Just for the hell of it can you take an ohmmeter measurement from any of the three terminals to the case? It should show open (very high resistance). If it measures any resistance, the compressor is bad.
I hadn't thought of that. I did avoid touching the chassis. :)
Thanks for explaining that the start current is much less than the run current, so the motor "sounds" wouldn't be easily discerned.
I don't know how to test for a plugged freon line either. :(
Thanks for that idea. I just reversed the START and RUN terminals, and there was no difference. It hummed but didn't kick on.
One problem is that I can't tell what's going on from the sound, but when I hooked all the old parts back, it kicked off again as it did when I started this thread.
Sigh.
Ah, resistance. Why didn't I think of that. I'll make a test jig out of the existing wires, and put a 5K ohm resistor on it. Thanks for that idea.
The main problem I have is that I don't know what a good compressor humming sounds like, compared to a bad compressor humming.
Is it safe to leave the test jig in place for an hour or three to see if the lines get cold?
Heh heh... You should have heard the wife scream when "I" got zapped by the
12uF capacitor!
Thanks for that advice, as I'm at a loss as to how to know the humming sounds of a good versus bad compressor.
I did check the resistance when I was trying to figure the pinout of the compressor three pins, and all are insulated.
But thank you for that idea as I had not mentioned that test.
If the compressor is running, the discharge line (the smaller copper tube) will get warm (hot).
That's a good point! Maybe it IS running with test jig. Do you have an AC ammeter? If so, check if the run current drops after a second or two with the test jig. If so, it's running. But if it stays high, it's not.
If it isn't running, the excess current from it being in the start mode continuously will overheat the compressor. That's what the overload device was protecting against. You might be thinking "So what?" & I see that point, but I'm not going to say that it would be safe.
Bob
Which line in this picture is that "discharge line" that will get hot?
How long will it take to get hot?
I have a 10Amp Fluke 77 but I lent it to an ex brother in law, and it has never returned. So, currently I'm stuck with a radio shack dial ammeter, but it does have an inductive clip that I can clip on.
Looking at the manual it has 3A, 15A, and 30A AC current ranges.
I don't want to burn down the house for a frig!
Actually, I just realized I could leave the START wire off, right?
So the question is whether it's dangerous or not to just run with the two wires connected to the compressor for a few hours, RUN and COMMON?
Well, you need the Start wire for a few seconds, to get it started. Then the Start wire should NOT be connected.
But that doesn't change whether the compressor will overheat. Which it will if it hasn't actually started. With the overload protector in there, it only took, what, 20 seconds to trip? The engineer who designed it thought that 20 seconds was the longest that it should "run" if it hadn't started.
Bob
Excuse the previous null post - brain fart.
That's good - I would use the 15A range, 3A isn't going to be enough.
The small line on the far right is the compressor high side (output). The bent tube in the center is the process tube where the system is pulled to vacuum then charged with refrigerant. The tube on the left is the suction line and pulls evaporated cold gas from the cold coils inside the refrigerator.
Do a google search on refrigeration cycle for more details.
It should begin to heat up quickly (minutes or so) if the compressor is running.
This may help you if you have a good meter that will read low ohms.
One other thing to search on is CSIR compressor. That stands for Capacitor Start - Induction Run motor. Since you unit seems to only have the one capacitor, it is likely a CSIR compressor. If you can pop open the start relay and see if there really is a relay, it will be a current relay that on start up the high current pulls in the relay and connects the line high to the start winding. Once the compressor is running, the relay drops out and disconnects the capacitor.
You can do as the one poster suggest and make up jumpers and see if you can get the compressor to start. Identify the three terminals (C-S-R for Common, Start, and Run)
Think through the problem and you should be able to make some progress.
Thank you for that reference which said: a. The highest reading will be the ?Start? winding b. The next highest reading will be the ?Run? winding c. The lowest reading will be the ?Common? winding
Unfortunately, I lent my Fluke DMM to my ex brother in law, and he hasn't returned it yet - but I did check with the emergency Radio Shack dial meter, and I think I've properly identified the COMMON, START, and RUN terminals on the compressor.
I zeroed the Radio Shack meter, and put the ohms on the lowest setting (RX100), and tested.
Also, I checked the resistance to ground (i.e., to the copper pipes). First I checked that the copper pipe was grounded, and they were. Then I checked each terminal on the compressor to the pipe and they were all infinite.
So, *electrically*, the compressor checks out perfectly (within the abilities of my instruments).
There is the mechanical part though ... still to test.
Hi Bob, Thanks for sticking with me in my hour of need!
I think the problem is mechanical, so I'd first like to clarify the inlet and outlet.
Is the inlet on the right and the outlet on the left in this picture?
I am not sure if I interpret Locked Rotor Amperage (LRA) specs correctly (from googling), but this sticker on the R134a compressor shows a LRA of
17.6 amps, so I think the inrush current is 17.6 amps, so that would take the 30A scale, at least initially.I tried the test with the capacitor, and without the capacitor (using a screwdriver to momentarily short the RUN and START terminals).
Then, as you suggested, I started on the 30A scale:
On the 30A scale, the inductive current is 12A:
On the 15A scale of the meter, the meter is pegged:
I also doublechecked the resistance, which seems to show good numbers: A. COMMON to START = about 5 ohms (hard to read the Rx100 scale) B. COMMON to RUN = slightly less than 5 ohms C. START to RUN = slightly less than 10 ohms
Given all that, I tentatively assume that the motor is working fine electrically; but that mechanically, it seems to be locked up.
However, I would have expected 17.6 Amps if the motor were locked up, so, I'm curious why I get 12 Amps instead - but maybe that's because it never started?
Thanks for the information as to what the three tubes are.
How is the annotation on this photo?
The LRA is 17.6 amps and with just two leads on the RUN and COMMON, it's pulling 12 Amps.
I think I have to figure out whether there is a "restriction" in the flow of the R134a fluid/gas.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.