cooling fan problem

I was hoping maybe someone has seen this problem. My cooling fan runs on low speed all of the time when I have my airflow set to vent/floor. If I have it set to just floor or just vent the fans don't run all the time, but as soon as i switch it back to vent/floor, the fans kick right back on. Also, it doesn't seem like my engine temperature is getting as hot as it should, and the air out of my vents does not seem to be as hot as it should be, even when I have it on a setting where the fans are not running all of the time. I have already tried changing the thermostat for the not heating up enough problem and that did not make any difference. Any suggestions would be greatly appreciated. thanks.
1996 3.0

That's by design. The only settings that will not attempt to engage the A/C compressor clutch are the Floor, Vent, and Off positions. The Floor/Vent, Max, Norm, Mix, and Def settings all request A/C via the PCM and Constant Control Relay Module (CCRM).

The lack of heat from the panel vents could be due to a restricted heater core, vanes on the water pump that are deteriorating (would likely also cause overheating conditions), an air pocket in the cooling system, or be psychological due to the radiator cooling fan running. I'd start by making sure the air is purged from the system, especially since you recently replaced the thermostat. After several miles of driving, what is the temp gauge getting up to?

-Rod

It doesn't matter how long i drive, the temperature guage never gets up to the 1/4 point on the dashboard guage and this did not change at all after replacing the thermostat. After replacing the thermostat, I ran the engine for a considerable amount of time with the cap off to try to purge any air out of the system. Am I right in assuming that there is not an actual radiator cap that is accessible on this system? I did have a thought that maybe the heater core could be plugged, but would that also cause the actual coolant temp not to heat up also, or just not much heat from the vents. Thanks for the reply.

I didn't know that about the floor/vent setting, what is the reasoning for the floor/vent position requesting a/c? I would think that if the floor didn't and the vent didn't, then the floor/vent wouldn't either. thanks for reply.

The pressure cap for the cooling system is the cap that is on the overflow tank. You're right, there's no cap on the radiator, but the purpose is served by a properly working cap on the overflow tank.

Also, you're right that a plugged or restricted heater core would not cause the cooling system to run cold, but it could explain the reason there's little heat blowing from the vents. If you have an IR thermometer see if the cooling system is staying as cold as the gauge would imply.

I cannot answer why the engineers wired the HVAC controls to engage the A/C when the vent/floor position is selected.

-Rod