Air Compressor puzzle

[grsthegreat]

Just a note. Some smaller compressors cant start if too cold. They run slowly and sound lugged for a few seconds then pop little push fuse. Ive seen many units fail in cold winter that run fine in summer

 

[arrow]

Just a note. Some smaller compressors cant start if too cold. They run slowly and sound lugged for a few seconds then pop little push fuse. Ive seen many units fail in cold winter that run fine in summer

I did think of that. The day it failed was one of those freak 65* days we got in the Northeast a few weeks ago. Most of that entire week was above 50*. I didn't see a "fuse" anywhere but if there was one and it did pop, I'd get no start whatsoever.
At any rate, I ordered up the $30 start capacitor. I also have an unopened Kobalt 26 gallon ($269) waiting in the garage. Specs do not seem to hold a candle to the DeVilbiss made Craftsman. If the starter cap works, the Kobalt is going back.

 

[Gary Fowler]

I hope you aren't using a 25or 50' extension cord. That will severely impact the amperage and voltage that is getting to the motor. Even with a heavy SO extension cord of 50' in length, my compressor wont start with it unless the tank is completely bled down and even then it may hum a bit before starting. Always plug straight into the wall receptacle and then use hose extensions to get to distant spots.

 

[arrow]

I hope you aren't using a 25or 50' extension cord. That will severely impact the amperage and voltage that is getting to the motor. Even with a heavy SO extension cord of 50' in length, my compressor wont start with it unless the tank is completely bled down and even then it may hum a bit before starting. Always plug straight into the wall receptacle and then use hose extensions to get to distant spots.

Never used an extension.

 

[arrow]

So I order a new start cap which is returnable if I do not open the package. Before I do so, I think to put a meter onto the present start cap so I broke off the resistor and proceeded to test the rather good looking cap (no bulges and totally intact including the relief). Needle pegs all the way and adroitly returns as it is supposed to. Something is telling me it is not the start cap. The run cap also tested successfully in the same way.
As a result, there could only be two things left. Bad windings (of which I would not replace the motor) or bad starter switch which I would also not replace due to the $132 cost. Unless I'm missing something, it appears a new compressor is in my future.

Anyone know what this little disc on the top part of the motor labeled "CRJ500" does?

 

[flyerdan]

Looks like a bimetalallic auto reset circuit breaker. If overloaded and things get hot, it will 'pop' to keep things from burning down. When it cools enough, there will be a click and it passes power again. Like the ones in coffee makers that click on and off to regulate the heat plate temp.

 

[wawoodwa]

Can you measure the windings? Make sure you don't have a short/open?

 

[wawoodwa]

I'm still pulling towards a start cap. But it isn't my money. If the windings are good, I'd go with a start cap.

From the web, "where everything is true:"

Eyeballing Doesn’t Cut It

In addition to airflow problems, one of the biggest killers of a compressor is a weak run capacitor. Many technicians think that if a run capacitor is weak it will either leak its internal fluid or the casing will be swollen. So if these two conditions aren’t visibly noticed the capacitor is assumed to be okay. This simply isn’t the case, as there are millions of weak capacitors in operation this very day because they aren’t being tested, just visually verified. To make matters worse, the visual verification method is even listed in some quality maintenance checklist, so the assumptions continue. In order to truly verify a capacitor is firing within its specified tolerance range it has to be tested.



Some technicians including myself were taught to look at the swing of a needle on an analog multimeter to determine if a capacitor was firing properly. Unfortunately this doesn’t tell you how strong the capacitor is it only tells you that it’s storing and releasing a charge.

It is referencing a run cap, but you already replaced that. The only other thing that typically fails is the start cap.

 

[Redneck in training]

I was told by a Sears tech that this motor does not have a separate capacitor for start/run functions. The switch turns the thing on ok but it just isn't getting to speed. What's this thing I found in there?

That is start capacitor. About $30-35 for new. Google Mallory 136-163 MFD. You can substitute another brand as long as the capacity is close to 136 - 163 microfarad, voltage is 220 or higher and it fits inside. Airconditioning and refrigeration service should have some in stock. They should also be able to test yours if it is bad. Many digital multimeters have capcitor testing function. AideTek DM47 LCR meter multimeter tester capacitance Inductance Resistance self-discharge compared with FLUKE - - Amazon.com
or this one
Amazon.com: BSIDE ACM3 Auto Range Digital Clamp Meter 4 AC DC Current Hz Tester by BSIDE: Home Improvement

 

[MossRoad]

That capacitor is fairly cheap, as low as $12 with quick google search of "Mallory 625622-1". I see you have one on order. Cheap experiment. If you end up getting a new compressor, keep the old tank as an expansion tank. Sometimes handy to have more capacity.

mallory 625622-1 - Google Search