Electric A/C unit not receiving power: fuse?

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  #1  
Old 06-02-17, 09:29 PM
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Electric A/C unit not receiving power: fuse?

Bit of a DIY noob, but willing to learn. First hot day of the yeah and the AC shuts off randomly. There seems to be no power to the entire unit. It's a combination force air gas furnace with AC, Coleman. If needed I can try find the model number. The compressor unit is outside.

I'm just a little confused as to where the fuse would be. In my fusebox I have special fuse caddies for the range, dryer and electric hot water heater, but not one for the central air unit.

However, next to the unit, there's a switch with a big box. Is there a fuse in there? Or is it one of the twist ones in my fusebox? If so... how could I tell which one it is or do I just have to remove each one, test them, and see what happens?

I'm armed with my volt meter ready to go.

Thanks! Pics below.

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Last edited by ray2047; 06-02-17 at 09:38 PM. Reason: Add images.
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  #2  
Old 06-02-17, 09:39 PM
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Is this an older mobile home? If so is there a breaker box on a pole that feeds the mobile home?
 
  #3  
Old 06-02-17, 09:46 PM
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It's a 1969 but the unit is just 12 years old. You know I never thought about there being another fuse on the outside. I know the condenser unit has it's own fuse which pops regularly when we're running the dryer and the AC at the same time. But when that goes everything else works. Any chance you could show me a picture of an example so I know what I'm looking for?
 
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Old 06-02-17, 09:51 PM
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If you don't have an additional panel outside.... my guess would be those two green fuses are what power the outside condensor.

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ON EDIT:
If the dryer is working then those fuses are ok. It would appear they connected the dryer and the condensor to the same fuse pullout. Looks like the one just under the range on the left is labeled dryer.

That single switch has a fuse under that metal cover. That may be the furnace switch.
 
  #5  
Old 06-02-17, 10:07 PM
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The big one at the top is for the range. Left is for the dryer, and right is for the water heater.

The dryer does have power. The green fuses look good. It's the middle of the night so I can't be testing fuses right now. But are you saying that the green fuses could be for the furnace / AC unit? The outside condenser has it's own mini-fusebox with flip switches. When those go out, the rest of the system still works, the fan etc. It just doesn't blow cold air until i got out and flip those switches.
 
  #6  
Old 06-02-17, 10:29 PM
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Ok well I guess the system is getting power, as you can hear the humming when that switch is on and can't hear it when it's off. What's the next step troubleshooting this problem?
 
  #7  
Old 06-03-17, 07:12 AM
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If you have a typical split system (compressor/condenser unit outside), does the condenser fan on top of the outside unit run when the thermostat is calling for cooling? If not, if you use a stick or similar object to give it a spin, will it then continue to run? This is often a sign that the fan capacitor is bad.

The simplest and least expensive thing to try are new capacitors. Sometimes they're individual units, other times they're dual units (2 capacitors in one housing). Typically, one capacitor is used for the fan, the other (larger size) for the compressor. If you replace them, be certain that the power is turned off to the outside unit before doing anything. Also, you should take a screwdriver blade and short out the capacitor terminals before touching any wires. Sometimes the capacitors retain a charge even with the power off.
 
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Old 06-03-17, 09:03 AM
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I know the condenser unit has it's own fuse which pops regularly when we're running the dryer and the AC at the same time.
What fuse.... where ?? pops ?
You have a pullout or breaker for the dryer. So a fuse blowing on the A/C system won't affect your dryer unless they are both on the same dryer pullout.

Does your furnace work to heat ?
Does the blower in the house work ?

If not you will need a meter to check for power.
If you have a battery operated thermostat.... it could need new batteries.
 
  #9  
Old 06-04-17, 08:40 AM
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No, the condenser fan does't turn on at all.
 
  #10  
Old 06-04-17, 08:45 AM
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The condenser unit has a switch on the outside of the home. It only seems to trip when something else in the home is using a high load... like the dryer, but it can trip randomly too. Maybe 5 times a month we'll have to go outside and flick the switches down then up for the condenser unit to turn back on. The blower inside the house works the entire time when the thermostat calls for cooling, but when the condenser unit outside isn't working due to the switch being tripped we obviously get no cool air.

The furnace right now doesn't work to heat.
The blower in the house doesn't work right now.

The thermostat isn't battery powered.

I do have a multi meter but am not sure where to probe to check power.
 
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Old 06-04-17, 10:29 AM
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The condenser unit has a switch on the outside of the home.
Post a picture of the switch with the internal cover off. Here is how to post pictures. http://www.doityourself.com/forum/li...rt-images.html (IIRC your last ones were way to large. They need to be 600px by 600px or less.)
 
  #12  
Old 06-04-17, 10:33 PM
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I can do that, but I know that's not the problem. That fuse trips all the time and all the stuff inside still works fine. In fact I shut it off using that switch all winter so no one would accidentally turn it on when it was covered though the winter.

But as soon as the sun comes up i'll snap a quick pic of it.
 
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Old 06-04-17, 10:51 PM
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That fuse trips all the time and all the stuff inside still works fine.
But you wrote earlier:
It only seems to trip when something else in the home is using a high load... like the dryer, but it can trip randomly too. Maybe 5 times a month we'll have to go outside and flick the switches down then up
That is confusing. If only the A/C was on it other high loads shouldn't affect it unless it is on the same set of fuses as another load and the load on the fuses is so great that it drops the voltage to the point that the amperage increases.

Or you said trip so that means it is not fuses but breakers in the box. It could be weak breakers, they do wear out but it seems they may be running the disconnect off the same fuses as the dryer. Just want to see it. Then we need to find from where and how it is powered.
 
  #14  
Old 06-04-17, 11:19 PM
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Sorry for not being clear. They are breakers on the condenser unit outside.

I don't really get why then they'll only trip if the dryer is on, maybe that's not actually the case. Those breakers have nothing to do with the dryer. But that's a mystery for another time. My primary concern right now is is to get the furnace / blower working again which appears to be completely separate to the condenser unit.
 
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Old 06-04-17, 11:45 PM
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now is is to get the furnace / blower working
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  #16  
Old 06-05-17, 01:20 AM
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Will take a pic as soon as daybreak so I can see what I'm doing. Going to shut the power off and take a peek.
 
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Old 06-05-17, 01:22 AM
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If it is just the blower hold off on that and check for a fuse for the blower as indicated in my picture.
 
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Old 06-05-17, 04:34 AM
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Outside box and the wiring behind the switch.

I'm still confused as to where the fuse is for this thing. The green ones?
 

Last edited by PJmax; 06-05-17 at 08:49 AM. Reason: reoriented pictures
  #19  
Old 06-05-17, 08:57 AM
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There is no fuse there. Someone chopped the fuseholder out of the circuit.
 
  #20  
Old 06-05-17, 09:11 AM
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So... where's the fuse? The green ones in the fuse box?
 
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Old 06-05-17, 10:19 AM
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It may be time to call an A/C repair company.

So... where's the fuse?
Follow that cable to the fuse box.
 
  #22  
Old 06-05-17, 10:43 AM
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I see my fusebox right in front of me. It has a crapload of cables attached to it and no way of narrowing it down. Should I just test all fuses one by one?
 
  #23  
Old 06-05-17, 02:45 PM
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What would be the best way to test to make sure it isn't the thermostat?
 
  #24  
Old 06-05-17, 03:47 PM
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You should be able to see where the cables go when you remove the cover. when you remove the cover.
 
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Old 06-05-17, 03:53 PM
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Actually for right now we need to confirm the furnace is working first..... so try the heat mode.

If you have a meter. Remove the thermostat from the base. Check for 24 VAC from..........

R to C (may not be a C so skip this one if no C) 24VAC
R to Y = 24VAC
R to G = 24VAC
R to W = 24VAC

You've shown us a 2P disconnect switch outside at the condensor. That needs to get power from the main panel. If you remove the panel cover.... see if the two green fuses connect to one cable. That means one green fuse would have a black wire on it and one would have a white wire on it.

I'm assuming that switch with the disconnected fuseholder goes to the furnace, You'd need to trace it to confirm. Like Ray mentioned....that switch will also connect to a fuse at the fuse box.

Without seeing the inside of your fusebox... I can imagine several wires doubled up on fuses.
A well lit picture of your panel with the cover off would be helpful.
 
  #26  
Old 06-05-17, 04:58 PM
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The furnace is not working in head mode, or cool mode. And then fan won't even turn on when I flick the switch on the thermostat to ON instead of AUTO.

Pics of my fusebox is already posted in this thread.

Will check voltages and get back to you.
 
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Old 06-05-17, 05:04 PM
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A well lit picture of your panel with the cover off would be helpful.
 
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Old 06-05-17, 05:10 PM
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Pics of my fusebox is already posted in this thread.
But not what we need. We need to see it with the cover off so we can see the wiring.
 
  #29  
Old 06-05-17, 05:16 PM
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Oh crap my bad.

I'm getting no voltage readings over any of those cables at all.

Meter set to 200 VAC. Pretty sure I'm using it right.

So that would leave me to believe that part of the furnace isn't getting power?

When I flip the switch on at that box, you can hear the thing hum so power must be getting to it to some areas. So I guess it's not a fuse issue anyway.
 
  #30  
Old 06-05-17, 06:26 PM
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If it is a digital meter check the battery by testing it on a working receptacle. To prevent damage to your meter it should be set to 300 or next highest to 300 on your meter when measuring 240 volt sources.

There is only so much we can do by remote control. I suggest you call a repair tech.
 
  #31  
Old 06-05-17, 06:56 PM
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Yeah but they generally require money and I don't have that.
 
  #32  
Old 06-05-17, 07:43 PM
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Pull the cover from your fuse box and post a picture.
 
  #33  
Old 06-06-17, 03:56 AM
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I'm not sure i feel entirely comfortable removing the cover, exposing non protected power.

Also, the furnace is getting power to some degree coz I can hear it buzzing when I flip the switch so wouldn't that rule out a blown fuse?
 
  #34  
Old 06-06-17, 09:04 AM
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You can check each fuse using your multimeter set to ohms.
 
  #35  
Old 06-07-17, 12:17 PM
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All fuses checked, all fuses good.

Scheduled a service guy, but if anyone can think of anything to check before I he gets out here I'll give it a shot.
 

Last edited by Jonathan Trillo; 06-07-17 at 12:48 PM.
  #36  
Old 06-12-17, 06:39 AM
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Little 3 amp fuse on the furnace blew. Replaced and all is well.
 
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Old 06-12-17, 11:06 PM
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That fuse did not blow out for no reason.
You more than likely have a shorted thermostat cable or exposed splice.
 
  #38  
Old 06-13-17, 11:04 PM
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It's the first time it's blown in 12 years. I'll see if it happens again then I can go from there.
 
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