DGAT070BDF Fuse Blows

[mrfixit64857]

First of all, thanks for the site! Great info I have picked up on in here!
My DGAT070BDF is under a recall. I didn't know this until this problem arose, so the problem may have saved a life. Still, I am a man of limited means who is forced to do much of his own work, within my limits of course.
I must confess, I blew it. I read another post where someone else did a similar thing, and that has given me the courage to admit my own error here.
I was cleaning and working on the furnace when I noticed a few of the wire connections were poorly taped. I'm a strong believer in WireNuts on these type of connections so I unravelled the tape on the connections and went after my wirenuts. I set the box there by the connections and it didn't want to stay, so it tried to fall. I grabbed at it, and in the process two of the bare connections, a RED and a WHITE, met each other and there was a nice bright spark... but short-lived. All of a sudden my furnace's little green eye went dark. I looked the board over and found a 10 amp blade fuse had blown. Back to my supplies, found a replacement, put it in and turned the side switch back on. I noticed little whiffs of smoke coming out of the back of the board in the upper left corner, so I flipped it back off right away. I took my flashlight and began further inspection of the board, and noticed that the fuse I replaced was SUPPOSED to be a 3 amp, not a 10, even tho that was what was in there since I have had it.
My question is this: What could I have toasted on this? As I mentioned, it was the RED and the WHITE connections that come from the board's upper left corner that got crossed. If it may be the transformer, how do I test this, without powering up the board and causing further damage? HELP!

[Robert]

Hi ,


That is the Red power wire to t-stat and white heating wire from t-stat back to the board.


Go to transformer and test across the 24VAC secondary LOAD side for 24-28vac.


It may have fried the transformer or possibly the board since it had wrong fuse installed.


If the transformer is ok, good chance it ruined the board.




Thanks,
Robert

[mrfixit64857]

Thanks, Robert! I;ll do that when I get home.
Just to clarify: if I remove the fuse and power up, does that energize the transformer so I can test it?

Thanks again,
Tom

[Robert]

Turn power to furnace OFF. Just remove the wires after marking where they go from the LOAD/SECONDARY/24VAC side of transformer.

Turn power ON.


Then using a multi-meter, place one lead on one terminal and other lead on the other terminal.



You are testing the transformer for 24-28vac.



You can remove the fuse from the board beforehand.



IF you do not read 24-28vac, then test across the other LINE/PRIMARY/120VAC side for 120vac.



IF you have 120vac across LINE side and do not have 24-28vac across LOAD side, transformer is bad.


IF you have 120vac/LINE and 24-28vac/LOAD, then most likely the board is toast.



With the 10amp fuse, it allowed 7 more amps than designed for before it blew the fuse.


That most likely fried the board.




Thanks,
Robert

[mrfixit64857]

Thanks. I had tested it this afternoon, and the transformer seems to be still working fine, putting out 26.4 VAC.

I have seen this board on sale for about $177. Is that a fair price for one?

Also, since day one, this furnace has had a "Hum" to it, and it seems to be coming from the back until I touched the transformer today... that made the HUM go away, lol!
Is this just a harmonic byproduct of the transformer, or is it a sign of bigger problems?

Thanks again for letting me pick your brain on this.
Tom

[Robert]

Hi,


Integrated Control Board # 7990-320P @ $172.00 + $8.00 shipping .


This is our every day price.


It can be seen and ordered from here:


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




Scroll down left side to locate, click on pic for enlarged view.



If interested, please add to cart and order through PayPal or call toll free to 1-877-263-7860 after 9AM CST M - F and charge to Visa or Mastercard.


I would be sure board is in fact bad first before buying. Could be further damage in area of smoke.


You're very welcome, glad to help.


Thanks,
Robert

[mrfixit64857]

Yes, I was planning on tagging all the wires and removing it to have a look-see before I buy, and I need to wait til payday anyway

Thanks!
Tom

[Robert]

Hi,

You're very welcome. Look for burnt spots or brown signs of overheating.



Take care and best wishes,
Robert