AC hot when asking cold?

[dsego]

Hey all, cutting to the chase.

Recently had my battery die due to a long period of no use. After restarting the LX, all seemed fine except the AC. Quite hot out these last few days, tried to ask the AC for cold, but its literally blowing hot air. As in I asked for hot instead of cold hot.

Any ideas of what this could be? Any ways to troubleshoot? I tried asking for AC codes, but they come out 00.

TIA

 

[Sandroad]

Here’s a relevant thread on that issue.

Thread 'Climate servomotor initialization PSA'

May 20, 2023

Hey y'all passing along a life changing thing I didn't know about. But apparently when disconnecting the battery you may need to re-initialize the climate servomotor(s). Last two summers I've noticed significantly less air volume coming out my vents despite a rowdy full blast fan. I initially thought I had a blend door issue but came across this utility in TIS

SO MUCH WIND coming out of the vents now. Hope this helps someone.

• tbisaacs
• Replies: 9
• Forum: 200-Series Cruisers

• 

 

[dsego]

Awesome, thanks for the pointer. Bought a cable, hopefully I can fix it soon. Will report back for historical purposes.

 

[bloc]

Awesome, thanks for the pointer. Bought a cable, hopefully I can fix it soon. Will report back for historical purposes.

Which model? The mini VCIs are notorious for having issues beyond basic diagnostics. Anything live-data or TPMS usually fails out. Vcx Nano has a good track record.

But yes please update the thread with your results.

 

[dsego]

It was a crappy model from amazon, but just ordered a VCX Nano. I'll update once I get both. Thanks y'all.

 

[dsego]

I tried the cable from amazon, and it did indeed work with the UTM image. Had to use this reddit post to get it working, but worked well.

Now, the AC servo reset does fire correctly it seems, but I still get hot air when asking cold. Any ideas?

 

[bloc]

I tried the cable from amazon, and it did indeed work with the UTM image. Had to use this reddit post to get it working, but worked well.

Now, the AC servo reset does fire correctly it seems, but I still get hot air when asking cold. Any ideas?

If you go to the live data section for the Aircon module in techstream you can see a whole lot of different lines.. like what the truck thinks the cabin temp is, whether it’s asking for different vent temps than it is producing, etc.

Poking around in there for a while would be a good place to start.

Also, is your compressor clutch engaging?

 

[dsego]

I think everything looks normal? Is there anything here that sparks interest?

 

[bloc]

If the AC is running I would expect the evap fin thermistor to be much lower than shown there.

Is your compressor engaging? Clutch on the front spinning? It should cycle on/off around 10-20 second intervals, but the exact timing depends on a lot of factors.

Either way, it should be engaging.

If you have much corrosion, refrigerant leaks at the rear AC connections above the exhaust resonator are somewhat common.

 

[dsego]

Compressor clutch relay and actual clutch working well, compressor spinning correctly when on, and not spinning when off. The regulator pressure sensor does not move at all when engaging the compressor.

Could it be that the compressor went bad? How can I check if there is no coolant leak? The pressure is at 95psi, which I would think it means no leak, but I might be wrong.

I seriously appreciate your help by the way, thank you for your responses.

 

[dsego]

Actually I take that back, it seems the pressure is increasing when turning the AC on. First pic AC off, second AC on. This tells me that the compressor is in working order?

 

[bloc]

Compressor clutch relay and actual clutch working well, compressor spinning correctly when on, and not spinning when off. The regulator pressure sensor does not move at all when engaging the compressor.

Could it be that the compressor went bad? How can I check if there is no coolant leak? The pressure is at 95psi, which I would think it means no leak, but I might be wrong.

I seriously appreciate your help by the way, thank you for your responses.

You’d check compressor health with a set of gauges. Basically when it’s engaged, is the difference between the low and high sides appropriate for the ambient temp conditions.

If you’re seeing 95psi all around with the compressor clutch engaged and spinning, yes the compressor is probably shot.

If the pressure were too low in the first place the truck should sense that and prevent the compressor running, in an attempt to protect it.. as it’s possible all the lubricant is gone along with the refrigerant.

 

[bloc]

Actually I take that back, it seems the pressure is increasing when turning the AC on. First pic AC off, second AC on. This tells me that the compressor is in working order?
View attachment 4162282View attachment 4162285

I’m not sure where they put the “regulator pressure sensor”.. you’d really need a set of AC gauges to properly diagnose the compressor.

But yes it changing pressures points to the compressor doing something.. whether that’s enough for the system to operate normally is a different question.

 

[dsego]

Definitely a leak somewhere. The weird thing is that we've added more coolant and the system does not depressurize that quick. Added a dye and will drive it around. Will report back in a week or so.