Startup problem - help!

[emsloan]

I have a 4-ton unit for 2K sqft MH. Not sure of the brand, info has faded out. It is pretty old 12+ years. For several months the compressor has had a startup issue - sometimes taking several tries to start and then with a groan. Occasionally it trips the 40A breaker. Once going it cools great. Recently it stopped working, no hum or anything. I pulled off the side panel and took out the large silver 3 terminal cap. Took it to the elec supply place and they tested it and said it was good. When I put it back in the unit I noticed that the relay device for the main power (contactor?) had come apart on top. It costs about 30$, its part number references to Intertherm, Nordyne, etc units. I hate to spend the money for it if its not going to fix the start issue. Could a dying contactor cause the issues above? Any way I can check to see if the compressor is seized up or going out? Thanks!

[paul52446m]

I have a 4-ton unit for 2K sqft MH. Not sure of the brand, info has faded out. It is pretty old 12+ years. For several months the compressor has had a startup issue - sometimes taking several tries to start and then with a groan. Occasionally it trips the 40A breaker. Once going it cools great. Recently it stopped working, no hum or anything. I pulled off the side panel and took out the large silver 3 terminal cap. Took it to the elec supply place and they tested it and said it was good. When I put it back in the unit I noticed that the relay device for the main power (contactor?) had come apart on top. It costs about 30$, its part number references to Intertherm, Nordyne, etc units. I hate to spend the money for it if its not going to fix the start issue. Could a dying contactor cause the issues above? Any way I can check to see if the compressor is seized up or going out? Thanks!

Hi Paul here, Yes the contactor points getting bad can make it over amp. The more it runs that way, the more the points get burned. Check the wires going to and leaving the contactor to see if they are burned also. If you know how to jump all the wires across the contactor and then repower it with the blower inside running, that would tell you if the compressor will run. I would not recommend a home owner to do this unless they know what they are doing. Later paul

[emsloan]

Thanks. The top part of the contactor is gone - there are 2 connector brass pieces about 3" long left with a yellow wire connected to the end of each one. I don't see any points. Do the bottom wires connect to the top wires when actuated by the t-stat transformer? I drew a pic showing how the wires connect to the contactor before I removed them, but not sure which connect to which when turned on - about 5 black ones not including the t-stat wires which I won't need.

[emsloan]

OK, I see the points, a pair of contacts that are connected. Using my ohmeter it looks like, pushing down on the points, that the bottom black wires connect to the top. I'm not sure about the yellow wires that are connected to each end of the dangling terminals.

[emsloan]

another correction

The danglings strips is just one strip. Looks like it mounted on the left side of the contactor. The strip top is connected to 2 yellow wires and the bottom goes to the power wire from the fuse box. Its not a switched connection. So I can just jumper the black wires across the points?

[paul52446m]

OK, I see the points, a pair of contacts that are connected. Using my ohmeter it looks like, pushing down on the points, that the bottom black wires connect to the top. I'm not sure about the yellow wires that are connected to each end of the dangling terminals.

Ok this depends on what contactor you have. Most of the ones used in air con.
only have one set of points, because they only break one side of the 220 power. So you are right on the wires being broke through the points. The other wires are connected to that terminal bar that you are seeing. Like i said before,
those wires that were tied to this contactor might be burned under the outer coating, so check for that. You might have to cut off a few inches of wire so you have good wire or you will be over amping again. Later Paul

[HayZee518]

fan contactor

here's three pictures of a single pole fan relay. ebay has them as does an intertherm site

[emsloan]

Its the one in the first pic with the plastic top gone. L1 goes to the white power wire and is connected to T1 with the yellow wires. L2 goes to the black power wire and connects thru the points to a couple other black wires at T2.

[HayZee518]

then by means purchase a new one. the top piece is part of what is called an ARC SHIELD. when the contacts open the shield helps to contain the arc within the contactor.

[paul52446m]

Its the one in the first pic with the plastic top gone. L1 goes to the white power wire and is connected to T1 with the yellow wires. L2 goes to the black power wire and connects thru the points to a couple other black wires at T2.

Make sure if you buy a new contactor that you get one that is rated for
40 amps. They make them for different amp rating. If you buy to low of amp
rating it will over amp and it won't last long. later paul

[emsloan]

Well, I hooked the contactor back up and jumpered the points. The fan in the top of the outside unit came on and otherwise I hear about a 1 second hum followed by about a minute until another 1 sec hum and so on - compressor trying to start. Before, this same scenario until it started, but the fan was not coming on till it started. Hope I got it wired right. Is there supposed to be another cap somewhere besides the 3 terminal can? Don't see one.

[paul52446m]

Well, I hooked the contactor back up and jumpered the points. The fan in the top of the outside unit came on and otherwise I hear about a 1 second hum followed by about a minute until another 1 sec hum and so on - compressor trying to start. Before, this same scenario until it started, but the fan was not coming on till it started. Hope I got it wired right. Is there supposed to be another cap somewhere besides the 3 terminal can? Don't see one.

If you had the wires right and the compressor would not start, then you need to have a air con. tech check it out. A good service man would have a tester that he can put on it to dial up a stronger start cap. and kick the power back and forth to try to run the compressor both ways to break it lose and see what it does. all the time keeping a check on the amps. But this tester is costly to buy
so not every tech has one. Later Paul

[emsloan]

Well, it started after throwing the breaker several times. Cooling good. Does this thing have a compressor and a compressor motor? If so, could it just be the motor and not the compressor itself? Do you think the can cap is both a start and a run cap?

[emsloan]

If I have to replace the compressor/motor, I am going to look on craigslist for a used unit. My MH is a '97 model. The outside unit has the compressor, exhaust fan and a radiator(condenser?). Is this what is called a split system? What is the highest SEER unit that will work with it?

[HayZee518]

I think you are going about this in the wrong direction. You find a contactor that's blown apart and automatically you think the compressor is shot. Please go about this in a systematic direction. First, annotate which relay is the fan relay or contactor. Next, determine which contactor is for the compressor. The inside fan has its own contactor. So, that's three contactors you have to look for. The control circuit is all low voltage 24 volt. The cap you say has three terminals. ok. it is a dual capacitor - one side for start, one side for run. Don't go jumpering around in the circuit until you know what you are doing. You are gonna blow up something.