Recirculation for E450

Erik63 wrote:

j-d wrote:
I think your interest in this would be better served with adding a switch to the compressor clutch, vs. a valve to vacuum controls.

Does this mean that you would use the max A/C switch but then disable the compressor?

Yes, but there's really no need to do this if you can settle on a temperature with the compressor still running.

More I think about it, there's a problem: If you disable the compressor, the "vent" temperature is going to climb, because the Heater Core is still HOT. Then you'd have to put a water cutoff valve in the heater line, and that could affect circulation in the engine cooling system.

Best to leave it as-built and set temperature with the Knob.

j-d wrote:
I think your interest in this would be better served with adding a switch to the compressor clutch, vs. a valve to vacuum controls.

Does this mean that you would use the max A/C switch but then disable the compressor?

Thanks for everyone's help, this has given me a better idea of how this works.

Erik63 wrote:
So if it is cold outside do you just crank up the heat, or is there a way of intercepting the vacuum line that goes to the valve that controls whether the air is from inside or outside?

Thanks.

Yes, simply adjust the temperature to "heat".

Keep-in-mind that when set to max a/c with the heat on, it is perfect for defogging and defrosting your windshield because the a/c unit removes the humidity in the air it is blowing. So when you can't see through your windshield because there is frost or water on the inside, max a/c is the setting you want anyway. Even when there is frost on the outside, max a/c will blow hotter because it is working with air previously warmed-up from inside, instead of ice cold damp humid air from the outside. In the winter, max a/c will take the chill out of your motor home much better than normal a/c. That is unless your rig leaks air badly. Then you will want outside air to maintain a positive cabin pressure to leak warm air outward instead of cold air inward.

The a/c compressor will shut off when the temperature goes below a certain outside temperature. I don't recall what it is, but it is 20 something degrees F.

I learned over the years that recirculating air without the a/c on is a setting to avoid in summer and winter. With our E350, I wish I could recirculate the air from the vents in the dash board to blow recirculated air further into the cabin....most importantly when driving through Salt Lake City where the air pollution is tremendous.

We live in FL where it's usually so hot and humid that the Temp Knob is always set to Coldest, with Select in Normal A/C or Max A/C. In Max, many vehicles also set the Blend Door (Temp) to Coldest (over riding the Temp Knob setting) but I believe the E-Series lets you change Temp in Max.

You're referring to what I call "Japanese Controls" where there's a Select Knob, a Temp Knob, a Recirc Button, and an A/C Button. A/C Button allows you to turn the Compressor OFF even in an otherwise A/C setting. Not every setting, by the way. I think you still get Compressor in Defrost.

Anyhow, try seeing if you can raise Temp on the Blue-to-Red Knob with Mode Select Knob in Max. I think you can, at least on some model years. But if you can't, I think your interest in this would be better served with adding a switch to the compressor clutch, vs. a valve to vacuum controls.

You probably could create a mod to make it just swich to recirculate but it's easy enough to select Max A/C and dial up the temp.

Erik63 wrote:
So if it is cold outside do you just crank up the heat, or is there a way of intercepting the vacuum line that goes to the valve that controls whether the air is from inside or outside?

Thanks.

I would think MAX AC with the heat set at hot.

A GREAT way to eliminate moisture inside a vehicle is to run the AC in the winter with the heat. First learned this trick when my Hyundai Elantra would turn on the AC when you selected defrost. REALLY pulls out the moisture!

So if it is cold outside do you just crank up the heat, or is there a way of intercepting the vacuum line that goes to the valve that controls whether the air is from inside or outside?

Thanks.

theoldwizard1 wrote:
MAX A/C recirculates the inside air.

Correct!