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Discussion Starter #1
83ZXT with auto temp control.

NO HEAT AT ALL. Only defroster works...and then only gives COLD air...even with temp control lever in full hot position.

HEAT VALVE appears stuck CLOSED, as follows: Hose under hood which brings hot water INTO cabin is HOT. Hose under hood which brings hot water OUT of cabin is COLD, and has NO WATER in it (with car at oper temp and temp ctl lever full hot position).

Found a leak at heat valve has corroded the vacuum module (which is connected to the heat valve). Could a defective vacuum module here be preventing the air mix door from operating?

Could non-functioning air mix door be causing no heat condition in cabin?

Thanks to all who respond.
 

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Discussion Starter #2
Re: 83ZXT: quests on auto temp ctl/heat valve/vacu

> 83ZXT with auto temp control.

> NO HEAT AT ALL. Only defroster works...and
> then only gives COLD air...even with temp
> control lever in full hot position.

> HEAT VALVE appears stuck CLOSED, as follows:
> Hose under hood which brings hot water INTO
> cabin is HOT. Hose under hood which brings
> hot water OUT of cabin is COLD, and has NO
> WATER in it (with car at oper temp and temp
> ctl lever full hot position).

> Found a leak at heat valve has corroded the
> vacuum module (which is connected to the
> heat valve). Could a defective vacuum module
> here be preventing the air mix door from
> operating?

> Could non-functioning air mix door be
> causing no heat condition in cabin?

> Thanks to all who respond.
We have converted these to manual controls no prob
lem. The manual setup bolts in without discharging
the a/c. We have also fixed the climate control
system, only to have another vacuum pod rust up
and stick, causing no heat, defrost only, cold air only, etc.
It takes about 100.00 to get the replacement parts for manual heat from us. thanks, joe
 

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Re: 83ZXT: quests on auto temp ctl/heat valve/vacu

> We have converted these to manual controls
> no prob
> lem. The manual setup bolts in without
> discharging
> the a/c. We have also fixed the climate
> control
> system, only to have another vacuum pod rust
> up
> and stick, causing no heat, defrost only,
> cold air only, etc.
> It takes about 100.00 to get the replacement
> parts for manual heat from us. thanks, joe

Why would you want to ditch the auto climate control system? This is actually a pretty nice feature. I'd say, just fix the system you have. You'll need the factory shop manual ( look in the Archive under Dyment. ) You won't be able to do it without that, aarrgh!!! Actually, the climate control section is not the strongest part of the factory shop manual, but I can confirm that the information is all there. Don't ask me to summarize it, it's really a pain in the ass ( but you should work thru it for the sake of your soul and your brow. )

Doug Dawson
[email protected]
 

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Discussion Starter #4
Re: 83ZXT: quests on auto temp ctl/heat valve/vacu

Same problem in my car a while back, the way I solved it was (shop diagnosed and replaced these):

- Replaced the heater ****/valve (also oozing)

Don't have part #, around $70
- Replaced Amp Control for Automatic A/C

Part # DAT 27721-P9700 $28.34
- Replaced Vacuum Valve (bad temp vac. selector)

Part # DAT 27098-U8800 $33.69

It cost me major bucks in labor since they had to remove the dash (right side mostly) to diagnose then replace the parts. If you can do this yourself you'll save some money. Good luck.
 

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Discussion Starter #5
Thanks much..just three more quests...

> - Replaced the heater ****/valve (also
> oozing)

QUEST 1: did this heater ****/valve have a vacuum module (about 1.5 diameter) attached to it?

> Don't have part #, around $70
> - Replaced Amp Control for Automatic A/C

COMMENT: This unit receives resistance signals from various air temp sensors, determines the average resistance of all those signals, then sends a signal to the transducer, wherein the transducer initiates vacuum to various door actuators as called for by mode setting (i.e. auto, low, high) and temp setting

> Part # DAT 27721-P9700 $28.34
> - Replaced Vacuum Valve (bad temp vac.
> selector)

QUEST 2: The vacuum valve and vac temp selector are two different things, that work in conjunction. The vac temp selector controls routes vacuum to the vacuum valve. The vac temp selector is located behind the a/c control panel. The vacuum valve is located behind the glovebox. Which of these two units did you have replaced?

> Part # DAT 27098-U8800 $33.69

QUEST 3: What was this part name?

> It cost me major bucks in labor since they
> had to remove the dash (right side mostly)
> to diagnose then replace the parts. If you
> can do this yourself you'll save some money.
> Good luck.

COMMENT: Have most of dash out already. Can see every part you've identified. Not much room to work in under dash, but think I can replace the parts. Not that I really WANT to do THAT much work, but will if I have to.
 

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Discussion Starter #6
Re: Thanks much..just three more quests...

Sound like you're up to your elbows in dash trying to fix your Auto-Climate controls...good luck to you. I gave up on mine. Everything works fine except one thing. I can only get cold air by moving my temp control lever to the far left. If I move it into any other temp range I get MAX heat....any suggestions?

Mark Z.

> QUEST 1: did this heater ****/valve have a
> vacuum module (about 1.5 diameter)
> attached to it?

> COMMENT: This unit receives resistance
> signals from various air temp sensors,
> determines the average resistance of all
> those signals, then sends a signal to the
> transducer, wherein the transducer initiates
> vacuum to various door actuators as called
> for by mode setting (i.e. auto, low, high)
> and temp setting

> QUEST 2: The vacuum valve and
> vac temp selector are two
> different things, that work in conjunction.
> The vac temp selector controls
> routes vacuum to the vacuum
> valve. The vac temp
> selector is located behind the a/c
> control panel. The vacuum valve
> is located behind the glovebox. Which of
> these two units did you have replaced?

> QUEST 3: What was this part name?

> COMMENT: Have most of dash out already. Can
> see every part you've identified. Not much
> room to work in under dash, but think I can
> replace the parts. Not that I really WANT to
> do THAT much work, but will if I have to.
 

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Discussion Starter #7
Re: (answers here)

> QUEST 1: did this heater ****/valve have a
> vacuum module (about 1.5 diameter)
> attached to it?

I don't remember seeing anything like that when the mechanic showed it to me (just under passenger side dash).

> QUEST 2: The vacuum valve and
> vac temp selector are two
> different things Which of
> these two units did you have replaced?

It was the vacuum valve.

> QUEST 3: What was this part name?
You mean the vacuum valve, or amplifier control?
 

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Discussion Starter #9
Re: 83ZXT: quests on auto temp ctl/heat valve/vacu

I have a '81 ZX with auto climate control. The system works wonderfully when sitting still. If I set the A/C on auto and drive (any type of acceleration), the system switches the vents from A/C to defrost and starts blowing heat. The dealer replace all the vacuum hoses but the problem still persists. Any ideas?
 
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