Lennox P-8-9490 Transformer Burned Out
Two days ago I discovered my AC no longer working. The house thermostat indicated it was not receiving any voltage. I traced this back to the blower transformer which was not sending out any voltage. Input to the transformer was proper (110V).
Yesterday, in a pinch because of the holiday, I installed a Honeywell 25V 40VA transformer which I expected to work until I could get a replacement P-8-9490 transformer. The Honeywell also burned out. Is there any reason for the Honeywell to also burn out?
View related: Lennox 80MGF Board Burned out2011-12-05 23:17:39My Lennox 80MGF EGC-2 Board burned out on my 1997 Lennox furnace. I have had the board replace once before by a pro.
This time, I am thinking of replacing the board myself. I was able to get my hands on another EGC-2 board and that should be arriving any day.
Besides the obvious - labeling wires and making sure all wires are correct, is there anything else I should be concerned about?
I will keep you posted once I get it installed.
How to diagnose a short in the outside AC unit2011-10-29 01:33:19Hi,
My furnace transformer burned, i proceeded to replace it with a new one with a fuse included, the transformer turned on but the fuse blwq immediately after turning the AC on. I verified the outside control cables connected to the contactor of the AC, and noticed that they were shorted. Inspected the contactor which was burned.
However I also noticed that the resistance of the compressor is very low as well, as the multimeter beeps for continuity on it. Is this normal for the compressor?? Or does this mean that the compressor is it the culprit of all the trouble??...
wiring furnace transformer2012-10-26 21:51:45Hi all, I am trying to install a new transformer on my furnace and well the new transformer does not have the labels my old one did, COM , COM , 120v, 24v. Here is a picture of the transformer it only shows LOAD, LINE but doesn't specify which lead is exactly what.
Also I have attached a second picture of my old transformer.
Thanks for any help....
Wiring trouble2012-03-22 19:37:14I have a Rheem heat pump unit that burned the 24VDC transformer out. I replaced it and burned the replacement up. I replaced it again and took a 3 amp breaker and placed it between the thermostat wires and the outside unit. I found that 1 of the wires that goes directly from the thermostat to the outside unit trips this breaker when I start the unit up. I tested by running new wiring and found that the wiring is okay. But I do not know what is causing the problem. Is it the thermostat or the board in the outside unit? Any help would be greatly appreciated. I have a 6 wire heat pump thermostat. Wire is Y that is giving me trouble....
Need help testing RTU transformer (Pics)2012-11-29 21:36:19Hi there,The problem: I have no power to a 1H/1C thermostat. I have checked the whole wire for a splice, short, etc and the wire is good. I have tested power with a multimeter to the red power connection and the green blower connection, and have manually spliced the power and blower wires to at least kick on the fan. Even with it spliced, it will not turn on the fan - The unit will not kick on.What I have done: I have tested power on the roof top unit (It is a small carrier model) from the power in to the contactor and I get 120v on both sides of the contactor. In addition, I can manually kick on the compressor on this contactor (not going to do me much good as it is -22 celcius out). What I wanted to do was test the high and low side of the 24v transformer, which usually is not hard for me to do on the Lennox models we have here (90% are Lennox) but I'm unsure about this carrier, as it is different.
The carrier model is a 48-SS 1 heat 1 cool.What I need an answer to: Am I correct in starting my search at the transformer?
Based on the pictures below... What the heck do I do???
Replacing Inducer2011-12-06 09:09:06I have an old Lennox vertical furnace where the Fasco (No. 7121-8774, 25J1201) motor has burned out. I see where I can purchase a new one for around $120.00 but don't have any experience in replacing it. It has a simple wire connector but I am not sure if it will pull straight out after removing the 3 nuts or if there is a trick.
Trane X1000 120/24VAC Transformer2011-11-15 17:47:22Guy's I have a problem that I need your help with. The 120/24 VAC transformer primary side was shorted, so I first thought maybe something was wrong internally, but I found no shorts. I replaced the transformer today but check for any shorts before doing so, turn the heat on and everything was good, or so I thought. I went to the store and came back to find the new transformer shorted on the primary side too. I removed the transformer and checked with my multimeter and found nothing shorted. What could cause 2x transformers to go out? It was working fine, no problems. Any help is appreciated....
(Wiring Problem) Switching from MARS2 Control Transformer (CT) to PROTECH CT2013-06-22 15:53:46First, I would like to thank you for reading my post. Second, my MARS2 control transformer finally gave out, which, of course, stopped my entire HVAC system from working. However, when I went to the hardware store to purchase another control transformer the only kind they had was a PROTECH model.
The PROTECH model has a different wiring scheme from my previous transformer and therein lies the problem which lead me to you.
Originally, my Mars transformer was connected to color for color (Blk to Blk), (Blue to Blue), (White to White) and (Yellow to Yellow). Also, the red and orange wires weren't connected to anything but where taped off at the end.
However, my new transformer has almost the same coloring scheme BUT it has two yellow wires and I have no idea what to do with them.
Lennox AC won't start2012-08-01 07:40:59I have a Lennox AC unit HS23-311-2p , the other day it just stopped working I've checked the connectors from the thermostat to the furnace to the unit and all are okay. I have continuity in both fuses in the outside box as well as the indoor fuse box. I then found a burned wire on the red wire connected to the start capacitor, I have replaced the wire and have power running through it. I haven't checked the connector at the fan motor or the compressor but I don't hear anything. Before tearing the whole thing apart and checking the connection at the fan and compressor is there anything else I should try first? Thanks for all of your help!...
transformer failure in a Trane XE782011-11-28 02:37:39I have a Trane XE78 furnace that has blown the power supply transformer. The primary windings were shorted in the original transformer. I replaced the transformer with the same exact on and it went out right after attempting to turn the A.C. on. With the A.C. off the light came on the board like it should.
I checked the blower fan with a separate power source and all speeds are working fine. I opened the control board cover and there are no visible bad parts. Can anyone point me in the right right direction? Thanks for your help...
Lennox G26 Furnace2011-11-30 02:47:25The furnace control board has no activity on it's LEDs. I have no command of heat, cool, or fan. I started with resetting the breaker, then tried a new digital thermostat. I also tried attaching the thermostat to the furnace with a new piece of 24' wire to try and eliminate a short. I checked power to the door switch and checked fuse and all seem good. I have the same power input level from door switch to circuit board to transformer line in. I have zero power coming out of the transformer load. I have tried a new circuit board which bought me to a new model 83M00. This replacement board has a yellow/green wire that is extra, there was nothing in the install directions regarding this wire. I have also tried a new transformer. What seemed like an easy, logical fix has not turned out to be so. Any suggestions would be appreciated, I don't think our space heater is going to keep up with the arctic chill headed our way. Thanks....
Troubleshooting a Goodman Integrated Control Mod2011-11-29 16:57:04The fuse on integrated control module in a goodman model GMT blows almost immediately when replaced in the AC mode. I have check the 120/24 transformer with an ohm meter and it reads no short to ground on either side and the opposite poles are isolated. The board shows no 'burned' components or spots from the front. Are there another tests that I might do before replacing this module?...
Lennox Furnace Dead2011-10-27 11:13:22Son has a 2 year old Lennox G50UH series furnace that will not fire up.
Thermostat has new batteries.
There is power to the furnace, from the make up box, through to the transformer.
The gas valve is 'on'
Mini breaker next to cover switch is not popped
Both LED's are out(red and green).
It worked fine the first year. Last year it wasn't used and the gas to the house was turned off. House was heated with space heaters due to idiocy of occupants.
Poor diy'er guy!2012-09-18 05:46:15Service call today. Home owner attempting some maintenance on his a/c unit to save some money changed the contactor on the condenser, connected the low voltage control wire to a 120 volt line, fried the furnace control board, the transformer and the thermostat.
$600.00 is what he spent for not asking first.
I should've taken a pic of the white condenser wire. It had no insulation on it left, burned right off all the way to the furnace....
HVAC transformer2011-11-13 17:37:17Hello. I have a carier package unit on the roof. The transformer is fried. primary side requires 230V . black and orange . I have no problem understanding this but,the transformers secondary side puzzles me somewhat. this one has 2 posts with 3 terminal connections, on the side of the transformer. The wires that add up to 6 wires.I'll explain: two terminals posts for 3 wires each. A set of 3 black.One goes to the Compressor contacter. Probably coils. One down to a large spark valve.The second post with 3 wire terminals are orange and white. they are clearly 24 v. one wire of this termiinal connects to Thermostat 24 v. wire. this is a 304960-702 Transformer. Sorry for being long winded. The sub for this Transformer is a TRA01BD208A. With a price tag of around 60.00. I have two questions. can i use a PF32440 Transformer Use the Primary side option of 230V Orange Blk. And on the secondary side connect the 3 Black wires to the Secondary blue transformer wire. And the other set of wires orange ect. to the yellow secondary transformer wire. and be done with it???Any help would be appreciated. Thank YOu....
Heil heat pump not working2011-11-16 18:38:33Thought I posted this yesterday but could not find it. If so sorry for the dbl post.
I have an 8 year old Heil 5 ton Heat pump. I replaced the fan blower motor two years ago and the condenser fan motor this past year. All capacitors were replaced when the motors were. The compressor will not come on. The outside condenser fan will not run. The inside fan operates normally and blows air thru the house. Thermostat is a Honeywell deluxe programable (also 8 yrs old) and appears to be operating normally. When operated in the heat mode, thermostat is calling for aux heat. Aux heat strips are not being energized. I believe this may have been happening for several weeks although I did not make the connection until this weekend when the fan stopped working.
Power is reaching the contactor and when manually pushed in to make contact, the compressor and outside fan operate.
Update: Checked for 24 volts low side of contactor. 24 volts - good. Placed jumper wire from low voltage side of contactor to Y1 on low voltage Thermostat bus. After timed delay, compressor and fan came on. Doesn't that indicate a Defrost board pbm?
There appears to be no obvious burned out part. Transformer and Sequencer appear normal. Defrost control circuit card appears normal with no burned spots. There is no burned wire or other smell.
Any idea what might be wrong? My first thought is to suspect the Contactor as the system works when it is manually operated. However I am not sure that is all there is to the issue. Help please....
Carrier 40aq024300BU (V)?..transformer2013-01-19 06:39:34I need to replace a blown transformer on a carrier 40aq024300BU....anyone know what the part number is, where I can find one? Thanks. Also...anyway to get the system running for heat! Here are the numbers I got off the old transformer 308346, could be 303346 hard to read. 60VA 24 volts Model number 40AQ024300BV Serial number:53A58192...
mgb100hd2011-11-10 06:32:04can someone tell me how to test a transformer on a utica boilers mgb100hd
pilot light is good but wont fire up
i clean the flame sensor and still don't fire up
now im looking at Faulty pilot gas valve or transformer i try to test the transformer and it just read 1 on the meter i dont know if i did this right or not need some help...
Condensor won't turn on. Need opinions2011-11-30 06:56:54I have following problem: When AC is on - contactor makes noise and wouldn't latch. I tried direct voltage from drill battery and it would latch evey time with 18V.
Anyway, I thought it's contactor and got it replaced. Didn't help.
I started to check beginning from transformer. Took direct wire from transformer to the contactor - CLICK
Shorted wires at thermostat - CLICK
Bingo! Thermostat is bad. Replaced.
Yesterday I got a call from tenants with the same problem
Now I'm thinking it can be either wiring or transformer.
Reason I think transfromer is because in a winter plumber did a short on control wire and transformer fried. I used transformer from humidifier but I guess it may not be rated enough?
What else should/can I check? It's a straight AC, everything is pretyy simple and I can't see what else might be wrong.....
Trane XE 80 burn my 120 to 24V transformer2011-11-05 14:14:22Yesterday I came home and found that my indoor unit burn the transformer. I installed a replacement but the A/C wouldn't work. After a few minutes I noticed a burn smell coming from the unit, I immediately unplug the unit. Today I went ahead and tested the transformer with everything off. It was giving around 26 volts. I went ahead and fused the secondary side with a 1.5 amp fuse. When turning on the fan alone it works fine. When positioning the thermostat in heat or cool, I blew up the fuse right away. I took off the fuse and repeated the process using the door switch so I could get the power off in a hurry, I get a small buzz sound from the transformer and the voltage reading drops to around 8 to 9 volts. At the same time the transformer starts getting hot. I check the outside unit (heat pump) contactor winding and is not open. Any suggestion will be appreciated. I also bougth a new transformer but not using it since the first one tested good without major load on it....