Problems with Evcon 7681-8191/2 gas furnace

[keith]

Lost power last weekend due to the ice storms and now my furnace isn't working right. Set the temp to 73 (inside temp in the 60's). Pre-blower motor(?) fires up, igniter lights up and the fire kicks on. When the main blower turns on to send the heat through the duct's the fire goes out (shuts off). The system kicks off and won't start back up unless I turn it off and back on at the thermostat. I did replace the thermostat, but it's still doing the same thing.
My fingers are getting numb from the cold and I could sure use some rescuin'! Please, any advice you can provide will be appreciated. More snow and cold expected tonight and we need some heat.
Thanks in advance.

[Robert]

Hi,

Look on front furnace facing for a data lable or paper sticker with furnace model number.


The Model # you gave is your Blend Air model number.



Thanks,
Robert

[keith]

Sorry, it's DGAT090BDD.

[Robert]

Is the diagnostic bulb on circuit board in control box flashing any code ?



Thanks,
Robert

[keith]

No sir. The light is dark. I will reset the system and let you know the result.

[keith]

I think I may have found the problem. When I removed the CB cover, there was one wire that looks to have been pinched between the board and cover. It has a smooth spot worn in it, but not to the point of exposing the copper. It is a purple wire, 2nd from the left in front of the fuse. I've taped it, repositioned it and closed the box cover. The system has run three cycles without incident.

Do you think this may have been the culprit? Or could it have been something else? I'm guessing if there was no flashing LED then there must not have been a real problem (just an intermittent short)?[/img]

[keith]

Hang on, after three successful cycles, it started flashing three times. Temp is 71, setting is 74 and it's not kicking on.

[keith]

Ok, it's run 4 or 5 cycles without incident, then it clicks, the light begins to flash three times and it won't start back up unless I turn the heat off at the thermostat. Once I do this, it cycles again for 4-5 times. When I went to put the cover back on the control box, I pushed some wires over to fit it back on and it seemed to "short" the motor or something, but when I let them go, it resumed it's start up. Whadda ya think? I've got a little voltmeter tester thingy but not sure what I need to check...I'm no Toolman Tim, more like his retarded brother, but don't tell my wife, she thinks I know what I'm doing!

[Robert]

Three flashes indicates a problem with the centrifugal switch inside the booster motor.

IF the booster motor is running, then it's most likely the switch.

It is either starting to stick open or stick closed.


It cannot be bought seperately and if it's bad, will need to replace the booster motor.


The pinched wire could be a secondary problem as well.


Can give ordering info on booster motor if needed.



Thanks,
Robert

[keith]

Please, I would appreciate it. There are several parts stores here in OKC that might carry it (?) all I need is part/model number. Any ideas for the price range? What about installation, do you have instructions/information that might assist?

I greatly appreciate this forum and your assistance.

[Robert]

7990-317P/A @ $107.74 + $10-$12 shipping. We give help on DIY installs where safe and when purchased from us.


It can be seen and ordered through PayPal from left side here:

http://www.mobilehomerepair.com/ColemanGas.html


If in Canada, let us know for added info.


With the way yours is intermittantly working, could be the contact points are becoming pitted, thus it is now intermittant.


The way it was going out when blower motor come on may be due to a wiring problem.


Before spending possible unneeded money, would be best to thoroughly test and make sure it is the centrifugal switch or a combo of two problems.



Thanks,
Robert

[keith]

Ok, Thanks. How's the best way to test for both issues (contact points and centrifugal switch)?

Thanks again,
Keith

[Robert]

You test to be sure motor is getting 120vac and sounds to be running fine and full speed.


If so, then test to see if the two wires coming to centrifugal switch has 24-28vac coming to it and then coming out.

ONE of those to ground will read 24-28vac and IF the cent. sw. closes, the other will then read 24-28vac to ground.


Any wires in control box that change operation when moved should be replaced.



Thanks,
Robert

[keith]

Thanks, I'll check it tomorrow and let you know what I find out.

Thanks again. I do appreciate it.

[Robert]

The contact points are inside the centrifugal switch, so they are one and the same.



You're very welcome.



Take care and best wishes,
Robert