Proper ohm ratings between condensor compressor terminals?

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Proper ohm ratings between condensor compressor terminals?

Postby bmpero » Sun Sep 18, 2011 1:40 pm

5 ton,14 seer,Amana, Just turned 11 yrs old, Air handler is 9 yrs old.
The original problem was that when thermostat kicked on, the condenser unit would occasionally start up and run for no more than 5-10 seconds and then quit ( the handler would continue to run though). Then after the expected 3 minute 'delay on break' time, it would try to start again and it sometimes it would repeat this and sometimes it might start up ok. For those 5 – 10 seconds there were no unusual sounds or anything, it would start up normally.. the condenser fan was spinning etc. IF the condenser got past that 5 or 10 second period, then the AC would blow cold and run fine and cool the house.

..Well, I had an HVAC guy com come look at it and he said the pressures were all reading fine so he replaced the dual cap and contactor, but due to the intermittent nature of the problem, I didn’t find out until the next day that the same problem still existed.
j..Due to the failed efforts of the previous guy, I had a new company come out and this one suspected a faulty ‘delay on break’ simply based on his experience even though no tests showed any problem with it , so he ‘disconnected it’ by pulling one of the three wires off the delay and connected it I THINK to the contactor. He couldn’t reproduce the problem at that moment due to the intermittent nature of the problem, so I didn’t find out until the next day that the condenser sounded like it was having a heart attack at start up, very rapidly starting and stopping, etc so I shut it down. The next tech came out and found the unit sparking BADLY from the contactor (note the contactor is only a month old). But he replaced the contactor anyway just in case.. So I’m thinking the previous guy messed up the wires when he disconnected the delay.
..Now I decided to have a yet a different opinion from another company because so far there has been more part replacement than actual testing occuring. After I explained the whole story, he said the pressures were fine too, but he took multimeter readings from the compressor and says its bad and that I’ll need a whole new system. However, he didn’t disconnect the wires from the compressor first when connecting the multimeter (which I would think you should do when checking Ohms but I’m not sure), and seemed to quickly remove the multimeter the moment I approached which made me very suspicious. He didn’t check anything but the pressures and the compressor with the multimeter.
At this point I don’t know who to trust, and now I don’t dare run the unit. I’m not an electric expect, but am knowledgable enough to trace wiring, check/connect/disconnect what I am told electrically speaking, can follow a schematic, and have a multimeter. I have dumped over $500 into these guys so far and simply cannot afford $4,000+ this year on a new system, or even another tech visit at this point. I would think I should reasonably get another 5 years from this system, everything physically looks to be in very good shaped with very little rust or corrosion on anything.
1) There are three terminals on the compressor unit and I would like to know what the readings should be across them to see if the compressor actually is bad. I disconnected the wires from the compressor and checked ohms directly across each of the terminals and received readings of 1.1, 1.0 and 1.5, and I don’t receiving any readings to ground. Do those numbers sound right? I have found conflicting information on the web that basically the numbers should be the same.
2) To make sure the tech didn’t screw up the ‘delay on break’ wires…Where should each of the three 'delay on break' wires be connected to?

Please help. Thank you very much, Brandon
bmpero
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- Proper ohm ratings between condensor compressor terminal

Postby Freon » Sun Sep 18, 2011 2:00 pm

I do not have those impedence values and I sympathize with the "throw parts at the problem 'till fixed" approach you have had to endure. I would double check the replacement capacitor and make sure it's what is called for by the schematic. I would have a tech measure the current draw by the compressor at startup. I feel that's a far more meaningful indicator of what may be the problem. Since you say it does run after a few false starts, it seems the compressor is fine. I would suggest, based on age and symptoms, you may only need a hard start kit.
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- Proper ohm ratings between condensor compressor terminal

Postby bmpero » Sun Sep 18, 2011 3:00 pm

Thanks for the reply. Unfortunately it will not run properly any longer after a false start, as the sparking issue is larger problem that is not allowing the system to run ( which I seems like it was added to the original problem by one of these inexperienced techs.) It actually does have a hard start kit on it already though).
..I had double checked the cap they put in already, and both sides of the cap match what it says on the side of the compressor, except that it is a 440 rather than a 370 (which several different people I have talked to says is very common and acceptable to do).
..I'm wanting to double check the wiring from the delay and contactor to make sure they didn't screw that up somehow, causing the sparking, then I would be able to try and troubleshoot the original problem, so I need a some guidance there. I really don't believe the compressor is bad like this last guy suggested, as we were gettting cold air just fine if it would get back those first few seconds at startup..and at worst if it is bad, it has probably been killed but the subsequent sparking issue that has been introduced after the fact.
.. If/when I have a tech out again, I'll definitely make sure they check the current draw if they haven't already, but I'm trying to eliminate every other possible issue before having another tech out again that doesn't seem to know much more than me unfortunately..
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- Proper ohm ratings between condensor compressor terminal

Postby heatseeker » Mon Sep 19, 2011 10:02 am

it would sound S Though you have a tight compressor. In other words the moving parts do not have enough clearance when cold. A potential relay with a start capacitor would probably fix the problem. On the other hand the ohms don't sound right either. That could be a misreading though and its to hard to tell from here. on a single phase compressor start to common is highest ohms usually 2.5 run to common lowest ohms 1.0 and start to run is whats left over between them which would be 1.5n ohms. If it is different windings going or are bad.
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- Proper ohm ratings between condensor compressor terminal

Postby bmpero » Tue Sep 20, 2011 9:05 pm

Thought you all might want to know that it turns out apparently my one of my pressure switches is bad. He bypassed them and its been running fine for an hour now.
Note that after several different AC techs, it took a personal friend of a friend to finally find this out that didnt have a financial motivation. Wthout telling him anything about what had been done thus far it took him less then 10 minutes to find the problem. The compressor is NOT bad like the previous guy told me so that he could get me to buy a new system, and note this was supposedly a 'senior' from the largest HVAC company in my county. I got one of the techs to admit that their company will even hire people with ZERO training or experience, and just give them a few one on one lessons!

I am baffled how every tech that came out had no idea how to trouble shoot(and remember I tried several different companies) and just wanted to get new parts into it as fast as they could so they could give me a bill. I mean no offense to you honest HVAC techs, I know you are out there, but be very skeptical of ANYONE until you get a second, third, fourth and fifth opinion when it comes to HVAC.
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- Proper ohm ratings between condensor compressor terminal

Postby Beach » Wed Sep 21, 2011 11:20 pm

the readings you got is fine ...

compressor has three terminals
C - common
S - start
R - run

the start windings are tighter so to have more torque therefore higher resistance
common should be the lowest
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