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You definitely have a vacuum leak. The default setting for all of the climate controls without any vacuum results in hot air being blown out of the defrost vents. You also probably can't get the air to change vents regardless of which button you push. The solution is to buy a vacuum pump from Autozone or Pep Boys for about $30. Connect it to the vacuum line that comes from the vacuum tank that goes through the firewall to the climate controlls under the dash. Pump up the vacuum. If you can't get it to hold vacuum, then you have a starting place to start looking for the leak. You should be able to hold vacuum on this line, no matter what. If this line holds vacuum, then try the one going from the vacuum cannister to the heater control valve. This one should also hold vacuum, no matter what. If it does, then plug everything back up and apply vacuum to the hose that runs from the intake plenum to the vacuum cannister. This will take quite a few pumps to get it up to 12 or so. It should hold vacuum. If it does, then your leak is coming from one of the other lines coming off of the plenum. I chased my leak down to the floor vent swith that is located right above the drivers right knee. Someone had hooked it up backwards allowing the check valve to release the vacuum. I hope yours is as easy to find. One other hint, make sure the hoses fit tight. If they seem the least bit loose, cut off about a quarter of an inch, so the new material will make a good seal. Good luck.

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โˆ™ 2004-11-29 18:06:06
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Q: Why would a 1987 Nissan 300ZX climate control only blow hot air on all settings?
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