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OT: I Fixed It With Trash

Growing up having a country grocery store 60 miles from town we often couldn't get a professional anything out to fix stuff. On the rare occasions when we could the mileage charges and extra time cost double what it would cost in town. Usually more than that because they often didn't even have the parts.

I learned basic electrical and plumbing at an early age. More a common sense logic flow approach to problem solving.

My dad made friends with a guy who was in the refrigeration business who taught him the basics, and then he ordered a mail order refrigeration course. I read all the books and in my early teens started servicing our commercial refrigeration equipment. I am not and have never been a refrigeration technician. It was just another skill and set of knowledge I learned as a country shade tree mechanic. Like pulling an an engine or dropping a transmission. In modern days of course all the EPA regs make it "difficult to self service, but not impossible.

I have a friend who has a refrigeration license as part of his families corporate business and whenever I tackle a "regulated" part of a project I invite him over to supervise and buy him a nice lunch anywhere he likes afterwards. We technically obey the law, recover coolant (I have a recovery machine and so does he), and couple vacuum pumps and a recovery tank. When he loans me something like a CO2 tank I return it full, and when I came across an owner acetylene B bottle I gave it to him. We take care of each other. Even if we haven't spoken in months.

Five (+) years ago one of the two air conditioners on my house failed. The compressor locked up, and I called the local Tranedealer thinking I'd just pay the price and be done with it. The tech they sent out got it wrong. I knew he had it wrong, so I asked him what it would cost if he was wrong and I was right. The price he said off the cuff was more than a complete new heat pump and new air handler. I thanked him and said I'd let him know.

Of course I started doing some research, and my friend suggested trying a hard start kit. I tried the hard start kit, and it worked for about two days.

I was able to find sources for an exact OEM replacement compressor, but surprisingly expensive. Then I found a warehouse store in Michigan who was selling some on eBay. Including truck freight it was half the cost of other sources.

It took me about two weeks from failure to restoration during which I had curtained off that half of the house so the other AC didn't have to overwork. I did everything right. I set up a brick pad to setup an extra tall ladder to hang a come-a-long for the compressor swap. Proper recovery into a bottle marked with the words BURNOUT and the refrigerant type. Acid neutralizing flush. Nitrogen flush. (Cheaper than CO2 in the long run and more in a bottle). A little acid neutralizer in the new compressor oil just in case. Pulled a vacuum over night. Filled it up, and started it up. Just to be proactive I installed a new contactor and a new dual motor capacitor.

Until a couple days ago It ran just fine. It was tripping the compressor breaker, and it seemed on the surface of it that the compressor had burned out. I had other more important chores so I pulled the disconnect and left it until yesterday morning. I started pulling stuff off to get at things, turned the breaker on, and plugged the disconnect in with it hot so I could see the moment of failure. It sounded like the compressor was locked up, but the motor was trying, and then the breaker tripped. I did it a couple times before I realized the fan was struggling to start too. It would spin up, but slowly and didn't seem to reach full speed.

I was not hopeful for an easy solution, but I had a little hope at that moment. I snapped a picture of the wiring, pulled the wires off the cap and tried to read it with my old Ideal meter. It didn't make sense. It was like both internal caps had failed. I've never seen that before. Usually one side fails (often the fan motor) and the other side is still good. I wasn't sure I was reading it right or maybe that my meter was bad. Then I saw the old CAP laying in the dirt between the brick pad I'd made for a solid lifting base and the foundation of the house. For the heck of it I read the old CAP and it tested in spec on both sides. My meter was good and I was reading it right. I pulled the mounting strap, swapped the CAP for the "trash" one I had just picked out of the dirt, and the AC unit fired up and ran perfectly when I plugged the disconnect back in again.

It took me longer to put everything back together than it did to perform the actual repair.

I literally fixed the unit by picking a piece of trash out of the dirt and stuffing it in there.

Reply to
Bob La Londe
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I literally fixed the unit by picking a piece of trash out of the dirt and stuffing it in there.

--------------------------- Congrats, you beat the System.

When I worked in the automated test equipment industry I learned how to test components with a DC power supply. For caps I use a voltage and current adjustable supply to apply a few milliAmps with the voltage limit set to the cap rating. The voltage on a good electrolytic will rise steadily and hold after the current is disconnected, DVMs usually have a 10 MegOhm input resistance that will slowly discharge the cap. The cheap HF DVM is 1 Meg. A bad cap will stall at the voltage where its leakage increases. The formula C=IT/V gives the capacitance when you know the current and time to charge it. Degraded capacitors are pretty obvious when tested this way, plus reforming stored ones every few years seems to prolong their life.

This gives simpler methods that do the job but won't identify a marginal cap as clearly.

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Be careful to discharge the cap afterwards, and between testing the two polarities on AC motor caps.

The automated test equipment measured the component to determine if it was within spec or not. It appears the ones that were slightly below spec went to Radio Shack and more recently Amazon, at least that's what my testing showed. Analog Devices sent us op amps that tested well above spec to use in the production line testers we sold them.

Reply to
Jim Wilkins

The little Ideal meter was a gift from my dad when I started messing with 3 phase CNC stuff. He thought I might need to be able to read phase rotation. I have never used it for that. I am aware that running some types of pumps backwards could destroy them, but a spindle is faster and easier to check with the poor boy "run it and see" method.

This meter has a CAP test function and it seems to read okay.

Reply to
Bob La Londe

The little Ideal meter was a gift from my dad when I started messing with 3 phase CNC stuff. He thought I might need to be able to read phase rotation. I have never used it for that. I am aware that running some types of pumps backwards could destroy them, but a spindle is faster and easier to check with the poor boy "run it and see" method.

This meter has a CAP test function and it seems to read okay. Bob La Londe

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I looked up this Ideal meter to see how much voltage it applies to the cap, but it doesn't say.

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Hand-held, battery powered meters generally don't apply a high voltage to the Device Under Test, as it would be dangerous to the user. My high voltage leakage tester produces the voltage with a hand-cranked generator, which keeps both your hands occupied and off the test leads. Measuring the capacitance at low voltage won't detect faults like leakage at a higher voltage.

An expensive professional high voltage insulation tester:

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My cheaper one:
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By paralleling a DVM it will find capacitor (and motor) insulation breakdown voltage, though its low output current charges electrolytics very slowly. The built-in meter measures and displays the ratio of voltage to current which equals resistance, but not the voltage itself. That's regulated by a centrifugal slip clutch on the generator.

I was lucky to be out sick the day some recently graduated electrical engineers tested the phase rotation on a large power supply next to where I was working. I came back to a black stain on the floor and up the side of the machine I was building, and never saw them again. It seems they had been squatting beside the supply, touching the 480V cables to the input terminals, and one slipped and touched a large DC electrolytic.

Reply to
Jim Wilkins
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I managed to talk the company into getting a Sencore Z-Meter many years ago. Its high voltage was pretty basic, just some presets topping out at 600v. It could measure inductance too which was harder to check/measure than capacitance at the time. I found its series resistance measurement on high value capacitors to be the most helpful. Something I couldn't really measure with my basic BK Capacitance Meter...

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Reply to
Leon Fisk

I think that may be the newer model of the same meter I have.

I spent a couple winters running the hydraulic press in a cotton gin on the night shift. One day some equipment was down and the head ginner had me up on one the catwalks assisting. He had one of those little cheap analog meters we sold in my dad's hardware store and he was checking fuses with it. 440-480 volt motors (I think) on a machine called a moss. Basically a giant rotating bin dryer. He had just checked the the third fuse when I realized the disconnect was not turned off. Whew! We dodged a bullet there. If one of those fuses had been bad it would have been bad! Then without switching the meter I saw him start to put the leads from one fuse to the next. I didn't see him make contact because I was already facing the other way by then. The explosion was impressive, but the blue flash reflected off the far walls lit the gin up like daylight. I turned back to see if he was okay to see him standing there looking a bit sheepish holding a molten blob up by one of the leads, and he asked, "Do you think your dad will make good on this meter."

Reply to
Bob La Londe

...The explosion was impressive, but the blue flash reflected off the far walls lit the gin up like daylight. I turned back to see if he was okay to see him standing there looking a bit sheepish holding a molten blob up by one of the leads, and he asked, "Do you think your dad will make good on this meter."

Bob La Londe

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He was lucky. A tech working close to my bench hooked a scope probe to the gate of an SCR and the ground to the cathode, not considering that the SCR was on the hot side with optically isolated control. When he hit the breaker the probe cable exploded violently enough to send him to the ER, and I never saw him again to hear about it.

At the same job I happened to be looking at an aluminum-wired breaker panel about 20 feet away when the door blew off with a loud bang and a big red flash.

I was the battery tech for an electric car project with a 300V battery that required some internal testing to be done hot. I'm very happy to have no "interesting" stories to tell about it.

Reply to
Jim Wilkins

On 6/23/2023 12:30 PM, Bob La Londe wrote: [...]

Just to be proactive I installed a new contactor

I hope that you gave the cap supplier an earful!!

Reply to
Bob Engelhardt

On 6/23/2023 12:30 PM, Bob La Londe wrote: [...]

Just to be proactive I installed a new contactor

I hope that you gave the cap supplier an earful!!

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"The old ones with hazardous chemistry lasted forever, but newer ones don't last long. I usually wait a year after replacing one and then order another one to keep on hand."

The hazardous chemicals were preservatives that absorbed hydrogen and buffered the pH to slightly acidic.

Reply to
Jim Wilkins

I don't even remember where I bought it. Its been a few years.

Reply to
Bob La Londe

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