'99 Pathfinder, Replaced AC System, Comp. Clutch Won't Engage

[knotworking]

Hi,

I've spent all today troubleshooting this AC problem. Yesterday I replaced the entire AC system on my '99 Pathfinder; compressor, radiator, evaporator, condenser, and receiver/dryer, AC lines are the only things I didn't replace (but I did evacuate them). Pulled a -30psi vacuum that held for over an hour, then evacuated the system for nearly 2 hours. My sticker called for 6.8 ounces of PAG, my compressor came with 6.1, I drained 2.5 ounces from it and distributed it (and the additional .7 ounces) to the new components and lines.

This morning I went to fill it up and the clutch wouldn't engage. I assumed this was because there was no refrigerant in the system, bypassed the relay and the clutch engaged, allowing me to add refrigerant. I filled the system up with 22 ounces of R134a, as the sticker recommended. Beautiful, cold air was blowing into the cabin, I was so happy. Unfortunately, when I removed the relay bypass and put the fuse back, the clutch again refused to engage. I swapped a confirmed working relay with the existing one, didn't make a difference.

Static pressure in the system measured ~100 degrees for both the Hi & Lo (it was around 88 degrees, at the time). When I bypassed the relay again, my Lo dropped to 45psi but my Hi only rose to 150psi. From what I've read, my Lo is in range, but my Hi is too low. Since my static measurement matched ambient temp, pretty sure I have enough coolant.

I'm stumped, hoping someone with greater knowledge could give me some things to test/try. I'm in Florida and it's at least another 3 months of unbearable heat....I'm feeling desperate/despondent.

[JohnHere]

It sounds like it could be low on refrigerant. How did you go about charging it? And did you replace the TXV? Also, don't bypass any fail-safes. There's a reason the compressor doesn't run.

[knotworking]

Thanks for the quick response John!
To refill after evacuating, I attached the refrigerant to the low side blue hose and opened it up with the clutch engaged. The sticker said it takes 1.34lbs +- .11lbs, so I planned to add 22oz. The cans I am using (https://www.amazon.com/Chemours-Refrige ... B088HGRJ3Z) are labeled Net Wt. 12oz, but there's no gas weight. I assumed that meant they held 12oz, but now I'm thinking 12oz was possibly the total weight. The empty can weighs 3.3oz. Wish I had a full bottle around to weight it.

The Pathfinder doesn't have a TXV, it's a block type with solenoid; I did replace that.

[tbirdtbird]

Since you are giving us both hi and lo pressures, it would seem that you have a manifold gauge set, have to wonder why you are not using the center yellow service hose, that way you can monitor both pressures as you charge. The cans have about 12 oz of 134, but you will never get it all out, more like 11.0-11.5 oz

Those cans you show are the so-called self-sealing type which are a pain to use. What we do in this shop is use a side tapper on those nasty cans, when we are forced to. Usually use 30 pounders, tho

[JohnHere]

To refill after evacuating, I attached the refrigerant to the low side blue hose and opened it up with the clutch engaged. The sticker said it takes 1.34lbs +- .11lbs, so I planned to add 22oz. The cans I am using (https://www.amazon.com/Chemours-Refrige ... B088HGRJ3Z) are labeled Net Wt. 12oz, but there's no gas weight. I assumed that meant they held 12oz, but now I'm thinking 12oz was possibly the total weight. The empty can weighs 3.3oz. Wish I had a full bottle around to weight it.

Using the blue hose has already been questioned. I wondered about that, too.

The newer self-sealing cans, by themselves, weigh slightly more than the old style cans, so you get a little less refrigerant nowadays. The best way to know for sure how much refrigerant you put into a system is to use a refrigerant scale, which takes into account the weight of the can itself and then counts down in reverse the number of ounces (or grams) of refrigerant you put in. A postal scale will do in a pinch.

22 ounces isn't very much, so just a few ounces off can affect system performance. Going by your calculations, you might have installed only about 8 ounces per can, or 16 ounces total. You can see that your charge amount could possibly be quite a bit short—enough short of a full charge to prevent the compressor from running.

A second option is to take it to a shop having an RRR machine (Recover, Recycle, Recharge) to have them install an exact charge.

[knotworking]

My apologies, I did use the yellow hose for the Freon (been a long day), and just opened the Lo/blue to fill. I'm thinking I should just put the rest of the second can in. Full @ 1.45lbs would be 23.2oz, so it sounds like I won't be overfilling. Definitely agree on the PITA that is self-sealing cans; I had to continually open/close the tap and feel the can for the temp drop to know it was flowing (the little window above the yellow hose is helpful, but hard to see in direct light without the neon leak additive).

Is there a way to figure out about how many ounces I have in the system? Is there a way too tell if I'm over-charged?

Thank you both for your time & knowledge

[JohnHere]

My apologies, I did use the yellow hose for the Freon (been a long day), and just opened the Lo/blue to fill.

Okay...good

I'm thinking I should just put the rest of the second can in. Full @ 1.45lbs would be 23.2oz, so it sounds like I won't be overfilling.

The specs I have say 23 ounces of R-134a. If you go with that amount, you'll be close to the maximum charge shown on the under-hood decal, which takes precedence, especially if you don't pull-in the refrigerant remaining in the Manifold Gauge Set hoses.

Is there a way to figure out about how many ounces I have in the system? Is there a way too tell if I'm over-charged?

Unfortunately, no to both questions. The pressures can give an inkling. But the only way to tell definitively is to recover the charge, evacuate the system again, and weigh-in the precise amount. Contrary to what we often hear on the Internet, you can't just top-up the refrigerant.

[knotworking]

Getting ready to head out and fill now. There is one other lingering question that's been worrying me. As I stated in the original post, the compressor I have (SPAM LINK) came with 6.1oz of PAG; since my system calls for 6.8oz of PAG and I'm installing all new components, I drained 2.5oz out (I couldn't get anymore to come out). What's worrying me is where I drained the oil from.

The screw I removed and hole I drained the oil from is in the picture below. After I drained, I noticed there is also a drain screw at the rear of the housing at the bottom. There aren't two separate/exclusive chambers in a/the compressor for oil, are there? I'm worried I drained the oil out of the chamber and it won't be replaced by the oil in the system and the pistons, etc., might be running dry. The oil is shared by the whole system, right??

[JohnHere]

Sometimes, what the manufacturer says about how much oil is installed in a new compressor turns out not to be valid. That's why the recommendation is to drain a new compressor of whatever oil might be in it and refill with the correct amount and type.

In addition to what came out of the drain plug, did you also try draining from the HP and LP ports while rotating the main-shaft by hand? Those ports normally are sealed from the factory with some type of plugs or bolt-on plates. You would need to remove those and then try draining from the ports. You might or might not get out any more oil.

The drain screw at the bottom rear of the compressor most likely is a HPRV (High Pressure Relief Valve) that releases refrigerant if—for whatever reason—the system becomes over-pressurized. It's a safety device and so it should be left alone.

There are no separate chambers per se inside the compressor, so there's no need to worry about that. The oil circulates with the refrigerant throughout the entire system, including all of the compressor's internals.

As for refilling the system with the correct amount and type of oil specified, you can put all of it in the compressor as long as you rotate the main-shaft by hand about 12 times, using a wrench for leverage if needed. Or you can employ the oil-balancing method: 3/4 ounce in both the condenser and evaporator, 1/2 ounce in the R/D, and the rest in the compressor, rotating the main-shaft by hand as described above.

[knotworking]

I loaded the rest of the Freon into the system, blowing super-cold now, here's my gauges running the air at it's coldest setting:


unfortunately, problem still remains, clutch won't engage without shorting the relay.

A little more backstory that might give some insight, I haven't been running the AC since it went out almost a year ago. I tried adding the refrigerant with dye you get from the automotive store back then to find any leak, but it never appeared when I searched with a black light. I tried to run the AC multiple times after that, but gave up after only hot air blew out When I was blowing out the hoses on Wednesday, all the dye shot out of the Lo hose, it seems all of it just stayed right where I injected it at (the hose expands to a larger, round cylinder at the low pressure nozzle, pretty sure it accumulated right there).

I'm thinking now that this current clutch issue wasn't just introduced by my changeout, it was probably the reason my AC stopped blowing cold last year.
Maybe I have a bad switch or some wiring that is damaged. I could only find one video on testing switches (wasn't really helpful), are there any tips on testing those? I'm assuming, since shorting the relay works, that I don't need to test the electrical wiring coming from the relay to the compressor. What would you recommend the testing steps be to try to isolate the bad switch, wiring, connectors, etc.,? I have a multimeter to test everything with.