AC - Can't Charge with Freon

Happy Friday to all the fine folks of TW. I've been helping a buddy of mine try to get his AC fixed. The truck we're working on is a '98 Tacoma V6 4WD. His system had no freon, due to his condenser being bent/cracked (from driving over some thick brush with no skid plate).

So we replaced the condenser and the receiver/dryer. Then we pulled a vacuum on the system and it held with no leaks for an hour or so, so we went about trying to charge it. We can't seem to get it to take more than 80-90 psi into the low-side, and then nothing into the high side.

We hypothesized that perhaps the compressor was seized up (although we can spin the clutch by hand up front) as it won't seem to kick on during the charging process. We did however jump the magnetic clutch, and that engaged properly. That still didn't seem to get the compressor going, as the engine didn't idle up at all after jumping the magnetic clutch.

Should we look at replacing the expansion valve or compressor next? What other things might we be overlooking.

 

Not an expert but you go by grams, not PSI. Check the sticker under your hood
If it's not holding pressure, probably should get some dye and check for leaks

 

So to clarify it's just not really up-taking adequate freon and not transferring freon from low pressure side to high pressure side. Basically wondering what are the likely culprits that would cause that? Compressor? Expansion Valve? Other parts? I'm far from an AC expert.

Regarding the grams/oz. of freon it's taken, it's very minimal, and much less than the 1.4 lbs the system requires. We weighed the can we hooked up and could only get the system to uptake a couple of ounces. The system does hold a vacuum though, so I don't feel a leak is likely at play.

 

Do you have the correct dispenser?

The cans used now require a new dispenser with a trigger.

The pierce type dispensers no longer work on the new 134a cans.

 

*** DISCLAIMER**
I have recently read that it's not a good idea to charge the A/C system while the engine is running. Below is my experience but please do more research before trying this.

My A/C once leaked out all the R134A and I discovered the same thing - the compressor clutch would not engage when I tried to charge the low side port with a DIY can of refrigerant. So with the engine running, I jumped the positive battery terminal to the (+) terminal of the compressor and that got it running and it then would take the refrigerant. I believe that the pressure switch is wired in series with the A/C magnetic clutch and so if you short out the pressure switch, the compressor will run and uptake the refrigerant.

Also, here's a thread from a guy that replaced his entire system in case you need it:
https://www.tacomaworld.com/threads/1st-gen-a-c-system-replacement-how-to-seized-compressor.293204/

Good luck and be safe.

 

That's interesting to know. We've been using the pierce type. Will definitely look into this. Kinda bizarre that O'Reilly's has a wall of R134a cans with a small stash of pierce type dispensers right next to it

 

Once the system has drawn out enough freon, you can put the can in hot water to get the rest (I just do it all on a scale). However, 80-90 psi isn't right. With engine running and compressor engaged it should be much lower than that.

> We did however jump the magnetic clutch, and that engaged properly. That still didn't seem to get the compressor going, as the engine didn't idle up at all after jumping the magnetic clutch.

I don't get it. With the engine running, if the clutch engages, the compressor should be turning as well. If it is, and you're still seeing 80-90 psi, I'd suspect a blockage somewhere.

 

Good recommendations here, but I would just add that an hour or two isn't a good test of leaks, ya wanna hold a vacuum for as long as you can wait. I always try for at least 6, overnight if I have the time.

 

If it holds vacuum that doesn't rule out a blockage?

If we jump the clutch and the engine never idles up, what's up with that? Per the FSM no engine idle up in that scenario points to wiring harness or AC amplifier.

Could the AC amplifier somehow be a culprit here?

 

Yea I kinda figured that. But in reality if it holds for an hour or so, then won't take freon, that at least rules out a major leak causing it not to charge up properly right?

And back to no engine idle up when we jump the magnetic clutch, that seems to be significant to me. Is it the compressor that ultimately moves freon from the low pressure to high pressure side? Can that happen at 725-750 rpm?

I'm kinda clueless when it comes to AC to be honest

 

Yes, the compressor would have no problem circulating refrigerant at 750 rpm. When I engage the compressor, I don’t see much of an idle jump, maybe 50-100 rpm max if that.

If there’s a blockage in the expansion valve or elsewhere, you could be pulling a vacuum on one side only. Are you seeing the vacuum on both low and high sides?

 

I can't honestly remember off hand. I think there was noticeably less vacuum pulled in the high side, but can't swear to it (we've paused that project and left the truck sitting for a couple weeks now). We were already thinking evaporator and expansion valve would be the next parts cannon shot at this.

 

The lack of idle-up makes sense since you are just triggering the clutch, the ECU isn't involved so I would not expect the idle to raise.