A/C Unit no power

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Old 12-26-15, 11:50 AM
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A/C Unit no power

Hello guys,

The other day my A/C unit fan keep on running and not turning off. I went to check the relay to see if that was the problem ....when I open it up I notice the white power wire has some corrosion on it. So I cut off the part that has the corrosion and rewired back it how it was (white arrows). Now the unit will not power on. I try resetting it and everything. I have not change out the relay or anything ...all I did was rewired the wires that had corrosion on it..

If anyone can help that would be awesome! Thanks guys!!!






 
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Old 12-26-15, 12:03 PM
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That red wire nut looks like it's covering an awful short splice. Since it appears it may be the neutral.... it may not be making a connection.

Do you have a voltmeter ?
Did you turn the service switch back on ?

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Old 12-26-15, 12:08 PM
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Yes i have a voltmeter. Not sure which wires to check? The wires are connected I'm 100% sure of it. Yes I put the switch back on.
 
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Old 12-26-15, 12:28 PM
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It looks like the white romex cable is the feed in. You worked on the white neutral wire. Check from that wire to the black wire from that same cable.
 
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Old 12-26-15, 01:10 PM
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i just tested it. 123v coming form the black and white wires.
 
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Old 12-26-15, 01:35 PM
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Cool. The next step is to make sure your 24vac transformer is working. You can check the transformer low voltage leads or possible at R and C at the screw connections.
 
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Old 12-26-15, 03:51 PM
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which one is the transformer? I tested the R and C at the screw connections and not getting anything.
 
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Old 12-26-15, 05:54 PM
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The door switch on those old consolidated furnaces has 2 common issues.

The wires connected to it often melt in that control box.

The section of it that is outside of the control box (that makes contact with the blower door) also fails to depress properly.

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Old 12-26-15, 05:59 PM
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so what should i be looking for? theres a metal long bar thats press on to the door. I can't open the door because the gas line valve is in the way. any help would be great!
 
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Old 12-26-15, 07:09 PM
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Running the gas furnace with the blower door removed can create a dangerous condition so the manufacture provided a door switch on (only) one of the two blower doors.

I have seen a folded piece of cardboard holding in this door switch more than once. I have also seen this door switch bypassed. Consolidated is no longer in business so I am not sure where you could get a new door switch but it is possibly still available.


Place the fan to the On position instead of Auto at the thermostat and push the switch in to see if the fan will run (proving power).
 
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Old 12-26-15, 07:20 PM
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Yes the fan run when i hold down the metal switch. When i let go it turn off.

 
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Old 12-26-15, 07:24 PM
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It just popped out.

It is a spring like material. Just slip it back between the door and the furnace.

A flat screw driver in that gap can make it easier if it is a tight fit.


On another note...
That furnace requires regular cleaning. The burners can collect several pounds of rust on top and cause the flames to burn improperly ( like dumping a flower pot of dirt on top of your stove in the kitchen)
 
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Old 12-26-15, 07:32 PM
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I've always seen it like that. It don't fit in the gap.


Where do i clean the top of the burners?
 
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Old 12-26-15, 07:41 PM
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the switch looks like this from the inside.

[ATTACH=CONFIG]60555[/ATTACH]

http://s3-media3.fl.yelpcdn.com/bpho...jE0Ew/348s.jpg
 
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Old 12-26-15, 07:46 PM
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Sure seems like a straight screw driver in that gap should open it enough to get that thin piece of metal in there but...


I would turn off power and gas to the furnace, remove the three 5/16" screws holding the burner cover, remove the two 5/16" hex screws holding the second burner door under it, loosen the flax gas hose, remove the wires to the gas valve, (take a picture of them first),remove the burners and dump the 2 pounds of rust onto some news paper or a trash bag, remove the blower door, measure the capacitor and oil the motor, verify that the squirrel cage doesn't have any large debris in it then put everything back together. ( making sure to put the door switch back) and use some soap bubbles to check for gas leaks where you removed the flex connection.

Observe the flames burning before replacing the two burner panels.

A pro would also be able to run a carbon monoxide detector around that old furnace.
 
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Old 12-26-15, 07:56 PM
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Thanks for all the info and advice...I did what you said and its working now. Will this also fix the fan issues? It was keep on running and not turning off.

How safe is it for me to clean the burners?
 
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Old 12-26-15, 08:00 PM
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I was trained.

The fan limit is probably old and sticking.



Some models have a white plastic pin that will not allow the fan to turn off if someone bumps it in.
 
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Old 12-26-15, 08:07 PM
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okay im looking all over the unit..I don't see any fan limit. Where would it be located?
 
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Old 12-26-15, 08:15 PM
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There is a pipe running from the control box in your first and second pictures.

This pipe will run to the fan limit.
 
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Old 12-26-15, 08:21 PM
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okay I see a metal box... have to open it and check it out. The fan seem to be working right now. It just turned off by it self. I will put the fan limit on notice if it keeps running and not going off.

Also How safe is it for me to clean the burners myself?



Thanks so much for your help Houston204 and PJmax! =)
 
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Old 12-26-15, 08:55 PM
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Remove 5 hex head 5/16 screws and take a look at the burners.

You have a spark ignition model so the burners may not be too bad.

A shop vac may be able to clean the burners if you have a build up of rust.
 
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Old 01-01-16, 05:41 PM
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yeah the fan keep on running. I have to tap the fan limit for the fan to shut off. My fan limit looks just like the one on right picture. Can i fix it or do i need to replace the whole thing?
 
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Old 01-01-16, 05:46 PM
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You need to replace it.



The bi metal probe comes in different lengths.

I usually get that length and the part number.

I wouldn't buy that part without removing the 2 panels that cover the burner section and watching the flame burn. If you have a nice blue flame then pick up a new fan limit.

If the flame looks like blower air is blowing on it then you have a bigger problem.

It is obvious when the blower isn't running until after the burners are lit.
 
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Old 01-01-16, 07:55 PM
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1st what is a bi metal probe? Do I need to replace that also and how do I find out whats the length is?

Can i just replace the fan relay/limit?


What do you mean if flame looks like blower air is blowing on it ?

Do know know of any youtube videos of the flame issue your talking about?
 

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Old 01-01-16, 08:19 PM
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Your fan limit has a pipe in the back that sticks 5,6,7 or 8 inches into the furnace.
It is shown in the left fan limit picture that I have already posted.

If you have an inspection panel between the furnace and an evaporator coil it is usually easy to measure the length of this pipe.

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Your furnace will have 3 hex head 5/16 inch screws holding this panel. It may also have a safety switch here.

There will be another panel behind it.

If you remove these 2 panels and verify that you don't have several pounds of rust sitting on top of the burners.

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Give the furnace a heating demand and watch the flames. They should be blue.
The blower will start after the fan limit hits 150 degrees and the flames will turn yellow and blow around as if you blew on the flames if you have holes in the heat exchanger.

Having this furnace professionally inspected might be a good idea.


You might Google consolidated furnace and class action lawsuit.
 
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Old 01-01-16, 08:40 PM
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okay i see....the bi metal probe is a part of fan limit. for me to see the probe i need to remove the limit 1st.

can i replace it with a newer Model Fan and Limit Control? Should i replace it with something like this... click on link below...

http://www.amazon.com/Honeywell-L406.../dp/B0009726EW








 

Last edited by SoildSnake; 01-01-16 at 09:12 PM.
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Old 01-01-16, 09:08 PM
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Yes.

The fan limit information is on the side touching the white hardcast tape.
 
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Old 01-01-16, 09:26 PM
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why does the door have a hardcast tape on it? its okay for me to tear the tape off?

Its a Honeywell L4064T1848. Whats the newer model of this that will fit? Do i need to remove the limit 1st and see what size the sticks is... 5,6,7 or 8 inches ?
 
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Old 01-01-16, 10:01 PM
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MARKAL Zoom Spout Oiler,4 Oz - Oils - 4NA76|79704G - Grainger Industrial Supply

I would cut the hardcast tape. It is much better than regular duct tape. You only want access to the motor. The furnace can still be sealed to the return air duct. The motor may be behind the opposite panel.

The motor probably has an oil port on each end. It is tough to get the back port without a zoom spout oiler.

Checking the capacitor is also something that I would do while in there.
http://www.amazon.com/Uni-T-UT210E-C...rds=uni+t+210e


I saw one site say that the fan limit is 8 inches long. If I saw several sites agree with this statement I might feel comfortable spending over $100 on a new part but I didn't.
I would measure it.
 
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Old 01-01-16, 10:11 PM
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whats the Zoom Spout Oiler for? Okay so let me get this all straight...

1) Remove the Fan and Limit Control.
2) Measure the metal probe.
3) buy a new limit with the same size probe.

Can I buy any model of the Fan and Limit Control as long as its the right size probe?
 
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Old 01-01-16, 10:22 PM
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http://www.amazon.com/Honeywell-L406...064T+fan+limit

If you have an 8 inch probe I would get this one. You will need to remove a tab if you are breaking low voltage when it trips.

A close up of the diagram will probably reveal this to be the case.

Many of the original motors in those furnaces have oil ports.It is hard to reach the back port without the right oiler.

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Old 01-02-16, 08:11 AM
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Old 01-02-16, 08:16 AM
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Yes.... that is the correct oil and oiler.
 
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Old 01-02-16, 09:44 AM
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what do i need to test with the Uni-T UT210E True RMS AC/DC Current Mini Clamp Meters w/ Capacitance Tester?

looks like an 8" probe. I get this one on amazon correct?
http://www.amazon.com/Honeywell-L406...=vglnkc4130-20

 
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Old 01-02-16, 10:27 AM
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Yes the 8" model will be fine. That is a great price. I paid $125 for the last couple that I picked up.

The clamp meter is able to check capacitors, and can check the amperage of your motor. If you wanted to check these items it would be a good choice. I use mine several times a day.
 
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Old 01-02-16, 10:40 AM
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Thanks bro...can I check the capacitors and amp of the motor with a multi meter?
 
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Old 01-02-16, 11:04 AM
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It is possible that you can check the capacitor. What meter do you have?
 
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Old 01-02-16, 12:27 PM
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Old 01-02-16, 03:33 PM
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Yes that model will measure up to 200 microfarad. Your run cap will be between 5 and 15 microfarad. 15uF Turn it 3 clicks clockwise from off. The icon looks like 2 T's head to head.
The icon is usually a polarized symbol but your meter has a non polarized symbol.
It makes sense since these are non polarized capacitors.

polarized symbol...


Some models allow you to manually select the range of nF,uF, or mF.
We use uF which is millionths of a farad or microfarad.



A current attachment is available that would allow you to measure the motor amperage and compare it to the motor rating but it is usually difficult to see the motor FLA rating because of the belly band on the motor that mounts it to the blower.

http://www.amazon.com/MASTECH-MS3302...TMQW6ZSTP5SWGQ

The capacitor should read plus or minus 10% of rating. If a 10uF cap reads 7.5 it should be replaced even if the motor is able to start. The running amperage will be higher if the cap is weak and it will not give you reliable operation.



I miss the days that outdoor units used an additional panel under the panel for the controls.
This old GE panel looks cleaner than modern units that are still under warranty.

 

Last edited by Houston204; 01-02-16 at 04:07 PM.
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Old 01-02-16, 10:17 PM
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okay so I turn it 3 clicks clockwise from off...then check the mounts capacitor correct?

can you link me to some youtube videos so i have an idea what you guys are talking about?
 
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