HVAC question

[DoubleO7]

On a combo electric heat and a/c unit, what would be the purpose of a "evaporator motor"?

Down here the mobile homes are often equipped with an outside only unit that sits next to the house. It contains both the a/c cooling equipment and the electric resistant heating unit.
there is a 16" flexible insulated duct for the conditioned air and another for the return air.
This morning we switched it over to heat to take the overnight chill out of the house. It started to blow cool air but after a minute of blowing cold air it shut off. Digital thermostat just clicked twice every 30 seconds.
Turned breakers off for a few and tried again.
Thermostat just clicked again twice every 30 seconds.

I took the side panel off the outside unit, looking it over I discovered a disconnected yellow wire. Per the schematic it appears the wire should be connected to the contactor above it.
The schematic shows two yellow wires going from the same contactor terminal to what is called an "evaporator motor".
We had heat last winter but maybe that wire was not on good enough (push-on blade). Or a mouse decided to get in and play jungle jim.

Anyways I can see the power connections for the heating elements are very corroded. And inside the casing was dewy wet.

I am thinking the "evaporator motor" is to blow air thru the cabinet every so often to keep the heating unit at least moisture free and thus prevent corrosion??

Maybe, maybe not.

I reconnected the yellow wire and the results were "no change".

Maybe, maybe not.

 

[guido]

Hello Double07,

Yellow and green are the thermostat wires that usually control the AC
part of the system. That in the photo is the contractor that powers the
compressor side, when calling for cooling. The thermostat selection determined which
system turns on. The furnace fan is turned on on both cycles, unless there are separate systems with their own circulating fan,

Guido.

 

[M-MAN]

You have two motors on that unit. The
condenser motor you can see. The evaporator
motor (usually called the blower motor) is
hidden in the cabinet. It is what pushes
air through the house. Check the capacitor.

 

[M-MAN]

Forgot to add put new batteries in the thermostat.

 

[Steve@Advance]

The terminal the yellow wire is now on is part of the 24v control circuit.

If the yellow wire is going directly to the blower motor, that is not the right terminal. Check your wiring diagram again, there are several terminals on the contactor.

If the unit was blowing air, but no heat, it was not the evap motor that failed to come on.

For some reason the heat circuit is not coming on. It may have tripped a safety over heat, something has come loose on the 24v control to the heat, or the heat may be on a separate circuit breaker from the air.

 

[aquadave]

what you have in the pic has nothing to do with your heat strips that controls the AC compressor can you post a pic of the wire schematic? The evap motor or inside motor is what blows in the trailer. so does the blower not come on at all? Even if you flip the fan from auto to on at the thermostat? when in heat mode the elec strips come on and when they heat up a small quarter size silver thermostat kicks on the blower and the blower will run after it turns off until the strips have cooled. you should have a tall "stacked" black relay that controls your heat strips it very well could be that disconnected yellow wire is not letting that relay get power keeping the heat from coming on. post a pic of the schematic and the black relays I'll tell you what wire goes where

 

[aquadave]

looks like it goes here and yellow is transformer power lets see the diagram 1st before blowing up your transformer

 

[aquadave]

try again

 

[M-MAN]

Definitely need to look at that wiring diagram again. By blowing up the pic there is discoloration on the capacitor post right above the red wire where it looks like a
wire was. My guess is you put the wire on a 24v post and it should be on the run cap for a motor???

 

[Roger Tomfohrde]

My first thought is with the yellow wire and the purple wire together you have the 24 volt circuit and the 240 volt circuit together, probably shorted something out. The yellow likely came from the left hand side of the contactor on the bottom. The loose yellow likely went to the capacitor yellow side. Really need a wiring diagram to sort through this....

 

[DoubleO7]

Sorry Guys, I started a new job today so am away from internet from daylight to dusk.
Here are so pics of the schematic

 

[DoubleO7]

And one more trying to show the corrosion on a 20 month old unit.

The one yellow wire un-connected in my O.P. picture is going further into the cabinet and per the schematic goes to the compressor.
The connected yellow wire goes to the squirrel cage blower below.
As I physically traced it from the contactor to the blower
Which is blowing air over the heating elements.

The a/c is on and the squirrel cage blower is running. But does not the compressor need that yellow wired connected to get cool air?

 

[DoubleO7]

That violet/purple wire left of the yellow wire on bottom of contactor goes off to the right and is wire nutted to the yellow thermostat wire and another yellow wire going deeper into the cabinet just like the yellow wire on the contactor is. So that purple wire should be also considered a yellow wire as it appears to be a siamesed terminal with another currently vacant lug.
But the schematic shows the yellow thermostat wire should be going to a high pressure switch.


Installer is coming Friday or so to look at it.

 

[DoubleO7]

Okay so when I turn on the heat and set thermostat at 85 with fan on "auto" nothing happens.
But the squirrel fan comes on and I get outside temp. air if the fan is switched to on.

Thermostat has no batteries.

Something is not giving power to the heating elements or maybe one or more element is burned out and so none will come on.

 

[aquadave]

The blue on the terminal with the yellow goes up top with the other blues and the disconnected yellow goes with the yellow on the contactor

 

[aquadave]

blue with the yellow goes with other blues and the disconnected yellow goes to where the blue was next to the other yellow thats how your heat strips get low voltage to turn on after they heat up the fan will come on automatically

 

[DoubleO7]

aquadave,
I am not brave enough to be switching wires per your posts.

This unit has been functioning thru one winter and two summers without issue.
No that we want a bit of heat for the second season, it wont.
A/C stills works fine.

Nobody has been inside the unit changing wires or disconnecting any. But that one yellow wire is not disconnected for some reason.
May or may not be the culprit.

Thanks

 

[aquadave]

I understand, that is what the diagram shows but you could still have a potential relay bad that's the tall black one that kicks on the heat strips