Another AC Problem

F

Fuzzy Fingers

New member
2003 V8 SR5 2WD with 150K.
Used the search button zealously and did find some solutions. Unfortunately, the didn't work for my issue. Started off with cold air then barely cool air then cold air. Had system vacuumed down and recharged. Still happened. Found the thread on the Evaporator Case Sensor and replaced it. Still cycling.
Had my buddy bring out his gauges and assorted toys to check through it again. Appeared to be over charged somewhat so bled it down. Ultimately, when running max ac and running fan on high, the compressor doesn't cycle. If I reduce the fan, the duct temp (close to the core) gets to 45 degrees, the compressor cycles off. Warms a little then compressor kicks back on and so forth. If I am using fresh air, I can reduce fan speed but the air is fairly warm since its 90 plus outside. We watched for pressure changes for the expansion valve doing anything. We were unable to see any dip in pressure as it got colder in the evap case, then the sensor would open and cycle the compressor. Ultimately, the evap case is getting too cold.

There doesn't seem to be a leak anywhere and pressures on high and low side were good when running at 1500 RPM and and idle. I don't understand the expansion valve function but the current guess is the valve is stuck open and unable to close. Anyone with any ideas? Moisture in system? Blockage? (Doesn't seem to be the case based on pressure)
 
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For anyone else having similar issues, the problem is identified as a stuck expansion valve. Book is 5.9 hours of labor. One of those jobs that those of us with less shade tree skills, probably farm out. Extra $150 for dealership to do it. They said they will use my parts though if I bring them. Dealerships wants $299 for evaporator and $85 expansion valve. Can get both on Amazon for $100.
 
The dealership and two other sources all believed expansion valve was the issue. I have now replaced the expansion valve and evaporator coil. The compressor is still cycling off too long allowing the air to become quite warm before the compressor turns back on. I have replaced the thermistor based on another poster's experience as well. None of this has changed or modified the issue.
If anyone here has used the gas pedal judiciously, you'll notice the AC blowing a little warm due to the surge of Freon into the core causing it to get cold enough where the compressor stayed off for some time. I deal with this condition all the time if the fan speed is lower than FULL. The core simply is getting too cold and the thermistor opens for a while until the "ice" is melted off the probe is what it seems to be doing.

Can a compressor be working too well pushing too much Freon? The pressures all seem to read good and I currently have 1.3 lbs in the system. System calls for 1.2 to 1.4 lbs. Does not seem to be related to the temp controller either. Issue happens in manual and auto.
 
What pressures are you counting as good? IIRC 32psi or so is max in these guys, low side, right up front. I'd have to look again to confirm. I had somewhat similar issues upon purchasing mine and I undoubtedly over charged her in attempts to fix. Got worse. Dropped down to correct pressure, regardless of volume, added some leak stop, been great for a few months now.

Was the system vacuumed before refilling after replacements?

Clean the ac switch?

Just ideas...hopefully it's some help
 
Low side runs between 30 and 35 depending on the heat of the day. High side was above 250 but not over 300. The system has been vacuumed several times. Likely any moisture is gone. Switch is fine and engages as soon as I command it using both the temp control panel and when jumpering the thermistor connection.
Thanks for the suggestions. I'm kinda at the end of my knowledge.
 
there is also an expansion valve/orifice in AC systems. i remember reading that little bits of schmutz or whathaveyou can either completely clog it or severely restrict it. i doubt this would still be the case with all the fills, vacs, etc, buts its a thought.


the other thought is that maybe our babies just dont have great performing AC systems. i come from an 03 accord that blasted freezing air so my 4runner leaves me desiring more.
 
So you can watch the air vent temperature changing with a thermometer?

By any chance does the blower volume change as well? I recall a TSB that stated something about the blower housing freezing.
 
Sub'd. I too have some AC issues. Mine is a wee bit different. With my AC (most noticable on high) on I can tell a temp change of maybe 10 degrees of the air blowing for about 3-5 seconds then it starts to get cold again. You can almost smell "moisture" when it happens. Sorry but that is the best way I know to describe the smell. It has me baffled. Local shops here say everything is fine. They tested it, vacuumed it then recharged it. It still does it though. Something is definitely up. May be a different problem from what OP has but there is still good useful info here and I want to learn!! Also, I know there are threads on here saying a relay for the compressor is a culprit in certian cases. If I remember correctly most say their ac button would blink. Mine never has but I still have the wrong relay. Guess I should start by replacing that. Just a thought.
 
BlackWorksInc said:
So you can watch the air vent temperature changing with a thermometer?

By any chance does the blower volume change as well? I recall a TSB that stated something about the blower housing freezing.
Click to expand...

I have checked the vent temps. We fed a line down almost into the core and it would get to about 44 and the AC would cycle. The temp would generally come up about 20 degrees before the compressor would cycle back on. I have never noticed the change in blower volume or amount of air flow. It simply gets warm, then the compressor turns on again and I have cold air until the next cycle.
 
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zonianbrat said:
Sub'd. I too have some AC issues. Mine is a wee bit different. With my AC (most noticable on high) on I can tell a temp change of maybe 10 degrees of the air blowing for about 3-5 seconds then it starts to get cold again. You can almost smell "moisture" when it happens. Sorry but that is the best way I know to describe the smell. It has me baffled. Local shops here say everything is fine. They tested it, vacuumed it then recharged it. It still does it though. Something is definitely up. May be a different problem from what OP has but there is still good useful info here and I want to learn!! Also, I know there are threads on here saying a relay for the compressor is a culprit in certian cases. If I remember correctly most say their ac button would blink. Mine never has but I still have the wrong relay. Guess I should start by replacing that. Just a thought.
Click to expand...
Zoni,
You and I seem to have a similar problem. I too can smell the moisture when it warms up. This is because the compressor stays off too long. The only think I understand is that the thermistor when it gets to 32 degrees, opens and shuts off the compressor. Once it warms above this, the circuit closes and the compressor once again turns on.
Regarding the relay, mine has the newer relay and the issue happens based on core temps. If I run mine wide open, it doesn't cycle as much but when it does, it gets very warm before getting ultra cold.
 
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BlackWorksInc said:
I'm sorry if I am asking obvious questions...

Is the evaporator box draining properly?
Click to expand...

I'm not offended at all. The box streams almost a continuous stream when running fresh air. I'm down in Georgia so its a little swampy and plenty of condensation on AC line as well.

Just got back from a AC "specialist". He say he can't find a problem but thinks it is electrical and asked for the truck for a few hours so he could check ohms. What else is there? The sensors on AC compressor and the temp control panel?

I understand about enough of this stuff to be a danger to myself and those around me but when it comes to AC stuff, even Bush League is above my level. Trying to not have my wallet shriveled to badly by this process. I appreciate any input or help.
 
Hope the specialist can shed some light on our problem Fuzzy. Please keep us updated and i sure hope it isnt an expensive fix. I hate dealing with these AC systems. Dad recently told me he spent 3 grand on his car ac system. Started having what I thought was a minor issue but he told me in his experience once a component starts causing problems they start coming one after another so he had the dealership replace almost everything so it was a new system that was warrantied. He lives in Alabama so I feel for you Fuzzy you have to have AC there.
 
This guy is convinced it's electrical. No tremble on gauges, pressures are where they should be, AC cycles off when it should. But he sees what I've been after where the compressor doesn't come back on soon enough to keep the air temp stable. I will definitely report back. Hopefully he identifies the fix.
 
Well AC guy went through it electrically, checked ohms on compressor. Pressure is good. Everything behaves properly, the AC when it cycles simply takes to long to come back on. I felt bad since he spent some time on it and wouldn't charge me. However, he acknowledged there was something going on with it.

The thermistor, should that black tip remain on it or should it be removed? That is the only place where I can a problem happening whereas the black tip insulates the sensor that opens and closes.
 
Hmm... if it's electrical you're either looking at the control unit or the A/C Amplifer... which I don't really remember what it does because I haven't had to replace many of them. lol

I'll see if I can find some information in TIS regarding it.

Post Note-

So TIS didn't exactly differentiate how the A/C Amplifier Differs from the Control Head, seems to be the module that handles the input/outputs of the A/C side of the HVAC system. Still looking into it...

Update-

Looks like the basic difference is that the A/C Amplifier is the control unit for the HVAC system, while the Control Head is mainly for the automatic functions. The wiring diagrams and course books are a bit vague on the difference and for the life of me I can't seem to remember how it was explained a long time ago. (Don't get too many oddball A/C issues that are this electrically involved.)
 
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AC amplifier? Is it part of the control panel? If it is a reasonable fix, I'll throw a few bucks at it.

The AC guy says the temp controller works properly. Auto seems to work fine. The temp fluctuates because the compressor is off too long but it recognizes ambient temps and if the AC is supposed to be on or not. I'm guessing by switch position.

Update: Used search function. Expensive part but looks easy to replace. Question, is there a way to test before I fire a $300 part at it.

PSS. Found used part but suffix doesn't align. How do I check comparability? Used part# is 88650-35231 Came from 2005 4runner. Toyota parts diagram calls for part# 8865035190 for a 2003 4runner.
 
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Have you had any luck with this Fuzzy? Im pretty much relying on this thread to diagnose my problem because the small town I live in I dont trust the mechanics at all.
 
I also been having this issue. One conclusion i came up with by observing a few things. My v8 t4r has the A/C line running on top of the Exhaust manifold, Causing a large amount of heat. Sometimes, I feel the lines and it does get warm even with the A/C running. So my Plan is to get some high temp Gold heat wrap and wrap those lines, only problem is that water will build up over time possibly causing corrosion.

2: I do have an exhaust leak that could also cause the A/C lines to heat up.

I will Wrap the lines tomorrow, and see if there is a difference.
 
dirty monkey said:
I also been having this issue. One conclusion i came up with by observing a few things. My v8 t4r has the A/C line running on top of the Exhaust manifold, Causing a large amount of heat. Sometimes, I feel the lines and it does get warm even with the A/C running. So my Plan is to get some high temp Gold heat wrap and wrap those lines, only problem is that water will build up over time possibly causing corrosion.

2: I do have an exhaust leak that could also cause the A/C lines to heat up.

I will Wrap the lines tomorrow, and see if there is a difference.
Click to expand...

Hmm, hadn't thought of that... let us know how it works out?

You should only have to wrap the lines to the evaporator.
 
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