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Old 08-12-14, 07:39 PM   #1
t2d2
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Default A/C refrigerant level

I'm finally getting down to some of the smaller items on my list of things to check/fix.

My A/C works well except when idling in Drive, where it creates RPM dips and some pretty heavy thuds. But if I put it in Park or Neutral, the RPMs rise enough that it doesn't happen. Once rolling, it's a non-issue.

The factory service manual has a checklist on AC-103 for using the sight glass to determine refrigerant level.

1) bubbles present = insufficient
2) no bubbles present = none, sufficient or too much
3 & 4 deal with temperature differentials
5) immediately after A/C is turned off, refrigerant stays clear = too much
6) immediately after A/C is turned off, refrigerant foams then stays clear = proper

I checked on that today and I have lots of bubbles present in the sight glass (#1). However, when I turned off the A/C, the sight glass was clear (#5). I'm wondering how immediate "immediately" has to be... As in, can one person conduct the test or has too much time passed between turning off the A/C and getting back to the engine bay in order to see the next step?

Also, I'm confused how either #5 (too much) or #6 (proper) is possible if #1 (insufficient) is observed. If not for that contradiction, I would feel comfortable just buying one of the recharge cans and topping it off. Otherwise, I might be better off taking it to a shop to have them inspect it closer.

Oh, there is an asterisk for #1:

"Bubbles in the sight glass with ambient temperatures higher can be considered normal if cooling is sufficient."

The temperature at the time of testing was 75 degrees. Is that considered a "higher" ambient temperature? Cooling can only be insufficient with higher temperatures, so what does that leave? That wording is pretty vague.
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Old 08-12-14, 10:06 PM   #2
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Lexus master tech here,

You are putting too much thought into this. Basically if you see bubbles in the sight glass while the a/c is on at idle, it is under charged. Your best bet would be to take it somewhere to get an evac and recharge (make sure they vacuum for at least 30 minutes); or you could try to add refrigerant yourself. Most Lexus vehicles take around .5-.75 Kg of refrigerant (full charge). A yellow sticker under your hood should tell you the correct amount. I would try to add in slowly some refrigerant until the sight glass becomes clear.
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Old 08-12-14, 10:13 PM   #3
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Much appreciated, thanks.

This is my first time doing anything with an A/C system, so I'd rather make the mistake of over-thinking than under-thinking it. Bubbles bad, got it! Just for the sake of my education, can you explain the significance of #5 and #6?

The manual says 950 +/- 50g, but I don't know if that applies to all years of SCs (post-'92 with Freon, that is). That's a fair bit higher than your figure.

I'd be stoked if my A/C idle issue turns out to be nothing more than low refrigerant, rather than something like the compressor.
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Old 08-12-14, 10:26 PM   #4
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Oh shoot, I overlooked something obvious. The chart is actually a tree, with the remedy column referencing what to do next. No bubbles present (#2) = refer to #3 and #4. Noticeable temperature differential (#4) = refer to #5 and #6. So, #5 and #6 are n/a in my case, because only #1 applies.
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Old 08-13-14, 02:27 PM   #5
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I was quoted $150 for an evac and recharge, so I opted for doing it myself with a can of A/C Pro. I thought the 20 oz can would be more than enough, being 60% of the car's rated capacity, but either my system was way lower on refrigerant than I figured, or it's got a leak... It started at 12 psi and topped out at maybe 15, well short of the 27-47 psi target range. Is it normal for the psi to stay low like that until the system is close to full?

However, the sight glass is now clear of bubbles and: 1) the thuds while idling with A/C on are significantly minimized, and 2) cold air at the vents (with A/C off) is blowing only 1 degree warmer than outside air! That would be a huge relief if my issues with the cold air being warmed 20+ degrees are somehow intertwined with a low refrigerant level. (Makes no sense how that would be, though, with A/C turned off. Anyone??) I can stop breaking stuff while pulling apart sensors and connectors, in that case...

I'll leave it as-is for a couple days and see if it holds there, in which case I'll buy another can and try topping it off. If the pressure drops back down and the symptoms return, then I wasted a bit of money on can #1 and will need to take it to a shop for serving, after all.

Edit: Another possibility is the gauge is defective. That would suck, as I wouldn't know if I over-filled. I might have to see about borrowing a gauge from someone else to check, or see if the store has a spare for that purpose.
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Old 08-13-14, 03:42 PM   #6
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I did alllll the same steps as you back in May. I ended up getting a small can of refrigerant with leak stop mixed in, then another larger can with a built in gauge. I used both cans until empty and it held suffice pressure and was coldish until I sold it. The only REAL way is to take it in, pressure test the system for leaks and a full recharge. As someone said, it should be left on the machine for a full 20-30+ minutes to notice any pressure changes. Even then it may not be totally sealed, mine leaked out over the winter from last summer when I had mine serviced.. The idea is to get to negative pressure (vacuum) and let it pull in the refrigerant on its own instead of forcing it in. I recommend getting a seal kit from Toyota/Lexus and replacing the o-rings. Is your compressor turning on? Making any noises?
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Old 08-13-14, 04:42 PM   #7
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Thanks Kris, that makes me feel better. I got the kind of recharge can with the separate gauge so I've got that for future uses. My compressor is running fine, and I didn't notice any noises. My guess is it's like 80% full and functional as-is, but not quite full enough to hit goal pressure.

Firestone has a $9.99 A/C inspection special this month, so it's probably worth going in there to rule out any obvious leaks before I add more.
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Old 08-13-14, 06:33 PM   #8
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Ok, let me get this straight right up front! I am a female with hardly any mechanical abilities. That says it all right there. I have an 1992 SC300 1st Gen, 2jz-GE in line 6 engine. I have been adding R134 refrigerant to my car for over a year, just limping along trying to keep it cool. My neighbor, who is an industrial A/C technician.and he has been the one helping me, always puts the gages on it, etc. Finally, after several cans of coolant over the last 6 months, I finally took it to a mechanic to repair the a/c leak I know I must have had. They replaced an a/c regulator, vacuumed it down and recharged and also added dye so they could see if there are more leaks in the future. A/C regulator was $799.46. Labor for 3.00 hours was $210.00 (which I realize is pretty reasonable in this day and time) and 2 units of freon at 29.99 each. All told, with tax, final total was $1140.30. Did I get ripped off? As an aside, after this repair, my car no longer idled and cut off immediately, which I feel was caused by some of the work they did. However, the mechanic informed me it was a "usability" issue and I would have to bring it back to address that problem. I had to have it towed back because it quit and would not restart. This time he replaced a TPS and an ignition module. Cost for the TPS was 107.34, Ignition module 274.04 shop supplies of 10.00, 3.00 hours of labor for 210.00 plus the tow bill of 60.00 plus tax for a total of 659.89. It is STILL not idling and STILL cutting off. I can't even drive it after $1800.19 spent!!! I'm not a rich person and I love my car but it is becoming a cash cow that I cannot afford. I've had since 2001. It's only got around 187,000 miles on it. If I choose to replace it, the most I can afford is around a $4000.00 car. I keep my Lexus because after all the intermittent repairs I have done on it over the years have probably been enough to buy a new car, but I know what has been done to it. Buying a $4000.00 car, to me, is just buying someone else's problems. I realize the issues with the not idling and cutting off probably needs to be addressed in the Performance forum, but since it all started with the a/c I thought I would start here. I have no mechanically inclined people that I can trust, so I come to you. Hope you can offer me some input and suggestions. Thanks!

Last edited by rpcsc300; 08-13-14 at 06:38 PM.. Reason: To correct some misspellings.
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Old 08-13-14, 07:10 PM   #9
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Ouch, that's an expensive bill. The labor rate and refrigerant amount are fairly standard charges, but the parts cost was quite high. I would have shopped around for a used or reman'd part to cut $400-500 (?) off that.

I have no guesses as to what the mechanic might have done to cause the additional problems, but I would take the approach of saying they shouldn't be charging you labor to fix their mistakes. Then shop around for better parts prices to minimize those expenses. For example, you can buy a used TPS for under $20, or an OEM new one for $50. There's some serious markup at $107, even if that included labor.
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Old 08-13-14, 10:30 PM   #10
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Dear t2d2: I really appreciate your reply. Needless to say, I almost fully expected your reply. I really got ripped! I was going to report this shop to the Better Business Bureau, however, all they do here in SC is send a consumer complaint to the business and they reply directly back to the consumer, not to the better business bureau. I already know what he's going to tell me because I challenged him when I had to have it towed back down there when it wouldn't idle and cut off. I KNOW with almost complete certainty that the work they did on the a/c directly caused the second problem with the idle and cut offs. However, as I said before, it's a well known fact that women that have no clue about mechanical problems are usually taken advantage of by unscrupulous mechanics. (I'm not dissing all mechanics, it's just that I haven't a good one yet). In 2011, my car was all over the road and another mechanic advised the long bar under the front of the car between the wheels of the steering assembly had almost completely broken in two and it needed lower control arms on each side. Total price to repair: $1800.00. I asked him if I could find two lower control arms, would he install them and he replied that he could only get them from the Lexus dealer. At least in this incidence I came to this forum and researched lower control arms. I discovered from one of the posts that the steering assembly was exactly the same as on the Toyota Supra. They had mentioned Carson Toyota in California sold them and they guaranteed them to fit my Lexus. I purchased them for around $500.00. The Mechanic had quoted me $900.00 for those. So I am really grateful for the help I received from this forum then. I also appreciate your reply now, even though there's absolutely nothing I can do now but advise everyone I know NOT to take their car to the mechanic that worked on my a/c. They say what goes around comes around, so perhaps things will come back around to him the way he has treated his customers. In the future, I will come here and mention symptoms before I ever take my car to another mechanic. I know the folks here are far more trustworthy than any mechanic I could possibly find here where I live. God bless you and thank you again for your reply.

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Old 08-13-14, 11:05 PM   #11
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My current mechanic is a mobile guy who saved my butt when I needed to have the car towed to a shop for a fuel line problem. He charged me less than the tow truck alone would have. I now go to him for everything, and for most stuff he's happy to have me working alongside him, learning as we go and lending a hand where I can. You might do well to look for someone like that. Not only will you be more comfortable dealing with these car problems, but you won't get duped with false reports of bad parts and repairs performed when the person is right there showing you what they've found. As an added bonus, the hourly rate will probably be quite a bit lower.
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Old 08-14-14, 12:21 AM   #12
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Thanks, t2d2 and ClassicSC3. I pray that one day I'll be able to find such a mechanic as you have! It's alll by trial and error with me. I ask other Lexus owners who their mechanics are and most of them take theirs to the dealers because they have much newer models. I would be so happy if I could find just a "shade tree" mechanic that I could trust! Truly, you are both fortunate. Also, as you say, if y'all do have a great mechanic, thank your lucky stars and do let them know how much you appreciate them. (which of course I know you do!) BTW ClassicSC3, I noticed you show your location as Lonestar...would that perhaps be Lonestar, SC? If it is, perhaps you can shoot me a message and let me know who your mechanic is. Lonestar, SC is only around 60 miles from me. Blessings.
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Old 08-21-14, 02:41 PM   #13
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I took the car in to Firestone today to take advantage of this month's A/C Performance Check special (75% off!), and sure enough, my system is leaking at both the High and Low schraeder valves, plus two o-rings at the compressor. That probably explains why I couldn't get hardly any pressure building up with the recharge can. Hopefully, it also explains why my heated cool air returned a few days after initially staying at outside air temp after the recharge.

There must be some sort of safety feature that allows coolant to circulate, or keeps blend doors open, to protect the condenser/evaporator when refrigerant is low? That's the only explanation I can come up with. I guess I'll know for sure once I've got the leaks repaired and the system recharged.

The initial recharge can (~$20) was a waste, but at least they caught that one of my license plate bulbs was out. And I happened to have a #168 spare at home, so that $14.99 "repair" quote basically offset things in some sketchy accounting perspective and only required a couple minutes of my attention to change.
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Old 09-02-14, 11:02 AM   #14
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I dropped off the car this weekend with my mechanic to have the leaks fixed. He was surprised to see the system holding at 75 psi and no indication of leaks. Additionally, the A/C is blowing 48 degree air on an 80 degree day (previously got no lower than 68 degrees on ~90 degree days), and MAX COLD without A/C is holding steady at outside air temp. When I added my can of refrigerant, it topped out at 15 psi on the same gauge and then leaked down from there. No bubbles now in the sight glass, despite them being there when Firestone did its inspection. This is a real head scratcher.

Either the leak sealant in the can I added took a week to do its thing, or something Firestone added to the system as part of their A/C performance check (presumably, they add something along with dye, if that's the method used, to pressurize the system enough to check for leaks) topped it off. If it's #1, then how did the pressure increase so significantly from 15 to 75 pounds? If it's #2, then why wasn't I charged $30-70 for enough refrigerant to top it off?? I can't make any sense of it, but I'll keep an eye on things for a few days and count my blessings if it holds solid.

Actually, I did just come up with one semi-plausible scenario. Maybe the leaks weren't really there and they topped off the refrigerant to do the test, using the need to "repair the leaks" as a way of covering that cost and then charging for the already-done evac/recharge at the same time? You would think they would have pressured me to get the work done at the time, though. Then again, I've been a customer there for a long time. And I had told them ahead of time that I just wanted the inspection done for now, so as to determine the next step.
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Old 09-08-14, 07:56 PM   #15
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Good grief, things get even cloudier...

Today, my MAX COLD air is reading 103 at the vent on a 75 day, and Max A/C was holding in the mid-60s before eventually working its way down to 58 and staying there, as opposed to last week's 48 on a 80 day.

The sight glass is still clear.

I'm so confused by this bipolar system.
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