weird heater blower issue

[markanthony]

I have a 99 xlt with 5.9L. When I have the heat blower on say high blowing at my feet only. I driving around and say give some gas to pass or get on the freeway, or in a hurry ( gas pedal floored or in good enough to watch the gas gauge drop) The air will be redirected to defrost the windshield. I also have noticed that in the last month that when I am parked with the engine running. The idle will rev up a few hundred RPM'S then back down, when I have the heater blower switched to vents & feet. Like the A/C compressor is Engaged. Any thoughts..
I replaced the ALT middle of last year. The windshield probably should be replaced. It is pitted. I have read about the GEM deal and seems like it affects most of the dash problems all at once...


Another quick thought. The GEM. Does it control the little digital read out for millage??? Mine will go out every once in a while. I tap on the plastic gauge cover and it comes back on.

Thanks.

 

[Sparkomatic]

I have an '02 Eb with 5.4 and is doin some of the same things. When put foot into it will default to defrost until the vacuum comes back , It will not blow on the floor.. I have checked the check valve and resivoir and all checks out, As well the odometer goes out once in awhile . Not so concerned about that , but the heater issue is needing attention, as it is cold out , and there is also a very cold draft on pass side coming from recirc door.

 

[Thermo]

If your dampers are changing positions when you step on the gas, you need to check the vacuum lines that are controlling your dampers in the dash. These are known to develop leaks and what is happening is at normal throttle, the system can keep up with the leakage. But, you open up the throttle and the vacuum in the intake drops, resulting in not enough vacuum to keep the dampers positioned to the floor. The leakage can be either in the engine bay or in the dash.