New AC Issues

Ac worked really well last summer. Today was around 80 and turned it on for first time. Didn’t seem to want to work so rolled down windows. Tried again on trip home and seemed to be working, but not ice cold. Was cooling things down though. Onci i got on the freeway, I notice that the air temp blowing on my hand warms about 10* for several seconds then cools down again. This repeats every minute or two until i get home.

Haven’t got a gauge on it yet, but ran it for 10 minutes in the driveway. Temps cold, but not ice cold. However NO temp variation and if anything, temps were a bit colder than they were on the freeway. Very odd, as i expect idle temps to be a bit lower than freeway. Noticed that the clutch NEVER cycled off in that 10 minutes. Very strange for 80* ambient. Wondering if this low charge or possibly a txv going or a failing thermistor. The later would imply evap freezing and I didn’t see signs of that on the driveway or on freeway. Didn’t notice any change in air volume coming from vents. On driveway, the low side lines had lots of condensation,but no ice.

the blend door seems to work very well at regulating temps in winter, do have to wonder if they have issues fully sealing the heat out when closed.
any thoughts?

 

Idle temp will be high, these truck have minimal cooling at idle.
The need the air blowing on the condenser while driving.

But it sounds like you have a different issue.

@Dm93 is the AC guy here.
I bet he can help.

 

Hard to say without seeing the high and low side pressures but is the suction line getting cold?

 

Idk about all that but I'll try.

 

Many I have worked on are like that and why I expected the freeway performance to be better than idle and I feel that I got the same or essentially worse. THat is what got me thinking that I might be I am freezing up the evap. At 80* ambient, even at idle, I expected the compressor to cycle on and off, but it just ran. That got me thinking maybe the refrigerant is low, but that doesn't really explain why it cycled on the freeway.

 

Yes, during the driveway idle test, after a few minutes I was getting a steady flow of water from the evap box discharge tube and the low side or suction line was coated with condensation. Not yet frost, but more condensation than I am used to seeing. I am used to seeing cool, but not cold enough to produce condensation. And this condensation went at least 2-3 feet from the firewall. This also had me thinking that the compressor should be cycling off (it ran the full 10 minutes) due to this and should have been giving me ice cold air out of the vents that I wasn't seeing. It was cold, but not ice cold. It is hard to think that I am undercharged when the suction line is that cold. I would have expected and undercharged condition to leave the suction line warmer, as the evaporating freon would have sucked up a whole bunch of heat in the evaporator and this line would be warm. I was always taught that the line should be beer can cold coming out of the evap. Any warmer, and the charge is too low; Any colder and the charge is too high; Idea being we want it to stay cold enough to the the whole evap coil do it's job, but not so cold that it is still freezing when it leaves the coil. I did start to then wonder if there could be a blend door issue, where the air coming off evap IS ice cold, but picking up heat from the heater core.

I will get a manifold on it today. Only issue is we will only see a high in the upper 50's today. Wished I had got this done yesterday. Did a buch of research and it appears this system relies heavilly on the thermistor to detect evap coil temp and uses this to throttle the compressor on and off vs some of the more common pressure based throttling schemes. It has me wondering if mine is failing and the incorrect reading is keeping the compressor from cycling and freezing the coil.

 

I always grab the line to feel how cold it is, the amount of condensation depends on ambient humidity levels.
Blend door actuator travel is pretty easy to check by popping out the glovebox and floor vent.

https://www.tacomaworld.com/threads/2nd-gen-information-diagnostics.784008/#post-28042158

 

Yes, I grabbed it and it was quite cold; colder than I am used to feeling at the firewall. Humidity levels were pretty low yesterday.

I added this after you probably read the last post

Did a buch of research and it appears this system relies heavilly on the thermistor to detect evap coil temp and uses this to throttle the compressor on and off vs some of the more common pressure based throttling schemes. It has me wondering if mine is failing and the incorrect reading is keeping the compressor from cycling and freezing the coil.

 

It's possible, easy enough to check. The connector is right behind the glovebox. The chart is for 09 but they are the same thru 15.

 

blend door is working correctly. I can see that the arm inside the servo maze is going all the way to the end point when the dial is at full cold. A little surprised that the next warmer setting (1 click off full cool and where you must be if you want the recirc off) is a pretty significant movement from full cold. Would like to have fresh air without the blend door opening.

 

OK, currently 54* ambient and I am getting a reading of 2.02. The chart says that 54* should be approximately 2.45 - 2.95. Clearly I am outside of the specified range and reading warmer than actual. 2.02 is middle range for ~66*. So I am reading 12* warmer than I should. Makes me wonder if this is keeping the ECU from cycling off the compressor when it should and at least a portion of the evap coil is freezing.

Do you know at what temp the ECU cycles off the compressor? I am guessing somewhere in the neighborhood of 38-40* If my error is linear, then the compressor isn't getting cycled off untill the evap coil gets to 26-28*

 

I don't know the exact temp it cuts off at, I will say most that I've watched scan data on cut off at about 34 and back on around 37-40.

I do know the voltage (measured accross the pins plugged in with the system running) it cuts off at about 1.31v and back on at 1.1v

 

So do you think that the error in the thermistor could be causing my symptoms? Would a partially freezing evap coil cause the fluctuating temps on the highway with the less than ice cold vent temps?

 

I wouldn't think so but I suppose it's possible.
The few that I have seen freeze up just basically stop blowing air because the ice blocks airflow.

I'd want to stick some gauges on it when the problem is happening and see what the pressures are doing.

I will say my truck has never blown ice cubes even when it was new and the temp does fluctuate a bit going down the highway. 40-45 degrees out of the center vent is about where it sits going down the road. 50-60 idling on a hot day.

 

ok, ambient temps in low 60's. tough to figure out what temps the evap and condensor are being exposed to for the driveway idle test, but going to guess at around 70. Nissen chart says 8-44 Low side and 180-250 on Hi side. If I use 60* ambient, the Hi side is 140-190. I got around 23 on the Low side and 130 on the high side. Air from vents probably 50* or a bit less; Using an IR, as I couldn't find my thermometer. At today's lower temps, the compressor was cycling as expected. H and L took about 5 minutes to equalize after shut down. Is that about normal for a toyota / denso TXV?

So, seems clear that I have lost some freon. put a bit of oil in schraders and detected no bubbles, so I guess some dye is going in and then the fun begins.

 

11 might have dye from the factory, I know my 14 does.
Yea those are low so your either low on charge or the TXV is stuck closed. Don't see TXVs get stuck very often.


Common leak spots include the discharge hose, condenser, and evaporator.

 

Really appreciate that tip!! Found the green dye on the condensor where the output stub is welded to the outter body. found my UV light, just couldn't find any dye. Turns out I didn't need any.

 

Quick update. warmer toady - low 70's. I clean off the old green dye in hopes of confirming a current leak vs dye from maintenance years ago. Put the gauges back on and throw in 1/3 or 1/4 can of freon I had laying around. Run for a while and vent temps a little better and now Hi side is 180-190. Run it for a while and after 15 minutes or so, the hi side is up to 230. Was thinking all of the engine heat is getting sucked into the condensor, but not sure. Shut the truck off to pull the manifold and restart to run some more and get the dye to appear. This time I put the fan on high. After a bit I go for a drive and the vent temp is nice and cold. Hmmm, no way that a 1/4 can of freon made that big of a difference. I was also experimenting with air velocity to insure there was no freezing of the evap. Notice that there is NO and I mean not a drop of water coming from the drain in the engine bay and I have been running the air for 30 minutes now. Yesterday I got a puddle under the truck and could actually feel cold air coming from the drain when I put my hand there. Any good posts discussing how to check for blockage? I couldn't identify the source of that rubber tube on the cabin side of the firewall. Any ideas on why it performed so much better today? Any chance that the txv was sticking a bit and after a good workout yesterday and today it finally decided to open some more?

Haven't gotten back out there to see if the dye reappeared yet.

Appreciate the help on this one.

 

An old trick is to use a bit of compressed air (Shop air hose) and "puff" some air up the drain hose.
If it's stopped up, you'll know it. Water will run out after you blow the clog up out of the hose.

 

It probably wasn't very low, it only holds about 21 oz.

The drain hose just turn your blower on high and put your hand in front of it, if air is coming out it's not plugged.