70 Cdv Auto Climate Control
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  • 1 Post By 70eldo
The Classic Cadillac Forum Discussion, 70 Cdv Auto Climate Control in Past Cadillac Vehicle Discussion; I am looking for someone/some website,etc who knows about these old climate control systems. They seem to be an ongoing ...
  1. #1
    Jeff R's Avatar
    Jeff R is offline Cadillac Owners Fanatic
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    70 Cdv Auto Climate Control

    I am looking for someone/some website,etc who knows about these old climate control systems. They seem to be an ongoing source of frustration but I have not found a good source for help. Here is my problem (for now) and would love some help but really need a good place to go for troubleshooting. Obviously I will be wanting the heat t work in a few months.

    We have had this 70 Coupe Deville for a couple of months now and have been up/down the manuals but have not had much luck finding my problem. The manuals speak to problems with the blower speed relay and/or selector head issues but I do not think those are my problems.

    I believe I have 2 separate issues--1 with the blower and the other with the heat/temp selector. As it is summer, I have not done much with the temp selector issue--I want a good strong blower at least for now.

    The a/c works well and is cold. The system puts the flow to the dash vents as required. When I turn the temp selector up to 85 there is no change however it has been quite warm here so the cabin has not really been cool. I believe the position selector on the dash works well- I hear vacuum releases when I move the selector. The blower works on low speed in vent, off and Auto Low which I believe is per the system design. When I move the selector to the middle Auto position the blower increases to what I think would be speed 2. When I put the selector in high, the blower increases again but perhaps to speed 3, not to full power. When move it to fog it goes down to the same speed as auto which I believe is also correct and when in Ice it goes to the same speed as Hi which again I would believe is only speed 3. Once the blower went to the full hi position when the selector was in Hi but that is the only time it has happened. I removed the electrical connection from the power module and jumped what I believe are wires 18y and 12t I get a nice hi blower so I do not believe there is a bower electrical problem--I think it is in the power module. I have read that there is a dedicated circuit for the hi positions but it appears to not engage other than the 1 time. I have cleaned the wipers on the power module but I really don't know how to check it. The blower relay does work and I hear it click when it is turned off the low positions.

    So, where should I go from here? Is there a good troubleshooting guide I can use to determine what my next step is?
    Jeff

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  3. #2
    70eldo's Avatar
    70eldo is offline Cadillac Owners Connoisseur
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    Re: 70 Cdv Auto Climate Control

    cadillactim.com may be able to help you out!
    CADforce69 likes this.

  4. #3
    klinebau is offline Cadillac Owners Member
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    Re: 70 Cdv Auto Climate Control

    The operation of the climate control system is detailed in the service manual, but I agree it is very complicated. Based on your description of the problem, I believe that you need to look at the power servo. Make sure that the vacuum hoses that connect to it are routed correctly. Also, check the diaphragm (cylindrical part) and hoses for leaks.

    When in auto mode, the blower speed is supposed to be determined by the difference between the temperature selector and the temp sensor (opening on top of dash over the gauges). A signal is sent to the power servo (via vacuum) to move the lever in and out for the blend (temperature) door. When you adjust the temperature control, you should be able to watch the power servo lever move in the engine compartment by the firewall. The resistors for the fan speed are also in the power servo. I don't remember all of the specifics, but I believe that the lever in the servo has the connectors which control the fan speed.

    I had several problems when trying to get mine to work. First, there was a bad ground for the fan relay. Second, the engine temp sensor wire was not connected to the sensor (this is needed for heat). This wire should be grounded if you no longer have the sensor or if the sensor is broken. Third, the vacuum lines on the power servo were hooked up incorrectly.

  5. #4
    disturbio's Avatar
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    Re: 70 Cdv Auto Climate Control

    another issue could be the temp sensor is on top of the dash, you gotta dash mat? Mine only works when I flip it to 65 and let it run, ac guy told me I needed to cut out a slot in dashmat but im in az, its always hot and i dont want to screw up dashmat for something I will rarely rely on. just a thought.

  6. #5
    Jeff R's Avatar
    Jeff R is offline Cadillac Owners Fanatic
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    Re: 70 Cdv Auto Climate Control

    The diaphram does work and holds vacuum (I hooked a line up to it) and when it moved it did move the blend door arm (however it did not do it automatically). I'll check that the vac lines are hooked up correctly. No telling what was done with the hoses years ago.

    ----------

    Looks like we were on at the same time.....No, No dash mat. It has been warm just about every day we have had the car so I have not had a chance to do much. However there was one cool morning and I turned the selector up to 85.... no change. I have read that the temp sensor, when it dies, defaults to 'warm' meaning that it would go to max cool. Mine does not go to max cool--The servo acts as if it is dead.

  7. #6
    disturbio's Avatar
    disturbio is offline Cadillac Owners Fanatic
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    Re: 70 Cdv Auto Climate Control

    What is the lil vent with a switch on the front of sash passenger side do?

  8. #7
    70eldo's Avatar
    70eldo is offline Cadillac Owners Connoisseur
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    Re: 70 Cdv Auto Climate Control

    Quote Originally Posted by disturbio View Post
    What is the lil vent with a switch on the front of sash passenger side do?
    That's the map light. Check the bulb

  9. #8
    talismandave's Avatar
    talismandave is online now Cadillac Owners Master
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    Re: 70 Cdv Auto Climate Control

    No wonder no air comes out of it!

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