On a 2000, the control has a position for vent and floor together. However it is bracketed in the "AC" section. This postition does the best job of heating the truck but I'm concerned it's running the AC compressor and toasting the mileage.

Is this true?

Thanks

 

Only one way to find out. Put it on that setting and pop the hood. Watch the A/C compressor. Most people don't realize that when you select windshield defrost, that ALSO turns the A/C on.

 

Yes, the compressor would be running on that setting.

 

darn.

 

Why do you think that it would "toast" your mileage? I do not believe that your compressor will be trying to make it max cool while in this mode so the compressor will not just be running for all it is worth... You do have the temperature **** in the heat position which would cause the compressor to maybe run periodically actually removing moisture from the interior, but I do not think it would impact your mileage all that much.

If you were really concerned about it, drive it for a week with the A/C compressor clutch unplugged. I would only do this as a test.

 

Having the ac on always wrecks the mileage. Maybe not so much on this as it gets such poor mileage to begin with but I don't want to make the problem worse.

I still wonder if the heater is working properly. I've had the thermo changed and the heater core and system flushed.

The blower motor is making asmall noise but I can't imagine it's effecting the heat output.