A/C problem, need help ASAP

[Noon-Air]

Ok, lets say that you *DO* figure out what the problem is... do you have the correct parts on your truck to actually make the repair?

[mm]

I am an amateur, but...

At this stage I don't think you should be trying to measure amps, and since it is wet, I don't think you should be trying to measure volts.

You should turn off the breaker so that all hot leads to the compressor are disconnected, and when you verify that there is no voltage, you can start measuring ohmage, resistance btween the hot and hot, or the hot and the ground, in your compressor.

First realize that there are two power supplies to the compressor, a

110 volt circuit that uses the thermostat and the control board to control the contactor, probably the thing you heard humming below, and a 220 volt circuit that actually powers the compressor.

BOTH CBs should be off.

Everything below assumes that the problem is in the 220 volt circuit. If that's not true, post back.

If you got 200 amps, and even if you got less, but it kept tripping the breaker, it's pretty clear (though I supppose it's not entirely certain) that you have a short. An ohmmeter is the way to find it.

The capacitor could be the place, and that would be good I guess because they are cheap comparitively. IIUC, new caps have two caps in one can. One could be shorted while the other is fine. You shouldn't measure for a short until you meausure voltage between the common and each of the other leads. If the cap is bad, one might have voltage and the other might not. The voltage might be enough to burn out part of your ohmmeter. If the cap is still good, both halves might be hot. If the cap is hot, holding a charge, and has stayed hot while it was raining, it's probably good. But if you want to check more, if it does have voltage, you could apply a screwdriver with an insulated handle to the two connectors and watch for a spark. Then do it again and watch for a second spark. That should discharge the cap. Then you can measure the ohms and they should be verrrry low as current flows from your meter into the cap. With a small cap, the ohms would start to increase as the cap filled, but I reallly don't know how long that would take with one of these. This is much easier to see with an analog meter, a meter with a needle. The needle goes all the way to the right, and slowly back to the left. But like I saw with these caps with high capacitance (and 25 microf is a lot) I don't know how long this takes. I'd say if at the start each part of the cap shows substantail voltage, the cap is good.

It's not likely the contactor is shorted, and if it is, you should see sparking damage. If you want to check one more time, you can be looking at it when the 220 breaker is turned on one more time, and you can watch the contactor. If it trips but you don't see sparks there, that's not the problem.

I don't know if the outside fan is 110 or 220. I guess if it doesn't turn when the inside fan is turning, it's 220. That motor is a lot cheaper than a compressor. With my ac, you can take off the case, take off the fan blade, take off the plate, I guess it is a rain shield, and look for spark damage, and have someone look at that at the smae time yuou turn on the breaker, and see if that sparks, although maybe it sparks underneath where you can't see it.

Oh yeah, you should also measure the resistance of the two wires to the fan, and the two wires to the compressor. The compressor uses a lot of current so the resistance might be low normally. (I think it would present as higher to the AC house current than it does to the DC current from the battery in your ohmmeter.) I don't know what would be correct. Zero is too low.

This was worth doing. Is this the same CB that keeps tripping and where you measured 200 amps. I don't think so, but you didn't draw a distinction.

Oh, don't complain about Oscar's jokes. It was funny and beggars can't be choosers. :)

[Ignoramus2645]

Yes, that's right. You got it 100%. Here's the schematic:

i

[Ignoramus2645]

It depends. If it is a cap, I can buy one tomorrow. If it is the motor shorted, I will have to hire a pro.

i

[Ignoramus2645]

The control voltage is 24VAC.

OK, thanks. I appreciate your tips, will try some of them for sure.

i

[mm]

Yeah I know, but I still think of it as 110 because that's what it is before it goes throught the transformer.

[Stormin Mormon]

Please trim excess text. We don't need a Christmas Tree at this time of year.

[Stormin Mormon]

Trim this tree.

[Danny G.]

It's probably 5k "before it goes throught the transformer" for your home service.

8)

[mm]

You're right! I should probably think of it that way.

Darn, now I'll be afraid even to plug in a lamp.

[Dido]

most likely you will need a new compressor from DIDO

[Richard J Kinch]

Where you at? 13 KVAC hereabouts.

[Ignoramus1064]

Yep, that is indeed the case. I will get a whole new system.

i

[Danny G.]

I was just teasing about the transformer thing. 8)

[Bruce L. Bergman]

All depends on where "here" is. they run local distribution to the poles behind your house in various areas at 2.4KV (rare anymore)

4.8KV, 9.6KV, 13KV, 15KV, 34.5KV...

And long distance can be all the way up to the 2-wire 1000KV DC Pacific Intertie - one line at +500KV DC, the other at -500KV DC to ground. Normally, DC isn't good for long distances, but boosted that high it works. And better yet, the transmission systems at either end don't have to be at the exact same frequency, because the converter stations sync up with the local AC frequency lock.

But back to the original subject - Igor, you can't get hurt with the

24V from the furnace to the contactor - there's a 40VA to 60VA transformer inside the furnace, and when the current goes up past what the transformer can supply the voltage drops off. (Till the fuse in the transformer pops, then you get nothing.)

There's a reason they call it "Class 2 Current Limited" wiring, and you don't need to worry about silly things like conduit and boxes.

Now the 240 VAC from the breaker, THAT can hurt ya.

-->--

[mm]

But now I'm sitting in the middle of the room, as far from the outlets as possible. I had to get an extension cable for my computer keyboard.

And there's that asbestos, too.

>