Vacuum Issues In AC & Heater

[Sompin2do]

On my 90 GT I'm having issues with the blower direction switching by itself when I accellerate. It's going back and forth from vent to defog. How do I check for a vacuum leak? Everything under the dash is connected so maybe it's the cannister? Where is that located? I don't have much troubleshooting experience in this area so any help is appreciated.

Thanks
Mike

 

[jrichker]

You are missing either the check valve in the vacuum system or have a missing vacuum canister or vacuum leak

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

Diagram courtesy of Tmoss & Stang&2birds

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif