Blower motor

[rahh]

My mother has A Colemann-Evcon # AH16W20BA airhandler. During a storm a few days ago her circuit board was fried. Her technican by-passed the board so she could have AC until the board came in. He installed a new board $675.00 but the blower continued to run. Then he installed a new thermostat Honeywell TH5220D $225.00 & this did not cure the problem. He then replaced the thermal limit switches & charged her another $185.00 & the blower still runs all the time.
She is now out over $1100.00 & he tells her that since it Friday he could not come back until Monday unless she wanted to pay the appropriate over time rate.
When she informed me about this I phoned him & I am waitng for a return phone call.
I have gone over the work he has in place & the wiring is correct according to the schematics. I also have done some research on the web to see where the problem may be.
From what I have read the only thing that has not been replaced would be a fan relay. I am a Construction Superintendent & a Carpenter by trade. "Please do not hold that against me"    I have a good working knowledge of schematics however, I cannot find a fan relay located on the schematic unless it is the small plastic connecter that the black, brown, & orange wires plug into on the blower motor.
All advice is most appreciated.

Rahh

[TECH X]

Well you say the tech bypassed the board to provide A/C.  I assume all he did was wire the high speed fan to continuous power.  Did he remember to put the black fan lead back on the board?  Maybe it's a simple as that.  Trace the black wire from the fan...where does it go?  It should go to the board.  The fan relays, I believe, are built onto the board.

Do not deal with this tech, he is incompetent.  Call his service manager on Monday, and demand he come out.  Ask to have the thermostat and limit switch put back, as they obviously aren't required.  There is a wiring problem here.

Do you have a multimeter?  Turn the thermostat fan to AUTO, and the system to OFF.  Go to the furnace, and measure between G and C on the board.  Do you have 24V?

What colour wires leave the motor?  They should all go to the board or capacitor.

[rahh]

Tech X,
I do not know how he bypassed the board, I do know the black high speed wire goes to fan on the the board as shown in the wiring diagram.
There is a brown coming from the blower to the marked br capacitor , a orange from the blower marked or to the capacitor, & a black coming from the fan marked high going to fan on the board.
There is no voltage from G - C
There is 26 volts from the transformer @ the black & red.

There is 235 volts @ the brown on the capacitor & 115 volts @ the orange on the capacitor. These readings are by checking from ground to brown & ground to orange

The thermostat is L=purple, white on aux & a jumper to E, G=green, O/B= orange, C=black,Y=yellow, R=red with a jumper to RC

[TECH X]

So what colors go to the capacitor?  One brown, one red and one orange??

Is there 120V at the board where the black lead connects to the HIGH terminal?, measure to ground.

There are no other fan speeds going to the board?

I don't think you want a red wire on the capacitor, that could be the low speed fan getting power from the capacitor and running continuously.

[rahh]

Tech X,
I made a typo in my last post. "Sorry" I am not used to staying out late.
There is brown, orange, black.
There is 115volts on the board where the black connects.

[TECH X]

Hmmm seems like the board is energizing your high speed.  Did you remove the black wire from the board when you tested for 120V?

There must be a white neutral wire from the board, are there not any other colors (speeds)?

If the thermostat fan is set to AUTO, there should be no 24V at G.  If the thermostat system is set to OFF, there should be no 24V at Y.  The fan relay on the board should not be energized.

Is there possibly a fan switch installed on the furnace, that might be causing the fan to run continuously?...I doubt it because you would see it wired in series with the fan wiring.

Usually when a board fails, the fan relay stops energizing the fan.  It would be uncommon to see one that is always energizing the fan.

I am curious now...

[rahh]

Tech X,
I turned the power off  & unplugged the new thermostat, turned the power back on checked to see if there was power @ the red & black on the thermostat & there was 26 volts. To my surprise with the face of the new T-stat off the blower motor was off. De-energized plugged the face in & re-energized t-stat off & on auto the blower fired right back up.
So I de-energized, took the t-stat connctions loose @ the air handler, hooked the old T-stat up bypassing the wires going upstairs & it works just like it should.
I hooked the old t-stat back upstairs & still had the same problem. So I have one spare wire that was never used & hope that only one wire is shorted out in the run.
It would be pretty hard to run all new t-stat wire from the air handler to the t-stat location.
Thak You very much for all of your help & patience.
Rahh

[TECH X]

You could look at using only 2 of the good thermostat wires and a remote thermostat kit.  You install a remote in the wall at the thermostat and a reciever down at the furnace.  That would solve the need for 4 or 5 wires.

Fast Stat

I don't think the problem is a short in the low voltage wiring.  The only way the thermostat could get the fan to run is from a call for heat or cool, or energizing G.  The fact that you had 0 Volts at G when the fan was running rules out the possibility of G shorting out against R.

[rahh]

Hello Gentleman,
I did run a new thermostat wire to the air handler & resolve d the coolong issue.
Now that it is time for heat another problem developed.
When the thermostat is placed in heat mode the air handler & the heat pump both turn on & run. However the circuit beaker @ the main panel box trips to the center position. Both units continue to run but they blow cool air & continue to run all the time when the T-Stat is on auto.
The only time the units turn off is when the T-Stat is in the off position.
Thank you for your help.
Rahh