Air conditioning not cooling at idle

[Jeremy556]

When sitting still, at idle, the A/C will only cool to about 8-10f degrees below ambient temp at 100f. Vent air temperature will climb from 42 to 90 degrees f at a rate of about 1 degree per 5 seconds when set on max fan speed and non-rec, setting rec slows the temp increase by about 3-4 times. Pressure on low and high side go up and off the gauge when this happens.

At 1500rpm, sitting still, no problem, gauge readings are like 26/240, vent temp is 40-44f and the compressor cycles regularly, even at 103 ambient. I can coast down a very long hill for 30+ minutes at 15-30mph speeds with the engine in neutral, and maintain normal operation. So airflow over the condenser anywhere above idle speed from the radiator fan is enough.

These would lead me to suspect the fan clutch, however coolant temp never varies significantly (actual reading from Techstream, not the idiot gauge on the dash). I also can't stop the radiator fan when coolant temp is at operating temperature.

I have evacuated/charged and pulled vacuum between on the system twice, no change in operation or readings. It also held vacuum for over 12 hours, so no leaks.

Magnetic clutch on the compressor operates normally and all of the techstream active tests produce expected results, no stored codes.

I am pretty ignorant of cooling systems and am at a loss at this point. Hoping to avoid throwing parts at it until I find a fix, as many of these components are not cheap nor quick/easy to install.

 

[Jeremy556]

Also, no unusual externally visible damage to the condenser. Maybe 3-5% of fins are bent or blocked by debris. Tried rinsing and even cleaning with a condenser coil cleaner with no noticeable difference in operation.

 

[BlackWorksInc]

This only happens at idle? Hmm... How many miles you got on this thing Jeremy? Have you also looked at what the IAT (the one infront of the condenser) and the Evaporator temps are doing? I can't recall if you can, but I think you might be able to see what the Evaporator Core Temperature Sensor is seeing as well as the room temperature sensor.

Also is this with the "AUTO" setting on or just straight "MAX A/C" only?

 

[(none)]

This is after driving around for a while? How warm is the coolant while youre having the stationary AC issue? Does it get any better when the coolant is hot (190F)?

The clutch fan wont engage until it gets warm enough air, so if the radiator isn't up to temp, the fan won't engage. Id say if when you rev up to 1500rpms everything is good, you have an airflow issue. Has it always done this or is this new this year? easy and relatively cheap solution is to just replace the fan clutch and see if that helps. modification option is to add an electric pusher fan to the front of the radiator which runs when the a/c is on. The GXs have those (as well as many other vehicles with the mechanical fans, for the same reason). That big fan can only pull so much air at 900 rpm while idling.

 

[Jeremy556]

This only happens at idle? Hmm... How many miles you got on this thing Jeremy? Have you also looked at what the IAT (the one infront of the condenser) and the Evaporator temps are doing? I can't recall if you can, but I think you might be able to see what the Evaporator Core Temperature Sensor is seeing as well as the room temperature sensor.

Also is this with the "AUTO" setting on or just straight "MAX A/C" only?

Yep, idle only. 185K. IAT is running about about 20 degrees above ambient temp. Not sure where to see the evap temp.

 

[Jeremy556]

This is after driving around for a while? How warm is the coolant while youre having the stationary AC issue? Does it get any better when the coolant is hot (190F)?

The clutch fan wont engage until it gets warm enough air, so if the radiator isn't up to temp, the fan won't engage. Id say if when you rev up to 1500rpms everything is good, you have an airflow issue. Has it always done this or is this new this year? easy and relatively cheap solution is to just replace the fan clutch and see if that helps. modification option is to add an electric pusher fan to the front of the radiator which runs when the a/c is on. The GXs have those (as well as many other vehicles with the mechanical fans, for the same reason). That big fan can only pull so much air at 900 rpm while idling.

Coolant is generally right around 200f and the fan clutch is engaged. This is a new issue.

 

[BobsTrail]

If the problem will show at home in the driveway after it's warmed up, I think I would put a fan, like a 20 inch box fan in front of the grill and see what happens. Even though the fan clutch appears to be working, it may not be spinning the fan fast enough due to slipping. If that helps, change the fan clutch.

 

[Jeremy556]

Even though the fan clutch appears to be working, it may not be spinning the fan fast enough due to slipping. If that helps, change the fan clutch.

That is exactly what I am thinking.

I haven't got a fan that will produce significant airflow, but I can spray some water on the condenser and temps/pressures return to normal until all of the water evaporates.

The fan produces a strong flow of air and I tried stopping it with some pretty stout cardboard, which it absolutely shredded without even slowing down. I figure it could probably do that, even with significant slipping.

I plan to try to obtain a local fan clutch tomorrow, plus an electric condenser fan on the way.

 

[rigtec]

"When sitting still, at idle, the A/C will only cool to about 8-10f degrees below ambient temp at 100f. Vent air temperature will climb from 42 to 90 degrees f at a rate of about 1 degree per 5 seconds when set on max fan speed and non-rec, setting rec slows the temp increase by about 3-4 times. Pressure on low and high side go up and off the gauge when this happens.

At 1500rpm, sitting still, no problem, gauge readings are like 26/240, vent temp is 40-44f and the compressor cycles regularly, even at 103 ambient..."

Hi Jeremy,

I've been putting your vehicle through different scenarios based on your statistical analysis/data that you've so thoroughly provided... very nice job! There are however, a couple of questions I'll need to ask before trying to evaluate the problem with any hope for successful analysis.

You seem to be on a level beyond the average lay persons grasp, which I do fully appreciate! So... if I ask you any seemingly silly questions, please don't take it to be from a position of any condescension... I'll still need to ask (and not assume) that nothing has been over looked in order to say that we covered ALL BASSES(!), okay?!

It would appear that you're running a very low charge of refrigerant 134A. At 100 deg-F ambient, I can't imagine why the compressor is cycling; the cycle function is a safety feature... as well as a method of controlling the evaporator temperature: Prevents the evap coil from freezing up; which would allow refrigerant to remain in the 'Liquid state' (where it should be a gas) when it enters the compressor. This is how valves get broken and the compressor's oil gets flushed out of the sump.

But when you have a substantial heatload like 90 to 100 deg-F, unless the interior of the truck is nearing 75 deg-f or below, there should be no need for the compressor to cycle except at high RPM's! So my first question is: (1) Is the cabin filter clean? Poor air flow would create a low suction pressure condition that would cause the compressor to cycle even though the ambient temp was extremely high.

In your detailed description of the trouble you said:

"At 1500rpm, sitting still, no problem, gauge readings are like 26/240, vent temp is 40-44f and the compressor cycles regularly, even at 103 ambient. I can coast down a very long hill for 30+ minutes at 15-30mph speeds with the engine in neutral, and maintain normal operation. So airflow over the condenser anywhere above idle speed from the radiator fan is enough."

I read where you said that you've cleaned the condenser, but is it possible that it needs a 'Back flow' chemical pressure wash; meaning force the dirt & grime out of the coil from behind the radiator using an actual commercial coil cleaner? I did mine at the DIY Manual car wash; you know, where there's a pressure sprayer? I didn't use any special chemicals cuz I was only there to wash the engine; first one in five years... motor was all dusty!

If you've already done all of that, we can talk about checking the S.H. (superheat)... that's just a method of finding out at exactly what point the liquid refrigerant in the evaporator is finished boiling and can not absorb any more heat during it's pass through the evap coil. If this happens too soon, then the refrigerant is not absorbing enough heat from the cabin. If this happens too late, then there is an overcharge condition which will put the compressor in danger (as described earlier in this post). Also, the evaporator will be running an excessively higher pressure/higher temperature, which will diminish the A/C system's capacity to cool the vehicle as designed.

Sorry for such a long post. You see, I do this for a living and am very aware of a few things that get overlooked ALL THE TIME, so I just wanted to be careful to cover most of the common oversights that can cause a good system not to function correctly! 'Best to you',

rig

 

[Jeremy556]

Hi Jeremy,

I've been putting your vehicle through different scenarios based on your statistical analysis/data that you've so thoroughly provided... very nice job! There are however, a couple of questions I'll need to ask before trying to evaluate the problem with any hope for successful analysis.

You seem to be on a level beyond the average lay persons grasp, which I do fully appreciate! So... if I ask you any seemingly silly questions, please don't take it to be from a position of any condescension... I'll still need to ask (and not assume) that nothing has been over looked in order to say that we covered ALL BASSES(!), okay?!

It would appear that you're running a very low charge of refrigerant 134A. At 100 deg-F ambient, I can't imagine why the compressor is cycling; the cycle function is a safety feature... as well as a method of controlling the evaporator temperature: Prevents the evap coil from freezing up; which would allow refrigerant to remain in the 'Liquid state' (where it should be a gas) when it enters the compressor. This is how valves get broken and the compressor's oil gets flushed out of the sump.

But when you have a substantial heatload like 90 to 100 deg-F, unless the interior of the truck is nearing 75 deg-f or below, there should be no need for the compressor to cycle except at high RPM's! So my first question is: (1) Is the cabin filter clean? Poor air flow would create a low suction pressure condition that would cause the compressor to cycle even though the ambient temp was extremely high.

In your detailed description of the trouble you said:



I read where you said that you've cleaned the condenser, but is it possible that it needs a 'Back flow' chemical pressure wash; meaning force the dirt & grime out of the coil from behind the radiator using an actual commercial coil cleaner? I did mine at the DIY Manual car wash; you know, where there's a pressure sprayer? I didn't use any special chemicals cuz I was only there to wash the engine; first one in five years... motor was all dusty!

If you've already done all of that, we can talk about checking the S.H. (superheat)... that's just a method of finding out at exactly what point the liquid refrigerant in the evaporator is finished boiling and can not absorb any more heat during it's pass through the evap coil. If this happens too soon, then the refrigerant is not absorbing enough heat from the cabin. If this happens too late, then there is an overcharge condition which will put the compressor in danger (as described earlier in this post). Also, the evaporator will be running an excessively higher pressure/higher temperature, which will diminish the A/C system's capacity to cool the vehicle as designed.

Sorry for such a long post. You see, I do this for a living and am very aware of a few things that get overlooked ALL THE TIME, so I just wanted to be careful to cover most of the common oversights that can cause a good system not to function correctly! 'Best to you',

rig

My refrigerant was the factory fill until beginning to troubleshoot this problem. My 2 subsequent refills have been based on measured weight of the contents of generic R134a cans I purchased at a local auto parts chain.

At 100f ambient, at idle, the compressor does not cycle - it stays on until high pressure shut off. However, at 100f and 1500rpm while still, or idle with coasting airflow, the compressor cycles off on the low end for a few seconds, before cycling back on, exactly as it does when working normally.

Understood. I work in a highly technical field with most of my time (other than useless meetings) spent troubleshooting problems that others can't solve. Most problems I work on, I have decade(s) of experience with, where refrigeration I have about 10 hours of cumulative research and experience (AKA, I don't know anything). I try to not be a typical end user and offer as many details and real data as I can.

 

[BlackWorksInc]

[MENTION=83083]rigtec[/MENTION] I'm a little confused on what you're saying? The air conditioning system on these vehicles is rather simple, they use the cycling of the compressor to maintain a consistent pressure going through the expansion valve. There's nothing else that bleeds off/controls pressure in the system except for the compressor turning, so the engaging/disengaging sounds normally unless it's cycling at odd intervals. Maybe I read your post wrong it it almost sounded like you were saying it cycling was a bad thing?
[MENTION=78273]Jeremy556[/MENTION] I know this is a stupid question, but do you know if your A/C Machine counts line volume in it's calculation? Our old R134a machine is a bit dumb and now that we threw new lines on it, we've noticed she went from about .4 lbs in the lines to about .5lbs; so when charging you have to add .5lbs to the value to account for stuff in the lines otherwise the machine will underchange the vehicle.

 

[wfo9]

This is confusing. You said pressures go up and off the gauge on low and high side when this happens.

Can you give us some readings at idle in this state compared to the 1500 RPM readings standing still (which you said induce normal cooling).

Also curious to hear how the compressor cycles at 1500rpm vs normal idle.

Sure sounds like it is airflow related at the condenser, but things are just not adding up.

The compressor cycling is just a pressure switch on the high side.... right?

The complication here is that two things happen at 1500 vs normal idle. The compressor spins faster and the fan spins faster... So is the issue the compressor or the fan. Your data point of idling down a hill with good AC seems to indicate it is airflow... but the mechanical fan is so simple. It is either spinning or not....

If I had to take a wild guess at this problem.... I would just say the efficiency of your compressor is down and it needs more RPM than it should to cool and you need a new/refurb one. That is my guess. Don't run with it just yet. LOL Seems like the fan or clutch would be more obvious and cause other issues like engine coolant temp...

 

[BLACK-FL4RUNNER]

Sounds like a bad fan clutch. They don't last forever, even the toyota ones... lol

 

[rigtec]

[MENTION=83083]rigtec[/MENTION] I'm a little confused on what you're saying? The air conditioning system on these vehicles is rather simple, they use the cycling of the compressor to maintain a consistent pressure going through the expansion valve... Maybe I read your post wrong it it almost sounded like you were saying it cycling was a bad thing?

No, I am not saying that cycling is a bad thing, depending on the IAT. The cycling is a result of a low evaporator pressure controlled by the 'Low pressure switch' located on the low pressure side of the system. This low pressure switch maintains evap pressure/temperature to prevent icing on the evaporator. But, if it's very hot out which results in a high IAT, then the low pressure switch doesn't need to cycle the compressor due to a high indoor air temp, but instead continues to run until the space temp starts to come down inside of the vehicle... that's what I was saying!

 

[JeremyB]

All your symptoms scream bad fan clutch or poor airflow. :shrug:

On a cold start, do you hear the fan start loudly and then quiet down 10-15 seconds later as the viscous fluid moves out?

Also, 200 degrees sounds a bit warm compared to my 4Runner. I've never seen it hit 200, even while towing. IRRC, it sits a bit above 180 while at idle.

 

[nevada]

When sitting still, at idle, the A/C will only cool to about 8-10f degrees below ambient temp at 100f. Vent air temperature will climb from 42 to 90 degrees f at a rate of about 1 degree per 5 seconds when set on max fan speed and non-rec, setting rec slows the temp increase by about 3-4 times. Pressure on low and high side go up and off the gauge when this happens.

At 1500rpm, sitting still, no problem, gauge readings are like 26/240, vent temp is 40-44f and the compressor cycles regularly, even at 103 ambient. I can coast down a very long hill for 30+ minutes at 15-30mph speeds with the engine in neutral, and maintain normal operation. So airflow over the condenser anywhere above idle speed from the radiator fan is enough.

These would lead me to suspect the fan clutch, however coolant temp never varies significantly (actual reading from Techstream, not the idiot gauge on the dash). I also can't stop the radiator fan when coolant temp is at operating temperature.

I have evacuated/charged and pulled vacuum between on the system twice, no change in operation or readings. It also held vacuum for over 12 hours, so no leaks.

Magnetic clutch on the compressor operates normally and all of the techstream active tests produce expected results, no stored codes.

I am pretty ignorant of cooling systems and am at a loss at this point. Hoping to avoid throwing parts at it until I find a fix, as many of these components are not cheap nor quick/easy to install.

it does sound like an air flow issue.

do you have an adjustable timing light? I wonder if it would adjust fast enough to match the fan blade speed. maybe you could test the speed of your fan, against someone else that isn't having this issue?

 

[wfo9]

All your symptoms scream bad fan clutch or poor airflow. :shrug:

On a cold start, do you hear the fan start loudly and then quiet down 10-15 seconds later as the viscous fluid moves out?

Also, 200 degrees sounds a bit warm compared to my 4Runner. I've never seen it hit 200, even while towing. IRRC, it sits a bit above 180 while at idle.

But he said he tried a stout carboard test. and the fact the issue goes away with a little more RPM. A slipping fan clutch would not improve much with Rpm IMHO.

Not saying it's not the clutch.. just does not add up to me, but I'm not an AC expert. Just using common sense.

200 does sound a tad high.

 

[Jeremy556]

Not the fan clutch. Replaced with a new OEM part and no change.

 

[Jhalko]

This thread is like listening to a bunch of rocket scientists discuss physics.


:snacker::couch2:

Sorry to go off topic Jeremy.

 

[Goldeanu5]

100% is the alternator, happened to me in the past