W20 AC acting wierdly

lvanduyn · 05-18-2010, 02:52 PM

I have a W20 chassis with something strange going on with the AC controls. Basically, the compressor runs in all control positions except OFF and the vent position directly to the left of the OFF position. It runs in all positions to the right of the OFF position. With this going on, the compressor is running even when I want heat.
Does any of this ring a bell with anyone out there?
Thanks, Larry

Fred and Bonnie · 05-18-2010, 08:38 PM

You didn't state your coach manufacturer, however I feel confident that all the different manufacturers set-up the climate controls identical to your coach. I believe the rational is it's moisture control.

fred

brucemcdou · 05-19-2010, 08:24 PM

Larry - we have a 2008 W22 Chassis, and our climate control is set up the same way. The AC compressor is running (and using fuel and sapping engine power) in all positions except for "vent," first selection to the left of "off." I understand Fred's point that the manufacturer assumes if you're using the heater or defogging outlets you must need dehumidifying, but that's not true. We frequently use the defogging outlets on cold (outside only) air because the dash vents are positioned poorly and they blow right on us. It's frustrating as those of us who live in places where the temperature is mild year-round are generally smart enough to select "AC" if we need dehumidifying on our cars, so why can't we in our motorhome?

**"007"** · 05-20-2010, 05:19 AM

Your AC compressor should have a clutch that will only engage when your control calls for AC. The fly wheel will always spin because of fan belt. Maybe your clutch needs to be freed up and you might get better mileage.

lvanduyn · 05-20-2010, 07:02 AM

Quote:

Originally Posted by brucemcdou

Larry - we have a 2008 W22 Chassis, and our climate control is set up the same way. The AC compressor is running (and using fuel and sapping engine power) in all positions except for "vent," first selection to the left of "off." I understand Fred's point that the manufacturer assumes if you're using the heater or defogging outlets you must need dehumidifying, but that's not true. We frequently use the defogging outlets on cold (outside only) air because the dash vents are positioned poorly and they blow right on us. It's frustrating as those of us who live in places where the temperature is mild year-round are generally smart enough to select "AC" if we need dehumidifying on our cars, so why can't we in our motorhome?

Hi Bruce
So I am not the only one with this configuration. GM has been using this same basic control forever. I have had it in a number of vehicles and it does not operate this way. The owners manual for the coach states that the compressor should run only in the defrost and AC positions. We live in the southwest and don't have a lot of need for defrost but do need heat occasionally. I really don't like having the compressor running when I need a little heat. Maybe it is time to wire in a disable switch..
Larry

scoutmstr · 05-23-2010, 02:57 PM

I agree and have wired in switch to let me control when the AC compressor is engaged. The switch is an AC switch that lights up when engaged. If you're interested in doing this respond and I'll post part numbers and wiring mods with pictures.

lvanduyn · 05-24-2010, 07:25 AM

Hi Scoutmstr
Yes, I am very much interested in what you have done and would appreciate seeing the details.
Thanks, Larry

2008 Safari Trek

TrekPR · 05-24-2010, 12:07 PM

Mine does the same and I would also be interested in your cure.

scoutmstr · 05-24-2010, 02:06 PM

To install a switch so that the AC will work or not work in any position you want. You have total control of when the AC clutch is activated. First thing is to buy a switch made by Toyota which is made for AC control. The part number is 84660-22021 and was $17.18 when I bought it in March 2007. It is a push on push off switch that is lit when on.

Attached are two pictures. If your unit is an Evans Temco and looks like my dash, the second picture is the wiring diagram and modifications for that unit. On the backside of the rotary switch that controls where the air flows (it has pictures/words of vent, AC, Max AC, etc) there is a single blue wire with a number of red wires. The blue wire controls the thermostat and eventually the clutch. That wire is cut. The part of the wire from the unit is capped and not used. The part of the wire that comes up from the wire harness has an extension (use same gauge wire) and is run to a 15 amp relay. The opposite terminal on the relay has a wire run up to the unit (vacuum mode switch) and is “teed” into that (RED)wire.

You now have the control of the blue wire (AC) to the opposite side of an ignition hot (RED) wire. On the other two terminals you wire to the added Toyota switch. From the ground side of the relay you must also run a wire to ground. The Toyota switch has three wires two blue and one white. Use an ammeter to determine which is hot, ground and light.

Drill a hole throught the dash to mount the switch, See my picture. Since most of us don't have metric drill bits and the diameter of the switch is metric there will be a gap around the switch. If you look closely, you'll see a small O-ring around the switch. It just slides over the switch and hides the hole and looks good.