deluxe blend air II unit

[Guest]

EB23 electric York furnace - the problem starts when we switch from heat to cool or cool to heat. The 3 amp control fuse blows and the lower control board is wiped out (part # 51-7681-317P. We've had 3 boards installed so far with no permanent solution. To get the air cond. or furnace to work, I have to disconnect the wires from the lower board. This stops the fuse from blowing and enables the heat and air to work, but the Deluxe Blend Air II unit runs continously after doing this. The technician has run out of ideas on how to resolve this problem.
This is a new Nashua Manufactured Home. We moved in during December 2006. Any ideas? HELP!!!!

Bruce

[hvac1000]

Since your home is so new I would feel that you should still be under warranty.

I also believe that something is wired incorrectly or there is a short in the low voltage wire system. The only way to tell about a short is to go looking for it but before you do I would put a in-line fuse in the line that seems to blow the boards. It is easier to replace the fuse during testing that keep replacing the board and cheaper to for the company doing the warranty work.

Make sure the service person has the correct set of drawings for all electrical systems associated with your HVAC system before they begin work. It is easier to know where each wire belongs and check they are where there are supposed to be. A good meter will also allow you to check for proper voltage and grounded conductors on the low voltage wiring.

[Robert]

Remove the screws to Blend Air control box and turn the control box around to see lower control board.

On the upper right side once box is turned around, just above the two purple wires is a 4 wire plug.

It plugs into side of control box and runs up to attic fan on roof and connects at upper control board.

Check that harness carefully to ensure that none of the 4 wires are touching each other anywhere inside that harness.

Also check the plugs to be sure no bare spots where wires can touch.

Look closely at all other wires entering the control box to be sure no bare spots are allowing wires to touch metal or each other. Look for pinched wires at entrance and exit points.

The problem will be in the low voltage circuit of the blend air system.

Disconnect the Red and Yellow or Black wires on left side of lower board and turn on system. Have your meter leads pushed up in those two wire connectors, one in the red and one in the yellow or black (whichever color yours is).

Test for 24-28vac.

IF you have 24-28vac there, check that harness between the two boards very closely including the two plugs, one at each end.

Also, whenever you remove the wires and thus remove the 24 vac to the lower board, the attic fan will run continously as it is supposed to.

Hope this helps, if you still don't locate the fault, post back.

Take care and best wishes,
Robert

[Guest]

Vexar by York Furnace Model #EB23B

Hello Robert,

The Coleman representative is still stumped on the problem with the deluxe blend air II unit. Everything seems to check out until the black common wire from the transformer is connected to the lower control board, thats when the fuse blows. We installed each wire individually on the primary side of the board and the fuse stays intact until the black wire is installed. I personally think that the board is shorted out. The representative brought the wrong board.
He brought the one for a gas furnace instead of an electric furnace.

I have a question - on step 4, Check the Motorized Damper, it states the damper does not open, verify that it is receiving 120 volts. Don't you mean 24 volts, because that is the voltage of the damper motor on my furnace. Thanks again.

Bruce

[Robert]

Hi,

Yep, that's a mistype in the troubleshooting steps, should have said 24vac.


Changing out 3 boards pretty much rules out the board itself as being the problem.

Since it only happens when the Black wire is connected, he needs to trace test back from there to locate the short.

Has he tested that Black wire to ground to see if it's powered ?


The Blend Air system is seperate from Furnace. There is only two lower boards for blend air systems. One for all blend air excepr " B " systems and then one for " B " systems.

Two lower and one upper.

Might need another Tech cause this shouldn't be that difficult to locate an obvious shorted circuit.

Here's the lower blend air board 7681-317P:

http://www.mobilehomerepair.com/media/i ... 1-317P.jpg

Take care and best wishes,
Robert