1992 Dodge extended van with 318 v-8 engine
With aircondition selector switch on max vent, while driving on interstate, 65-75 mph...(when the van is cruising on a plain level highway...the aircondition continues to blow out through the vent as selected....however during an incline, the automatic transmission don't shift to maintain cruising speed. the max aircondition will transfer the vent air involuntarily to defrost.. any suggestion on what is causing this.
you have a vacuum leak or ck valve is bad.Find the small hose that goes through the fire wall, and follow it back to vac. resivoir. There may a ck. valve built into the resivoir or follow hose toward eng. there may be one INLINE. you can test it by sucking on it.should hold vac. in one direction, but not the other. Hope this helps.....
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