That’s called a digital compressor. The plug you found hanging loads the compressor when energized. Which is kinda weird. Semi-hermetics energize to unload. As far as Carrier goes the first 2 digits in the model number indicate gas or electric heat. 48 is gas and 50 is electric heat. Stay safe brother.

You have my sympathy. I've also had to study some types of diagrams for a while that were confusing and frustrating to me at first.. The longer I would study them the more they would make sense until I finally understood. I would beat up on myself because I felt I should have been able to get through that process more quickly than I did.

Hey Bill - new to your channel . Good video. The impedance of the unloader will depend on the series -the ZPS -K4 compressors have a resistance of 330ohm . The ZPS-K5 compressor has a resistance of 1640 ( source A )or 350 ohm source B

Please make a part 2, this is interesting ive never seen one either, seems like you got it, unfortunately for the customer they've probably spent a lot of $ on that unit

Ive never seen that plug before. My first thought was crankcase heater, but yeah.. thats how the trade is, theres sooo many things we can learn.

Carrier tonnage is in the numbers after the "48TC...", so in this case the "08" that follows. I believe that's a 7½ ton unit you've got there. About 8 years ago I ran into a similar problem that really stumped me. We had a Carrier unit with an intermittent low voltage short. Cooling would run in test mode, but after a few minutes it would cut out. Couldn't find any immediate clues.The compressor with 2 thin blue wires coming off the back which I had never seen before. What I thought was some kind of thermal overload was actually a stage 2 solenoid. Apparently it had a short, and we had to replace the compressor. Never saw another one since.

I always wondered what those wires were for haha. Luckily I'll be a step ahead if I run into this same issue in the future. Keep up the good content brother.

If you look at the whole data tag you can easily tell it’s not a 4 ton, 5 ton, or 6 ton unit. Right above the two bar codes and below the Intertek logo it says “Cooling Capacity 88000”. So that makes it a 7.5 ton unit. Pause the video at 0:27 and you can plainly see it.

Your second stage for cool sends 24 dc to the plug and that energizes the second stage cooling.

Wonder if the high supply temperature you were seeing was because it was in reheat mode trying to dehumidify. That would have greatly reduced the cooling capacity as it was already running at half capacity. Potentially pulling the reheat call would allow it to maintain temperature a little better, until the compressor is swapped.

We never stop learning, thanks for this very interesting video.

48 means gas pack. The capacity is in tens of thousand BTU so a 48HCD06 would = 60,000 btu which = 5 tons. *The plug on the back of the compressor is the LOADED plug for the 2 stage scroll* So with that unplugged you were down to 70% total rated capa ity. With the supply on high speed with Y2 call you'd have horrible split temp

Misspoke I am sure, but it was a Y2 call and not a W2 call. The dotted line did not go to reheat, it went up to 8 before it "landed" at reheat. A txv takes the place of the Acutrol metering devices, so there should NOT be anything else to meter the refrigerant past the txv. I am not familiar with that unit specifically, but I do not recall ever seeing a LL solenoid in an RTU. The look of that install of the LL solenoid screams retrofit, kind of like the heat block on the txv.

Nice work Bill.

I ran into a fun one this week. Had a liebert unit that wouldn't cool and the hot gas bypass was staying engaged and the liquid line solenoid valve wasnt opening. It had me confused for a bit. The HGB staying open because the LLSV wasn't opening made sense to me. After some thinking and digging and tracing I found that the solenoid coils had been switched by someone for whatever reason. I was dumbfounded by that. The most confusing part was I was getting voltage to the LLSV coil the whole time but that valve wasn't opening.

The resistance of the loader would not be that unusual if the voltage that feeds it is AC due to inductive reactance. I wasn't really sure if you were saying there were diodes in the circuit and I'm not able to read the schematic on the display to tell. If there is one or more diodes in that circuite then it's going to be a DC voltage. With a DC voltage supply 0.4 ohms is pretty low.

70 degrees is normal supply air if the unit is in de-humidification mode. That solenoid allows hot gas to go to the reheat coil. There are also two other solenoids in the blower compartment to control the refrigrant flow through the reheat coil to hold the return and supply tempature the same. Essentially loading the space with the reheat coil so you can keep running air through the cooling coil for hours on end. A digital compressor! The unloader allows the scroll plates to separate in a 15 second interval, so 7 seconds off, 7 seconds on would be 50% duty cycle. 1) This is better than an inverter driven compressor because the refrigerant velocity doesn't change in the on cycle. VFD running a compressor slower speeds causes the suction line to be oversized and that can cause oil return problems. 2) There's no expensive VFD in the mix. Sometimes you can hear the compressor making a clicking and tone change as the compressor engages and disengages, motor speed doesn't change. They sound broken when working properly.

I like that no blinking

Did you ohm out the unloaded terminals in the compressor? Should have had like 10-14 ohms for that coil. If low (5) ohms the coil is internally shorted. ( comp change out) OR if the terminals are grounded too. Point is, now your SURE that is the issue.

What did you find on the second RTU? Will that be a third video?

nice job

Copeland used 2 different manufactures for the compressor solenoid unloader and each has a different ohm readings.

Did you check the evap. coils entering air temperature when you recorded the S/A leaving air temp @ 70 degrees F.

The Copeland Mobile and AE Bulletins apps will tell you everything you could ever want to know about Copeland compressors.

Isn't that a solenoid for mechanical 1-2 stage modulation?

Great video Bill

Curious, why would W2 kick on? Is that the signal for the unloaded?

I've never seen that either. I wonder if more information available on the Emerson site for the compressor? just a thought.

the question is,what caused the unloader to fry ?

Turns from a 2 ton to a 4 ton with only 1 compressor...I thought it was a humidification thing but that opens the unloader???? Wow that's a different way to do it...only carrier

If only the unloader, or more of a half-unloader would have failed to 2stage eg power supplied to it = single stage, you could have worked around the fault by cycling the compressor instead

No that is not a digital. That is a 2-stage compressor receives an AC signal from the board, and gets converted to DC buy a rectifier within that plug. Make sure that you have 24-volt AC off of the board. Then check that cell annoyed on the compressor itself. If the solenoid is good and voltage from the board is right, replace that plug. If the solenoid does not check out, replace the compressor.

2:45 that’s the connection plug to the compressor know wonder why the unit wasn’t working 🎉

Carrier has a weird model number nomenclature. The numbers after the letter string are the tonnage, and it's always one size less than the number. Yours said 8 so it's 7.5 ton I believe. Crazy carrier always gotta be different. 😂

Nice job, Bill!

It has a humidimizer in it.

I’m somewhat sure that solenoid is a for the dehumidification reheatcoil.

“Makes my brain hurt” ha! SIR what it all boils down to is. . Well . . Fucken things sucks 😊 stay safe out their!

Never see a extra plug like that.

🤘👍

0.5 ohms = short for sure at 24 volts

Two stage compressor.

you really need to go back to working at Mcdonald's, at best a helper.