1998 lumina A/C problem

hello all , i recently purchased a 1998 chevy lumina
3.1 V6 , 75k , and under hard acceleration or hilly driving the a/c will drop to the floor , and no air at all will come out of the a/c vents,
does anyone know what causes this and how to fix it?

also the a/c is very cold at speed but stop and go it will warm up 20 to 30 degrees or so, from 40 to 70 degrees, why does it doo this , my 90 chevy p/u
does not do this , i am confussed,/

thanks , lee

hello all , i recently purchased a 1998 chevy lumina
3.1 V6 , 75k , and under hard acceleration or hilly driving the a/c will drop to the floor , and no air at all will come out of the a/c vents,
does anyone know what causes this and how to fix it?

also the a/c is very cold at speed but stop and go it will warm up 20 to 30 degrees or so, from 40 to 70 degrees, why does it doo this , my 90 chevy p/u
does not do this , i am confussed,/

thanks , lee

The air is switching vent position because of a vacuum leak, probably under the hood on the front driver's side near the vac resevoir...when you step on the gas, vacuum level drops sharply, so if there's a leak in a system that operates on vacuum supply, that's when it'll drop out.

As to the other question, it's either low on charge or the aux fan isn't working on the radiator, and the condensor doesn't have enough airflow when it's not moving....

thanks for the reply,
i checked the aux fan and it's working, as for the low charge, i will have to take it to the a/c shop to check that out,

i checked the the vacumme out with a gauge and it holds 19-20 at idel and while revving the engine it will increase too 22 .
the vac resivor will hold vacumme for a long time after the car is off ,think its o.k.,
the problem must be in the line that goes into the car:banghead:
or under the dash

In the left front fender, up front, there is a vacuum storage ball (cannister). It's only purpose is to hold the HVAC doors in position when engine vacuum drops (during accelleration).

In order for it to work, it has to be isolated from the engine by a check valve. This check valve is in the vacuum line to the cannister, generally around the battery.

Take it out of the line and check it - you should only be able to blow through it one way.........Bet it's bad.

In the left front fender, up front, there is a vacuum storage ball (cannister). It's only purpose is to hold the HVAC doors in position when engine vacuum drops (during accelleration).

In order for it to work, it has to be isolated from the engine by a check valve. This check valve is in the vacuum line to the cannister, generally around the battery.

Take it out of the line and check it - you should only be able to blow through it one way.........Bet it's bad.

i was thinking about that too, thats where i checked the vaccumme at
drove it today and every tiny hill i dropped out , sometimes on the onramp to the freeway and it getting worse day by day
i will check into that tommorrow ,
too hot here in so cal right now 103 degrees.

thanks