Question about Goodman GMS90703BXA Heater

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Transformers and fuses keep blowing

My Goodman heater has had 2 transformers and 4 fuses replaced in a month and the technicians can't figure out why the transformers keep blowing. One time it blew the transformer and not the fuse another time it blew a fuse one day and I had that replaced and then it blew the transformer the next day. All the wires have been tightened each time and we still can't get any long time resolution. Please help. Tonya

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  • Anonymous Jan 27, 2009

    I have the same problem, I just blew my fifth transformer. I had a sears tech install a new relay. I think the relay is the coil. is the relay the coil? How do I test the coil to see how many amps it is drawing? I have tried many types of transformers. I know s omething is causing them to blow. This is number 5 today!



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If you are where it's warm and you are using air conditioning, have the technician check the coil in the relay in the outdoor unit. I replaced 2 transformers before I figured out the coil was shorted out and drawing too much current.

Posted on Jan 04, 2008


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My air handler is blowing the 3 amp fuse on the curcuit board. what does it control

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so you seem to know alot or enough to get by on this oven and you have the testing equipment clearly since you gave me the amp reading.

17.25 is just a little to high. Which is prolly why your having a hard time figuring out the problem. The next thing i would check would be the HV transformers. One of them is prolly pulling just to much. They should be somewhat even.

Discharge the HV Cap before continuing
Unplug the wire coming from the first cap to the transformer at the transformer and then energize the mag current record your amps

then plug that one back in and repeat for the other cap and HV transformer

hopefully you will notice a big difference in the amps between the two transformers

if that didn't work you will need to measure the windings of each transformer of which turbochef will give you this info

Also if the oven is working in test mode but not in a true cycle. Run it in a true cycle. Clamp your meter on then power up the oven and run the cycle that blows the fuse. See if the amps spike before the fuse blows

These fuses are expensive, too expensive to be blowing testing the oven. Bring the fuse to home depot and buy a bunch from them. There not an exact match, they will be a little short but will work for testing purposes. Once fixed buy the proper fuse from turbochef there around 10 bucks each

Good luck and don’t get down that you replaced those parts and its still not working. Most repair company’s replace all those parts anyway. Your typical bill to fix this problem is around 1800.

Oct 22, 2009 | TurboChef C3 Single Oven

1 Answer

Burning up transformers

YOUR the first person that has gave enough information to help in a WHILE THANK YOU SO MUCH!!

Start all over from first
I'm betting that you need a fuse in both sides of the transformer until you find the real reason they burn up.

A solenoid valve that sticks can cause the transformer to blow but so can a lot of other things, namely anything in the control circuit that uses the 24V power. A relay or contactor that doesn't pull in or a defective defrost control, a shorted wire from the thermostat.

I'm wondering if you have what we call a package heat pump meaning the both the indoor blower and out door compressor & fan are in the same section out side? OR is your a split system with an indoor section and an outdoor section?

I'm betting on the split section. In some miss-matched systems (like a Lennox indoor and a GMC out door for example) Some of the origonal Lennox heat pumps had an out door and an indoor transformer. If these trans formers were not "phased" together it could cause a problem like your having. Now you just have it in the heatign mode if I read between the lines correctly. So it makes snece that it's something with the heat. The out door unit can opperate withits own 24v but if you have back up heat inside (gas or electric Im thinking you have electric) the indoor section will come on atfter a few more degrees of heat loss (2-4'F). This is where the transformer inside will buck the one outside and somethjing has to give. The weakest point.

From what ive been told by some of the old hands I've been around if the high volt side burns out look for a low volt problem if the low volt burns out look for a line volt problem.

If this has 2 transformers like I suspect try the fuse on both sides but remember the one is hot and will remain hot all time on 220V or 1 leg of it or it might remind you. To phase these transfoprmers I believe you swtich the main lines L1 & L2 at either of the transformers. Now 1 more thing the indoor section may be using ground on the low volt side as a path for 1 side of the transformer. I believe you will ahve to do same for the other transformer too.

Hope this helps Id really like to know what you find and do.
Please ask more and you give such detail I can follow you with little trouble. Please rate me as high as you can and good luck.

Mar 30, 2009 | Goodman Heating & Cooling

1 Answer


you obviously have an intermittent low voltage short. I would visually inspect all low voltage wiring to try to locate the problem. Pay good attention to the limit circuit, I have seen wires melted to the inducer housing before causing this problem. also, install a 3A fuse inline till you find the problem to save on transformers.

Nov 25, 2008 | Dayton Heating & Cooling

2 Answers

BenQ FP72G+ 17" LCD Monitor NO DISPLAY

The way the circuit works is in a mirror format. There are 2 identical circuits that go to each end of the board.

Be sure to check that fuse for continuity, not just for a second like you normally would, but hold it for a good 10 seconds.
Also don't forget while you are in there it's best to repolace it anyway with an actual fuse. A 3A slow blow ceramic is good for this.
Check the 4 transformers as well, if you notice the top circuit is the faulty one, then check the transformers at the top. The transistors are quite powerful, and normally need something to trigger them into failing. Do the same for the bottom circuit.

This monitor came in 2 formats. One with 4 transformers and 4 CCFL tubes, one with 2 transformers that lead to 2 CCFL connectors powering 2 tubes each (3 wires per CCFL)

When you order the 2SC5707's get extras just to be on the safe side. If it goes again, then turn the monitor off immediatly and check them. It should only be 1 failed again, so just see which of the 2 transformers it was primarily attached to and replace it, or both.

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3 Answers

Goodman GMS90703BXA Heater/AC - 3 Amps Fuse blows

This fuse is used on the low voltage side of the furnace. All 24 volt controls operate thru it. You may have a short in your thermostst, thermostat wire or even a bad transformer. After replacing the fuse, inspect the wiring in the cabinet as well as the wire heading toward the thermostat for damage. If you find none, check the thermostat for loose wires or contacts. If all else fails, jump out R and W with a small jumper temporarly at the furnace and see if the unit runs. You will have to tape the door switch closed to run it with the panel off. Remember, this will keep the furnace running 100% of the time until you disconnect the jumpers. Not a solution, just a test! If it runs flawless, you have a bad thermostat or wire. Diagnosing a transformer is for a technician.

Aug 12, 2007 | Goodman GMS90703BXA Heater

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