ATC, PM me with your email and I'll send you a copy. I have fixed a bunch of the 67-72 ATC, that's the main years I work with.

[koestjoe]

Hello Paul,
Thank you very much for the offer to send me the documents.
I'll send you am PM
This will help me a lot. It's winter soon and then I'll be working on the air conditioning.

Yes, our highway (Autobahn) is great.
I live in the north of Germany and there aren't that many speed limits here. The new cars make it easy to drive 185 mph when there is no traffic :-)

Many greetings from Germany

[Mark66]

Joerg:

Sorry for the delay in reply to your transducer question. A couple of points for you to consider:

1) The Cadillac picture of the transducer sold by CaddyDaddy looks identical to the unit used by Pontiac B bodies in 1966 (and 1965).

2) The transducer part number you reference, 7290912, is correct for 1965 and 1966 big Pontiacs. The three part numbers referenced by CaddyDaddy in their description of the transducer they sell do not match the Pontiac part number although one is close (7291913). The fact that the part numbers are different does not necessarily mean that the units are different. If you do order the CaddyDaddy unit I would be interested to hear if it works on your car.

3) I have a used transducer from a 1966 Pontiac Bonneville. It has been in dry storage for 20+ years but I have never checked to see if it works - if you strike out everywhere else let me know.

4) Pontiac published a stand-along ATC servicing and repairing guide - I think it is pretty much a repeat of what is in the Pontiac AC service manual but perhaps with some updated diagnostic testing procedures. If you send me a PM with your email address I will send you a pdf of it.

Good luck rejuvenating your ATC system - I will soon start (trying to) rejuvenating mine.

Mark

[koestjoe]

Hello Mark,
Thank you very much for your answer too.

Pontiac published a stand-along ATC servicing and repairing guide - I think it is pretty much a repeat of what is in the Pontiac AC service manual but perhaps with some updated diagnostic testing procedures. If you send me a PM with your email address I will send you a pdf of it.

Thank you very much for your offer, I will do that and send a PM.
I also received a document from Paul that is very professional and also helps a lot.
I ordered a transducer from CaddyDaddy. He thinks this will also work on a Pontiac.
The transducer will be delivered in two weeks. I'll let you know if it works.

Many greetings,
Joerg

[70L34]

Hello - I'm restoring a 1971 Chevrolet Comfortron system. Are you offering any rebuild or calibration services on these systems? Thanks!