4x4 engage but ac only out of defrost......

[thatguy2010]

so yesterday I was reading and the vacuum booster controls the 4x4 and the ac and I was working with the switch controls for the transfer case and it engages just fine....my question is, is there a chance that it's just a vacuum leak or what could be my problem here? the ac is STILL only coming out of the defrost vents. does someone have a vacuum line diagram for a 2000 f350 so I can get my ac working before I leave to Florida in a few days?

[thatguy2010]

anyone? I really need this fixed

[HVACTECH]

what year model truck

[thatguy2010]

2000 f350 4x4.....with manual hubs...don't know if that will matter or not, it worked all the way until last week...

[HVACTECH]

if your truck is set up like my 2001 with manual hubs take a look behind your glove box .... there are 2 tabs on the top that you push in then the glove box opens up past the regular point that it opens to and it allows acsess to the actuator that controls your defrost vents and regular vents .... it is on the passanger side of the truck but on the left side of the area behind your glove box ... pull the vacume line and check for suction when in ac mode.

[thatguy2010]

awesome thanks, and if there's no vacuum?

[HVACTECH]

I am not sure of weather or not the actuator is Normally open or normally closed but I do know that when on max ac the other actuator near by for the ac to pull air from inside the cab is on. if u can connect that hose to the actuator when in max ac (either by adding a small vacuum line from that one or re routing it temporarily you will be able to test and see if it is working properly. I normally work on commercial Hvac and Residential hvac not Automotive but I do know how to troubleshoot it. If the system has no need for a vacuum for air to come out of the vents instead of defrost then I would check the door that directs airflow from defrost to front vents and see if it is stuck.
if the system requires a vacuum to have airflow through the regular vents and no vacuum is present I would check 2 things. first check the other vacuum line that opens the in cab vent to recirculate air on max ac if that vent line has no vacuum then I would assume either a leak or no proper vacuum being generated. If there is a vacuum present then I would start tracing from the tube that goes to the defrost control and inspect for proper operation. hopefully we can troubleshoot this and get it working before you leave town

[bigb56]

Originally Posted by thatguy2010

so yesterday I was reading and the vacuum booster controls the 4x4 and the ac and I was working with the switch controls for the transfer case and it engages just fine....my question is, is there a chance that it's just a vacuum leak or what could be my problem here? the ac is STILL only coming out of the defrost vents. does someone have a vacuum line diagram for a 2000 f350 so I can get my ac working before I leave to Florida in a few days?

No I think the vacuum pump only operates the shift on the fly hubs and the HVAC. The transfer case shifts with electric solenoids/motors. So if you don't have ESOF, your vacuum pump is only controlling your HVAC.
Did you verify that your pump is running? And that it is shutting off? It should cycle on and off. Mine started to run constantly for a couple days then it just died.

Are you sure you don't have ESOF? If you have a dash switch it sounds like you do have ESOF. Look closely at your hubs to see if they say "LOCK" and "AUTO"

[tubular031]

Mine did the same thing till I stuck a golf tee into the vac line going to the vac hubs (which SUCK!) and put warn manual hubs on. Now they lock when I want them to and they stay locked till I want them to unlock. No more guess work!!!

[HVACTECH]

Im sorry I must have misunderstood the problem. Is your point of dissatisfaction the fact that your ac wont go from defrost vents to the regular vents or is it a problem that is effecting your 4x4 that you would like resolved