INJECTOR JACK

My 96 3500 heater controls is giving me problems, it will only switch to defrost,defrost and upper vent modes only I don't get floor or floor and vent anybody else had this problem?

Partsman

Look right above the gas pedel and you will see the vacuum motor for the duct door. Pull the vacuum hose off and see if you have vacuum at the hose. IF you have vacuum you need a new motor, if you don't have vacuum check all your vacuum hoses under the hood. Do you have cruise control and does it work?

INJECTOR JACK

I have cruise and it does not work any tips as to were i should be looking I figure they may be related. I do have vacum boost brakes and that part is working ok.

Partsman

Yea, check the hose going to the cruise servo under the drivers battery they are rotorius about rotting off for battery acid. I have also seen the body of the servo rot.

jon96ctd

i've got a similar problem on my 96...A/C and heater both work but it only comes out either the defroster or the floor vents, no dash vents. cruise works fine. i'll be diggin into that soon, let me know what you find out if you get to it before me...

INJECTOR JACK

Checked out the heater controls it was the servo by the gas pedal I just pulled the line of to see if i had vacum and i did, servo must have a hole in the diagram.Cruise control has a electrical problem it only lights up when she feels likeit. Thanks for the info guy's