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Discussion Starter #1
Hi guys,

Whenever you ask someone about the heater/AC vents blowing defrost rather than other vents, the first response is “you must have a vacuum problem”. If you haven’t investigated this problem, you will need some small “educated” creature to slither around the many, spaghetti-like hoses emanating from a solenoid manifold attached to a wall under the dash.

I took the dash along with the main plastic vents out of the car hoping that I could gain better vantage for inspection and or replacement. WRONG!!!! From what I could see, the hoses appear to be fine but I am replacing the one that runs the width of the dash that showed signs of crimping at various hold down points.

My questions are: Has anyone had to replace any of these hoses around the “manifold”? If so, how did you get to them? How does one go about diagnosing vacuum problems if he can’t disconnect or isolate a particular hose? And lastly, has anyone had problems with any of the many small solenoids that control the HVAC system?

I eagerly await your responses.
 

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i need to take my dash out and troubleshoot some stuff too. My main vents wont blow any air but all the other ones will. I think the door that opens the ducts to those vents is broken because all of the vacuum valves still open and close properly.
Its been a problem since July i've just been too lazy to figure it out.
 

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Discussion Starter #3
Thanks phxz31. The dash is rough especially those 4 bolts just below the windshield. I think that now my problem is even deeper. Since I have been working with it, the only thing that works is the manual defrost. My electronic controls won't even light up.
 

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I think a gerbil would be better. Squirrels can be demanding when contract negotiations come up. They get fat an lazy this time of the year.
 

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Gary,

There are 3 vacuum hoses in the engine compartment that are usually the starting point ot fix the vacuum problems. The vacuum canister behind the passenger headlight is where these 3 hoses 'originate'. ! goes through the firewall to HVAC system, 1 goes to the water ****, 1 goes to the manifold. The tips of these hoses, assuming they are OEM original, are actually color coded assuming the colors have not faded due to age of the vehicle. 9 times out of 10 it will be blantantly apparent when you inspect them if they are bad. They will be very brittle, and most of the time cracked at the nipples where they connect. This fix tends to correct MOST of the auto AC problems, however there are still endless possibilites even if the engine compartment vacuum lines are ok. One other common faliure I have seen ( I have actually owned 8 Z31 cars over the last 21 years), is a diaphragm on the blower motor that operates the "Recirculate" function to the unit. This diaphgram, kind of like the texture/material of a speaker woofer, can crack with age. And if that too checks out ok, then you are opening the pandora's box to the auto AC. I had one 87 Z that I just completely gave up on. I changed out all of the solenoids above the gas pedal, all of the lines in the engine compartment were ok, the blower motor was fine, and I was left clueless!
If you need any help identifying the engine compartment lines, let me know and I'll snap some pictures.
 

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Discussion Starter #6
imsaqtp,

Thanks a bunch. I knew that someone out there had some experience with this. I did not know about the diaphragm on the blower motor and have not checked it out.

If you have pics of where the diaphragm is, I would appreciate seeing them.
 

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try tracking down a tool dealer or someplace that has a vacuum leak detector.
 
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