A/C coming and going, please help diagnose, it's 104 degrees

M

madetomeasure

New member
Ok,
I've read some of the recent threads on A/C that have come up. I work on my own cars, but I've never played around with A/C before. Fortunately, my neighbor has replaced an entire AC in his driveway and he'll be helping me as soon as I get this diagnosed. If y'all could narrow this down.....
What I know:

Intermittent cooling -- blows cold(ish) for sometimes 3-4 days straight (If it just weren't cooling, I'd go get it charged and call it a day.) Then it may not work for 2 days, then it might work again.

When it decides to 'quit' it will start by blowing condensation out of the vents like crazy. looks like smoke. I'll turn the AC off -- when I attempt to turn it back on, hoping it will start cooling again, it will make a chirp kind of noise (sounds like its likely some kind of blend door maybe...) Then I hear what I believe to be a clutch on the compressor or something make a noise every few seconds, like a mechanical buzz-- sounds like it is attempting to start but is stuck.

A couple of months ago, when summer was just getting rolling here in Texas, I noticed poor cooling, so I got a 22oz of R134a and filled the low side. It took the whole d@*& can, and never sent the gauge into the green zone.
I assume this truck is sitting around 26oz of total capacity, so I must have a mega leak right?

Engine is not overheating, so I don't think it's a fan clutch, but correct me if I'm in error.

Thanks for any help you can offer.
 
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I think getting the pressure readings are your best place to start.

Don't be intimidated by a/c work. Having good help makes it really easy but it hasn't been so bad for me so far.

I had different symptoms but also intermittent cooling over a year ago and I figured it was my expansion valve. I replaced that and my drier and it has worked great since. When I opened it up to replace the parts I saw how dirty and plugged my evaporator core was. I'm sure that contributed to bad A/C performance. It's 102* right now and the air coming out of my center vent was 48* last time I was in the car. Not trying to brag but I thought that might be good motivation for you. Good Luck!
 
I'm running into issues with my A/C unit as well so I have been doing a little research. Heat and JBurt are right. Get the pressure readings first and the will lead you in the right direction from there. You want to be careful with overcharging your system. I believe I read that overcharging can cause damage to your system as well. I believe the 3rd Gen A/C systems only hold 1.8 lbs of 134a. So...about 28.8oz. Based on the intermittent cooling though, it sounds like it might be the expansion valve.
 
When you are talking about condensation or "smoke" does it smell like refrigerant or does it just smell like musty water? The reason I ask is this could be an indication of either the Evaporator Core itself leaking or that it is icing up which would cause a similar effect, just less poisonous.

As for the specifications; Refrigerant Charge Volume R134A 650 ±50g (22.92 ±1.76oz) according to TIS's FSM.

A common problem with the A/C units on Toyotas it seems is the magnetic clutch relay failing, or sometimes the clutch itself.

The best place to start will be to check your static pressures after leaving the vehicle to sit for a while, this will give you a rough idea of what is in the system (rule of thumb generally is something like 1psi per degree of ambient temperature with the system off and left to equalize with the surrounding air), though you're measurements may be a bit off if ambient is 104*F.

While you're at it check your relay and see if its working properly and replace it if you have an extra to double check.
 
well.... yeah definitely get pressures for us on low side and high side. We'd like to see:

vent temp
High side (red) psi
low side (blue) psi (cycling range. min/max)
ambient temp
humidity (just a guess)
 
mikebontoft said:
well.... yeah definitely get pressures for us on low side and high side. We'd like to see:

vent temp
High side (red) psi
low side (blue) psi (cycling range. min/max)
ambient temp
humidity (just a guess)
Click to expand...

edit: if it's easily accessible, see if you can find a spec for the compressor clutch air gap. I replaced an AC compressor yesterday on a vehicle that had intermittent cooling. the air gap was .6" and max was .33" sometimes it just got out far enough that it wouldn't engage.

I kind of doubt that's the problem here, but I won't know till we get some info.
 
ok, below is the pressure at about 1500rpm, 60l/300h


pemyduvy.jpg
 
Last edited:
and here is when the tech took it up quite a bit, maybe to 2200 rpm or so. lo side hit about 50, hi side got to 450, (pic only shows 400+)

anatebup.jpg
 
his indication is that he is pretty sure I have a blockage in the condenser.

he also thinks my compressor is getting weak, not gone yet, but weak.

vent temp was 50, and stayed that way the whole 30 minutes in the shop... of course. couldn't replicate the intermittent failure I get while i was there.....

ambient temp right outside right now is *only* 94 degrees with humidity at 40%
there was a nice big shop fan in there, blowing right at my car so it was probably only 80 degrees near my car, but it had just been driven in...

one thing I think now is that I overcharged the system when I put that WHOLE TWENTY-TWO OUNCE CAN in.....
 
high side is too high, low side is too high. recover and evacuate the system for 30min and refill to the proper refrigerant amount.
 
With a high side of 450 you're compressor is no where near weak... Like others said recover, vacuum for 30 mins or so, and recharge with proper amount... Replace your receiver/dryer while you're at it... If you still have similar readings afterwards I'd take a look at your fan clutch... You can spray the condenser down with water to simulate more airflow as well to help rule out a stubborn TXV
 
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