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Discussion Starter #1
......answers to these quests about Auto Temp Control????
_______________________________________________________________________________

1. If vacuum into the cabin from the vacuum tank is CONSTANT, or only on DEMAND? (I have vacuum leaving manifold and going INTO tank, but no vacuum LEAVING tank via black module on top of tank.......moved temp control and mode levers every which way.....still no vacuum leaving vacuum tank)

2. If on DEMAND, then what signals vacuum tank for vacuum demand?

3. If temp control lever or mode lever actuates air mix door?

4. What purpose the vacuum module on the the heater valve serves?

5. If vacuum to the above module is CONSTANT or on DEMAND? If on DEMAND, then what signals for demand (temp ctl lever???.....mode lever????......prayer to Allah????)
_______________________________________________________________________________

Have studied Factory Service Manual.....find it presumes familiarity with auto temp ctl syst operations, and is silent on same operational facets. Would appreciate all helpful responses rather than ....read the service manual.... responses.

Sammy
 

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Discussion Starter #2
> ......answers to these quests about Auto
> Temp Control????
>
> _______________________________________________________________________________

> 1. If vacuum into the cabin from the vacuum
> tank is CONSTANT, or only on DEMAND? (I have
> vacuum leaving manifold and going INTO tank,
> but no vacuum LEAVING tank via black module
> on top of tank.......moved temp control and
> mode levers every which way.....still no
> vacuum leaving vacuum tank)

> 2. If on DEMAND, then what signals vacuum
> tank for vacuum demand?

> 3. If temp control lever or mode lever
> actuates air mix door?

> 4. What purpose the vacuum module on the the
> heater valve serves?

> 5. If vacuum to the above module is CONSTANT
> or on DEMAND? If on DEMAND, then what
> signals for demand (temp ctl
> lever???.....mode lever????......prayer to
> Allah????)
>
> _______________________________________________________________________________

> Have studied Factory Service Manual.....find
> it presumes familiarity with auto temp ctl
> syst operations, and is silent on same
> operational facets. Would appreciate all
> helpful responses rather than ....read
> the service manual.... responses.

> Sammy

I don't know the answer to your question, but I have had some success with getting the heat in my '83 to work. BTW, I do have the auto temp. system too, but my car is not a turbo. So when my heat stopped working I had a vacuum leak in the engine compartment, although I had three different leaks, and I'm not sure which one fixed it, so I'll tell you about all three. You will be extremely lucky if yours is the same problem, but I will tell you nonetheless. Okay, so on the passager side of the engine compartment, near the front, you have the Vacuum tank (aka ASCD Vacuum tank). Two vacuum hoses from the vacuum tank run across the top of the valve cover to the top rear of the intake manifold. Make sure that these hoses are tight. Additionally, there is a hose that runs from the Servo valve (aka, ASCD servo valve) right under the cruise control actuator, which is right in front of the battery. This hose also runs across the top of the valve cover and onto the top of the intake manifold. Fixing these three leaks got the heat working in my car again. BTW, I still am having a problem with adjusting the heat. It seems that either air comes out hot or cold -- nothing just warm. Hope this helps.

kordon
 

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Discussion Starter #3
Sammy-

I sense some frustration so I will try to help with what little I know. The following information comes from studying the wiring diagrams and tracing components on my car, as my auto temp control does not work either.

There are two vacuum lines that run from the vacuum tank into the passenger compartment. One has a red stripe and the other a blue stripe. The one with the blue stripe comes directly from the tank and should have vacuum all the time.

The one with the red stripe attaches to a magnet valve with a black cap. This magnet valve is tripped and vacuum is supplied to the red stripe hose when power is applied to the blue/red stripe wire. There should be power on the blue/red stripe wire when the selector (program) switch is in all positions except off. (I verified this with a test light).

The blue/red striped wire picks up it's power from the switched contact of the blower relay. The blower relay contacts are fed by a yellow wire that starts as a white wire coming directly from the fusible link, and then running to a fuse on the bottom of the blower motor, where it turns into a yellow wire that runs to the blower relay. If this fuse is open, then you get no power to the contacts on the blower relay and no power to the blue/red stripe wire on the magnet valve.

To confuse people like me there is a second blue/red wire connected to the blower relay and this is the one that feeds the blower relay coil from the selector switch.

So the sequence of event appears to be:

1. Place selector switch in any position except off.
2. Power flows through blue/red wire #1 to coil of blower relay and to ground.
3. Blower relay contacts close.
4. Power flows from Battery through fusible link to fuse on bottom of blower to contacts on blower relay and continues on through blue/red wire #2 to magnet switch (with black cap) and to ground.
5. Magnet switch opens vacuum tank to red striped hose and closes to atmosphere.

Well after all that I hope this is helpful!

Bob A.

> ......answers to these quests about Auto
> Temp Control????
>
> _______________________________________________________________________________

> 1. If vacuum into the cabin from the vacuum
> tank is CONSTANT, or only on DEMAND? (I have
> vacuum leaving manifold and going INTO tank,
> but no vacuum LEAVING tank via black module
> on top of tank.......moved temp control and
> mode levers every which way.....still no
> vacuum leaving vacuum tank)

> 2. If on DEMAND, then what signals vacuum
> tank for vacuum demand?

> 3. If temp control lever or mode lever
> actuates air mix door?

> 4. What purpose the vacuum module on the the
> heater valve serves?

> 5. If vacuum to the above module is CONSTANT
> or on DEMAND? If on DEMAND, then what
> signals for demand (temp ctl
> lever???.....mode lever????......prayer to
> Allah????)
>
> _______________________________________________________________________________

> Have studied Factory Service Manual.....find
> it presumes familiarity with auto temp ctl
> syst operations, and is silent on same
> operational facets. Would appreciate all
> helpful responses rather than ....read
> the service manual.... responses.

> Sammy
 

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Discussion Starter #4
The vacuum leak that fixed your problem was the one on the black with white stripe hose that connects directly to the manifold from the vacuum tank. This is the hose that supplies vacuum to the vacuum tank. The other hose that runs across the manifold is a black with yellow stipe hose. This hose supplies vacuum to the Fast Idle Control Device (FICD) and increases the engine speed when the A/C compressor kicks on. it gets it's vacuum from the yellow capped magnet valve on the vacuum tank.

The hose from the Automatic Speed Control Device (ASCD) servo that runs to the manifold has nothing to do with the Heat and A/C but will fix your cruise control.

For whatever it's worth....

Bob A.

> I don't know the answer to your question,
> but I have had some success with getting the
> heat in my '83 to work. BTW, I do have the
> auto temp. system too, but my car is not a
> turbo. So when my heat stopped working I had
> a vacuum leak in the engine compartment,
> although I had three different leaks, and
> I'm not sure which one fixed it, so I'll
> tell you about all three. You will be
> extremely lucky if yours is the same
> problem, but I will tell you nonetheless.
> Okay, so on the passager side of the engine
> compartment, near the front, you have the
> Vacuum tank (aka ASCD Vacuum tank). Two
> vacuum hoses from the vacuum tank run across
> the top of the valve cover to the top rear
> of the intake manifold. Make sure that these
> hoses are tight. Additionally, there is a
> hose that runs from the Servo valve (aka,
> ASCD servo valve) right under the cruise
> control actuator, which is right in front of
> the battery. This hose also runs across the
> top of the valve cover and onto the top of
> the intake manifold. Fixing these three
> leaks got the heat working in my car again.
> BTW, I still am having a problem with
> adjusting the heat. It seems that either air
> comes out hot or cold -- nothing just warm.
> Hope this helps.

> kordon
 

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Discussion Starter #5
> BTW, I still am having a problem with
> adjusting the heat. It seems that either air
> comes out hot or cold -- nothing just warm.

This is a common problem and is the same thing mine does. The reason is that there is a myriad of thingamajigs (TAMAJ) and doohickies (DHKS) that affect how vacuum is applied to the air mix door servo. Any of these fail and you full vacuum.

The system is designed so that with the temp control in the coldest position vacuum is cut off and the air mix door is full cold. In any other position you get full vacuum and full hot on the air mix door.

One of these days I intend to tackle this but have more important things to fix first.

Bob A.
 

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Discussion Starter #6
More Answers

> 2. If on DEMAND, then what signals vacuum
> tank for vacuum demand?

As I described in my other post, moving the mode lever to any position except off puts power on blue/red striped wire to black capped magnet valve and opens red striped hose to vacuum.

> 3. If temp control lever or mode lever
> actuates air mix door?

The air mix door is operated by a servo which gets its vacuum from the transducer. The supply of vacuum for this is through the constant blue stripe hose from the vacuum tank. The transducer gets it's electrical signal from the combined resistance of the temp control lever, the in car sensor and the outside sensor.

> 4. What purpose the vacuum module on the the
> heater valve serves?

It turns the water on and off to the heater core. It is off whenever the temp control lever is set to coldest position and when the mode control lever is set to off or economy. With the mode control lever in any position but off or economy and the temp selector lever in any position but full cold, this valve should be open and allowing water into the heater core.

Hope this is helpful.

Bob A.
'83 280ZX N/A
 

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Discussion Starter #7
MSG FOR BOB A...sincerest thanks...see text...

Not to dismiss all those who've taken the time to answer my questions, as opposed to refer me to service manuals, but.....after a week of questions on the web about my auto temp system I was beginning to wonder if anyone really knew the sequence of operations of the auto temp system. And so, your intuition about my frustration was right on target. Freezing my toes off on the daily 56 mile round trip to work didn't contribute to a 'positive attitude' either! Now, after reading your response, I can't tell you how happy I am to have the answers I've been seeking

Your explanation of the magnet valve purpose, and it's electrical operation is absolutely outstanding. It was not knowing these things that prevented me from accurately diagnosing the problem(s), and drove me nuts. With your information I feel confident and look forward to testing the vac/elec/valve operations this weekend. I only wish I could start work on it right now. But, as they say, ...there's a time for every purpose under heaven....

I'll be sure to let you know how I make out. Until then, please accept my sincerest thanks and appreciation for helping me.
 

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Discussion Starter #8
MSG FOR KORDON...sincerest thanks...see text..

Kordon;

Thanks much for your input. Have previously checked both vac hoses which run from intake manifold to vac tank, as well as vac hose running from vac tank into firewall. All three hoses are ok.

Have been suspecting vac tank and/or magnet valve problem, but didn't know how to trouble shoot same. But response from Bob A (below) gives excellent info on magnet valve operation, including elec path. Will use that info to test magnet valve/vac tank operation.

Will keep your info on file also. Can never have too much, hands on, practical info on file.

Thanks again for your response.

Sammy in CT
 

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Discussion Starter #9
Bob ... Just a couple questions.

I do have a couple questions for clarification . I'm trying to figure out the proper connections for the three vacuum hoses that run from the passanger side of the engine compartment to the manifold. One of the three actually appears to be providing vacuum. Is this true? This seems odd to me since it's connecting to the manifold. None of the three were connected when I bought the car about a month ago. I have since connected them to where I think makes sense.

It appears that two of the three were actually connected together via a T connector, which no longer exhists, so I purchased a standard T at the auto parts store. As I look at the T connector in the book, it almost appears to have a vacuum delay valve (or something) built into it, although, it may just be that the artist had fun with the drawing. It seems odd to me that two of the hoses connect together (one providing vacuum and one that is not) via a T, and then connect the two to the manifold unless they're using a nonstandard T.

So, my real question s are...
1. Which two hoses are connected together via the T.
2. Is this a standard T?

I will assume that the other hose connects to the other vacuum location on the manifold.

Can you help?

Many thanks, and sorry this is so long.
kordon
 

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Re: Bob ... Just a couple questions.

I'll try to explain as best I can.

On the back of the intake manifold just in front and to the left side of the EGR valve is a vacuum connection where two of the hoses connect. They are connected to this point with a standard T on my car.

One of the hoses is black with a white stripe. That hose runs to the A/C vacuum tank which is that little tank with the two magnet valves on it just to the left of the engine compartment light.

The other hose doesn't have a stipe on my car and it runs from the T to the vacuum line on the cruise control (ASCD)actuator.

On the A/C vacuum tank are two magnet valves. One has a yellow cap and from that magnet
valve a black with yellow stipe hose runs to the left side of the engine and attaches to the top of the Fast Idle Control Device (FICD) The FICD is a brass colored thingy about the diameter of a half dollar that screws directly into the intake manifold and has the small yellow striped hose connected on the top and a larger vacuum hose connected off the side of it running to the air regulator, and air flow meter boot.

Anyway if your vacuum hoses aren't the same color as mine, you need to connect them in this manner.

Yellow capped magnet valve to top of FICD.
Hose from A/C vacuum (top of tank)to T at rear of manifold and ASCD vacuum to T at rear of manifold.

Good Luck!

Bob A.

> I do have a couple questions for
> clarification . I'm trying to figure out the
> proper connections for the three vacuum
> hoses that run from the passanger side of
> the engine compartment to the manifold. One
> of the three actually appears to be
> providing vacuum. Is this true? This seems
> odd to me since it's connecting to the
> manifold. None of the three were connected
> when I bought the car about a month ago. I
> have since connected them to where I think
> makes sense.

> It appears that two of the three were
> actually connected together via a T
> connector, which no longer exhists, so I
> purchased a standard T at the auto parts
> store. As I look at the T connector in the
> book, it almost appears to have a vacuum
> delay valve (or something) built into it,
> although, it may just be that the artist had
> fun with the drawing. It seems odd to me
> that two of the hoses connect together (one
> providing vacuum and one that is not) via a
> T, and then connect the two to the manifold
> unless they're using a nonstandard T.

> So, my real question s are...
> 1. Which two hoses are connected together
> via the T.
> 2. Is this a standard T?

> I will assume that the other hose connects
> to the other vacuum location on the
> manifold.

> Can you help?

> Many thanks, and sorry this is so long.
> kordon
 

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Discussion Starter #11
Thanks.

I'll take a look at this in the morning and make sure I've got things hooked up right.

Happy New year.

kordon
 
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