# Low & High Speed Fan Settings?



## Sibbles

Hi folks. New to the forum and to the outback products. We purchased a used 2010 outback 210RS this year which has beem great thus far. We love it. One weird observation which we are trying to figure out. The thermostat is a coleman mach 7862 which has a fan setting "low and high auto" and "fan low and high" 4 settings in total. When using either heat or AC the fan only blows in hugh speed regardless of the fan selection switch. It cycles on when called for heat or cool but can not be turned down or just placed in on when on heating or cooling setting.

We replaced the Tstat and still have the same issue.

Do these units actually have two speeds?

Is it possible for both the AC fan and furnace fan to have faulty low speed fans?

Where should we look next?

Thanks all


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## Stumpy75

I have the same thermostat.

The furnace only has one fan speed. That fan is either on or off with the furnace. I'm not talking about a heat coil in the AC (which I do not have and don't know anything about). I'm talking about the propane furnace.

The fan mode sets the AC fan to either come on when the AC runs(Auto), or to turn on the fan manually (ON).

The AC fan speed is controlled my the Low/High switch, no matter if the fan mode is set in Auto or ON.

The middle switch selects COOL/OFF/HEAT. On mine, the fan will run when in the ON mode when the middle switch is either on OFF or COOL.

Is this your thermostat?










Here's how mine was wired. Trailer wires labeled, with OLD thermostat hanging down. Your trailer wiring is probably NOT the same! They used whatever wire they had to run from the AC to the thermostat...










Hope this helps!

Chris


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## Sibbles

Interesting, your tstat is different then mine. Maybe someone has put in a tstat that isn't quite right for this unit.
I have attached what we have currently.

So you are saying your furnace only has a single speed and my AC should have both or I should be able to select either speed in the AC?


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## Sibbles

The coleman mach AP7862


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## Stumpy75

Ok, I originally googled your thermostat and the pics came up as mine, but I went back and looked again, and they are obviously different... Your tstat is what I replaced with the one in the my post above.

My furnace has only one fan speed. That fan speed is not controlled by the thermostat. When the tstat calls for heat, the burner lights and the fan comes on. That's a separate system than the AC, and the only control you have for the heat is turning on the heat and setting the temperature.

From the looks of your thermostat, you should have the same functions as mine, but the controls are configured differently. It took me a little to figure out my old one...

When the system switch is on FAN, only the AC fan will run, not the compressor. You will control the speed of the AC fan by moving the fan switch to the right(the ON side) and either selecting low or high. You should have two speeds. However, even if you set the FAN switch to the left (AUTO low or high), the fan WILL continue to continuously run, just at it did in selecting the ON side. The fan will run until you move the SYSTEM switch to OFF. I always thought that was a little strange...

And here's where it gets a little nuts...*when the system switch is set to COOL..*

With the system set to COOL, and the fan switch still set to the right(to the ON side) on either low or high, the fan will continue to always be on but now the compressor (cooling) will cycle on and off as needed to satisfy the temperature you have on the tstat. Wherever you have the fan switch set (ON low or high), that's what speed the fan should be running at. I have two speeds. as shown on the tstat. And the fan is constantly running.

With the system set to COOL, and you move the fan switch to the left(to the AUTO side) on low or high, the fan will only come on when the compressor comes on. The fan and the compressor will stay on until the tstat is satisfied, and then both the fan and compressor will shut off. Wherever you have the fan switch set(AUTO low or high), that's what speed the fan should be running at. And the fan will cycle on and off with the compressor.

I had the tstat like yours for the first few months, and got tired of the large temperature swings that an analog tstat has, so I replaced it with a digital one. I marked the wires before I removed them from the old tstat, because only some of the colors matched up with the new one.

So, that's how my old one worked. I did have two AC fan speeds available with the old tstat. I was able to have the fan constantly on either with or without the compressor running, or have the fan automatically cycle with the compressor at whatever speed I had set.

Good luck!

Chris


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## thefulminator

I had the same tstat that you did and switched it out for the one Stumpy75 has. There is night and day differences in how accurate we can set the temperature. With the old tstat, we would set it where we thought it should be but would either be roasting or freezing. With the new one it seems to be pretty spot on. Bought mine on amazon for around $70 if I remember correctly. The switch over was pretty easy.


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## Sibbles

This is great information folks. I think we're going to look at changing out the tstat to the one stumpy has shown. I also have to look into why my low speed is not working on the AC. I'm going to guess a wiring problem or a MacGyver fix someone did previous to us owning it. I'll keep ya all posted in how we make out now that i know how it is suppose to work. Thx again


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## bob91yj

I have the same thermostat that you have in my 2017 330RL, and the same issue. Fan speed selection does NOTHING, AC fan blows at the same speed (guessing its high speed) regardless of thermostat switch position.


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## Sibbles

I had a chance to do a bit of troubleshooting the other day and here is what I knkw so far.
When selecting fan and low speed there is no output on the gray wire. However there is 12V on the high speed wire (green). When selecting to high nothing changes. 12V on the green. When you put system to off the green 12V is gone.

At the control box in the ceiling, I took the 12V feed on the green and switched it to the gray input in the box. Fan came in in high speed.

It doesn't appear to have a low speed in the fan unit.

Perhaps I have two problems. One being the tstat output doesn't work and the fan unit input for low speed and messed up only allowing for hugh speed. Not sure how this is controlled. Maybe a resistor failure but I'll have to do some more research.

Frustrating


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