Goodman model GMS80453ana. a/c unit

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Old 05-12-14, 07:55 PM
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Goodman model GMS80453ana. a/c unit

I have 2 units (one upstairs, one downstairs) with both units housed in the attic and the fans house on the side of my home. The downstairs unit thermostat stopped working (no power) where I cannot read anything on the monitor. I've switched this thermostat with the one upstairs and it will turn on. However when I put the second thermostat downstairs it wont power on.

I've checked the mother board and looked at the purple fuse and it is not discolored and still looks new. The coils are not blocked/frozen, there is not water in my drip tray and my wires connecting to the fan outside are not frayed.

On the motherboard there is a red led light that is not on or blinking. It seems like my whole unit just isnt getting power.

Is there anyway to test to see if I am getting power. Is there a tool I can purchase to check to see if I am shorting out or not receiving power to my mother board.

I am a newbie to this. However, I refuse to pay another HVAC tech and feel that this is feat I can accomplish.

Thanks in advance.
 
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Old 05-12-14, 11:26 PM
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Welcome to the forums.

Do you have a volt/ohmmeter and know how to use it ?
If you don't have one you will need to get one. Radio Shack has them as well the home depot. You can purchase an inexpensive analog meter. Handy to have around the house.
You'll need it to check for 120vac and 24vac in your system.

GOOD.......
Commercial Electric Analogue Multimeter-M1015B at The Home Depot
BETTER......
Gardner Bender 14-Range Analog Meter-GMT-318 at The Home Depot
 
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Old 05-13-14, 05:36 AM
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Thank you PJmax.

I am going to purchase one today. Thanks for the link. I have never used one. So my first question will be, does the power to the unit have to be off before I start testing the voltage on the mother board?

And as far as the thermostat is concern, I believe I read in a post that I can can check to see if my honeywell is fried?

Ill let you all know once I purchase this meter.

Thanks again,
 
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Old 05-13-14, 06:49 AM
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PJ, I purchased the first multimeter. OK. to test my honeywell thermostat to make sure that it is not just a fried thermostat, how would I do that? Also, the directions for the meter are really simple. Meaning I thought there would be more as I am confused on how to use it. I really want to test the a/c mother board in the event that there is not power at the thermostat.

Thanks in advance
 
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Old 05-13-14, 08:05 AM
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GMS804053ANA .... should be the correct model number.

The picture below shows the transformer mounted on the control board frame. Two terminals are 120vac and two terminals are 24vac.(blue and yellow ?). That needs to be checked for voltage.

You will also need to check for 24vac at the terminal strip on the control board between C and R terminals.

There is a safety switch on the blower that disconnects all AC power. You'll need to hold it in or tape it during testing.

When using your meter in high and low voltage applications..... set the meter to the higher voltage first. You can always switch it lower.

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Manual for your furnace.....
Goodman mfg Portals Info FTM-GMS8.pdf
 
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Old 05-13-14, 09:26 AM
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YOU ARE THE MAN...

That is the exact layout and exact colors. Now when I test voltage on my meter, I am aware of putting the highest voltage but where on the dial to I set it to? On my meter there is a v~ and V with a straight line above three small dashes. which side do I set it to? And what do those mean? Sorry but I am really new to this and feel that I can solve this a/c problem. DO IS SHUT THE MAIN POWER SWITCH TO THE UNIT OFF OR LEAVE IT ON WHEN TESTING?

Also, when and if my meter reads that there is power in the motherboard then is there a way to check to see if my thermostat is causing the issue being that the screen is blank.

Thank again and I promise to have more questions.
 
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Old 05-13-14, 09:50 AM
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Set the meter to V~ (that is AC volts, V with straight line/dashes is DC volts). I would suggest setting the scale to the 250V setting when checking for high voltages (120 or 240), and use the 50V scale when checking low voltages (24).

When you measure voltages, you have to have the power turned on. As PJmax mentioned, you'll need to push in the interlock switch on the blower unit to power up the air handler.
 
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Old 05-13-14, 10:05 AM
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Thank you very much Bob. I just wanted to make sure about the power. Last think I want is to fall through my floor smelling like a burnt cheeto.

Ill test the connections when I get home from work and keep you all posted. Thanks again
 
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Old 05-13-14, 03:54 PM
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Ok so I am sitting in my attic sweating small children right now and I realize. I dont know where to stick my prongs to measure the voltage... .PLEASE HELP.
 
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Old 05-13-14, 03:56 PM
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Refer back to post 5 and the picture of the board and transformer.
 
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Old 05-13-14, 03:59 PM
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Ok I got it.. I am looking at my board.. same pic you include in you post. Do i take off all of the leads that are connected to the transformer? My power is one and I have the safety switch taped off. I just dont know if I touch the red or black prong to two different leads.?
 
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Old 05-13-14, 04:03 PM
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Since you are measuring AC.... the probe colors don't matter. Check each side of the transformer. Two close together contacts and two further away.

I believe the 24vac ones are blue and yellow.
 
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Old 05-13-14, 04:10 PM
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My colors are red and blue. But none the less they are directly below the 24v sticker on the transformer. I touched the red one with one prong and put my other prong on the blue and my meter didnt event jump. If I assuming I did this right. That means I have no power coming to my board? Now in that case can't I check the power switch right next to the unit to see if power is still there. and if so. how.

once again, PJ thank you very much.
 
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Old 05-13-14, 04:26 PM
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I just tested, well what I believe is tested my shut off switch and when I opened the cover a screw from the bottom right of the switch was broken. Now there is a screw on the top right of the switch. I shut the breaker off to this unit and tested the cut off switch and I get no reading. Do you think its a bad switch?
 
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Old 05-13-14, 04:57 PM
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I stand corrected. There is power coming from the cut off switch (light switch) to the a/c unit. My wife thought it would be safer to shut off the power. I can't be mad at her for that. I still cant get an reading from transformer
 
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Old 05-13-14, 05:18 PM
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Have you confirmed 120vac into the furnace from the service shut off switch ?
Two of the terminals of the transformer (black and white) should have 120vac on them.
 
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Old 05-13-14, 05:52 PM
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OK. bare with me PJ.
Here is what I did. I tested the transformer with the 120vac and 24vac. What is did is touch each one of the ends that were sticking out of the transformer and my meter did not budge. So I test an outlet that I have in the attic and my meter flew to 120 when inserting both prongs into the vertical slits. (yeah I know)

O I then tested the power switch to the unit that looks just like a light switch. I touch the bottom of the switch once I opened it with the red prong and the black to ground it and meter bounced to 120 multiple times.

Right now I am stuck. I am thinking its the mother board but I don't know how test it other then the transformer.
 
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Old 05-13-14, 05:58 PM
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On the board you should see terminals marked Hot(H) and Neutral(N).
There will several in the H row.... there should be the incoming black wire and the black wire to the transformer. In the N row you'll see the incoming white neutral wire and the white to the transformer.

Check the H and N terminals. You should see 120vac from H to N. If nothing.... check from H to ground (metal frame). If you see 120vac when touching H and ground then you have lost your incoming neutral/white wire.
 
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Old 05-13-14, 06:16 PM
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ok ive found the terminals marked Nuetral and traced the white one back to the transformer 120V... now the H(black) wire I located by merely following it from the transformer to where it's plugged in and it reads, XFMR-H. Now remember the only electrical testing Ive done is licked a 9volt battery so when you say test, where do I put the prongs? Do i remove the wire from the transformer and the board and touch the red prong on the transformer (Nuertral white) to the Hot using the black prong?

Thanks.
 
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Old 05-13-14, 06:26 PM
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If you look at the writing on the board....there should be several H and several N pins that aren't being used. If there are no spare H pins..... then unplug the black from the transformer and check to that pin.
 
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Old 05-13-14, 06:36 PM
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I did locate 2 not used N pins and tested that by touching it to the H pin which I removed and nothing. I basically touched those pins in every way possible and meter did not jump at all. I know the meter is working cause I just tested an outlet again. Im leading to believe its the board and that'll run me 300-500 from what I read. what do you think.

Im touching each pin one at a time, then each prong touching the opposite pin etc....
 
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Old 05-13-14, 06:58 PM
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Relax.... it's not the board. The board runs on 24vac. If the transformer has no power the board will be dead.

You need to go to the service switch on the side of the furnace. You said you had 120v to ground. We need to check from hot to neutral.

Look at the following picture. That is the wiring coming into your furnace. At the top you'll see the pins you checked. You have to work backwards now out of the furnace. You need to find 120vac on the black and white wires.

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Old 05-13-14, 07:21 PM
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"You said you had 120v to ground."

Im confused... if you are referring to the switch that is positioned outside my unit that controls the overall power (bottom Pic), then yes I did get a 120vac reading when I check it which tells me that I have power in that switch but somewhere along the route the power gets lost.

The above pic (sorry I didnt rotate it) is the board I am dealing with. If you tilt your head to the left, that is what Im working with. The transformer is on top but I dont need to insult your expertise on the layout.

Now what is the service switch you are referring to?

Thanks again
 
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Old 05-13-14, 07:29 PM
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The service switch is in your bottom picture. Pull the switch out and there will be a white splice in there. When the service switch is on.... you should measure 120vac from each screw terminal to the white wire.
 
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Old 05-13-14, 08:05 PM
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Size:  33.9 KBI opened up the service switch and as soon as I removed the last (bottom) screw it popped out and a nasty spark popped. Apparently the ground wire touch another wire that became dislodged. I then noticed that the right side of the actual switch housing was cracked and a piece of the right side fell off. I also have two wires (both black) just hanging out in space and one ground wire in the bottom left hand hole in the switch.

I did find the spliced two white wires, but have not tested anything due to the sparks. Think its a smart choice to buy a new switch and where does the second black wire go. I know one goes in the top right...

see my pic below. Also the ground wire has a burn mark on it, should I cut this part off and just insert the new end. I cant flip the pic around but turn your screen and you can see the burnt piece of the ground wire and the two wires just floating.

Thanks,
 
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Old 05-13-14, 09:17 PM
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Sorry for the delay. Busy night tonight.

Ok... so you've located your problem. The new switch will have two screw terminals for the black wires. They connect either direction. You can cut a little off the ground if the wire is weakened.


If you want to test the furnace.... temporarily put the two black wires together and turn the breaker back on.
 
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Old 05-14-14, 04:31 AM
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Thanks. I hope this is my problem. I will keep you posted as I go purchase a light switch. When you put the two black wires together. Do you mean touch (twist) them together and then turn the switch on.

I still havent test the white wire to the screws yest as you said in post #24.


Thanks again.
 
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Old 05-14-14, 07:02 AM
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Ok. changed the switch. Now the split white wires (two white wires that are twisted at the end) do i need to untwist these two wires. Also when testing, Im assuming that I place the prong on the exposed wire to the white wire and just touch either of the switch screws. Ive done tested the screws and nothing.

Also to test the furnace, should I twist the two black wires together?

Thanks
 
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Old 05-14-14, 07:16 AM
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Most light switches have two screw terminals on either side of the switch. Assuming your new switch has two screw terminals on each side, connect one of the black wires to one screw terminal (doesn't matter which side), and the other black wire to the other screw terminal on the same side. Connect one of the white wires to one of the screw terminals on the opposite side of the switch, and the other white wire to the other screw terminal next to the white wire that you previously attached.

To recap, you should have both black wires on one side of the switch, and both white wires on the other side of the switch. The uninsulated (bare) wire would normally connect to the box that the switch is mounted in (if it were metal), however since it is plastic, connect it to one of the screws that you use to mount the switch to the box.

If you want to use your voltmeter to test the switch, connect one probe to the white wire side of the switch, and the other probe to the ground (bare) wire. When the switch is turned OFF, you should measure 0VAC. When the switch is turned ON, you should measure ~120VAC.
 
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Old 05-14-14, 08:17 AM
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Ok. So my switch only has three screws. One is colored green for the ground wire and then there is two on the right as you can see in the picture.

The two white wires were twisted together with one of those wire caps. I split those apart from each other and then fastened the two black wires on the right hand side.

Well I put the red prong from my meter on the black wire side and my black colored prong was touching one of the white wires and NOTHING.

I also trimmed the ground wire because it had touched a wire yesterday and sparked so i trimmed that burnt piece off.

And the white to ground did not test at all and same for the black to ground.

Thank in advance,
 
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Old 05-14-14, 08:31 AM
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Please twist those white wires back together again and put the wirenut back on.

You've found your problem with the broken switch. Make sure everything is secure in the furnace, leave the switch out of the box yet, turn breaker back on and test the furnace now.
 
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Old 05-14-14, 08:33 AM
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Ignore my previous post about how to wire the switch. I didn't understand how it was originally wired. Follow PJmax's advice and connect the two white wires together with a wire nut and connect each of the black wires to the two switch terminals (one wire on each terminal).
 

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Old 05-14-14, 09:28 AM
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OMG... THANK YOU BOTH FOR YOUR HELP.

Basically, the bottom hot wire connection to the switch box had come loose and when I flicked the switch a couple of days ago, I remember hearing something fall inside the box. It was the broken piece of plastic from the switch box. Now before this happened my a/c shut off then went back on and I am thinking it was due to the hot wire connection snapping but still maintain a sort of connection.

After changing the switch, shortening the wires a bit, I flipped the switch and the unit started up. So far half an hour the house is cooling down.

If there is anything I can do to like, applaud, make a note on your user name of how helpful you both have been (PJMAX, Bob14525) please let me know as both you maintained contact with me during my sweat fest.

Thanks again and this thread has been solved.
 
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Old 05-14-14, 09:35 AM
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Good job.....you really stuck it out AND you learned how to use a meter.
 
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