2006 LX470 – Front A/C Not Getting Cold, Rear A/C Is Cold – Error 41

[ggill310]

My 2006 LX470 is about 3 months old to me, and I’m trying to troubleshoot an A/C issue.

When I bought the truck, the A/C would not blow hot air, so I replaced the A/C blend door/servo motor. After that, the temperature control started working, but I didn’t realize there was still an issue with the cooling performance because the weather was cold at the time.

Now that I’ve been able to test it properly:

• Front A/C vent temperature: around 64–66°F, even with MAX COOL and the lowest temperature setting.
• Rear A/C: much better, around 45–50°F.
• I also fixed the front cabin temperature sensor/hose issue.
• Error 41 is still present even after replacing the servo motor.
• If I increase the temperature setting, the front vents do produce hot air, so the temperature control does appear to be functioning to some extent.
• The original refrigerant was removed and the system was recharged with approximately 2.3 lb of refrigerant, as recommended.
• I noticed the large/thick cylindrical section of the suction line near the passenger side does not get very cold when only the front A/C is running. However, it gets noticeably colder when I turn the rear A/C on. I will double-check this observation.
• With the front A/C on MAX COOL, FACE only is about 4°F warmer than FACE + FEET. This seems like a strange observation to me.

At this point, I’m wondering if I should investigate the front expansion valve/refrigerant flow. My thought is that if the suction line isn’t getting very cold when only the front A/C is operating, perhaps the front evaporator isn’t getting enough refrigerant.

 

[Super77]

Just dealt with something similar on my own 99 LC100.

Biggest gap here is you're going off vent temp alone, that can be misleading on its own. If you can get a manifold gauge set on it, the Factory Service Manual procedure (FSM AC-4) is 2,000 rpm, fan HI, recirc, full cool, doors closed, few minutes to stabilize, then read both sides. That'll tell you a lot more than vent temp about whether this is charge, airflow, or something mechanical. Vent temp is also relative to ambient - you ideally want to see a 35-40 degree differential in a well running system, maybe a little less on scorching day.

There's also a sight glass test (FSM AC-3) worth doing: 1,500 rpm, fan HI, doors open, full cool, ~5 min, then shut off and watch immediately. No bubbles at all = overcharge, brief bubbles then clear = correct charge, continuous bubbling while running = low charge. I found this test sensitive to run duration, so keep it consistent test to test.

2.3 lb is in the ballpark of my truck's dual-A/C spec (~2.2-2.5 lb), for what that's worth on a different model year. Did you recharge with r134a?

Suction line getting colder with rear A/C on is worth confirming with actual low-side pressure rather than touch. Touch is pretty subjective for this.

The FACE vs FACE+FEET difference, given your blend door history and the lingering code 41, might be a separate air-door issue rather than refrigerant. Worth not conflating the two.

I'd get pressure and sight glass data before touching the expansion valve. That'll actually tell you if front refrigerant flow is the problem instead of guessing from vent temp and touch.

 

[ggill310]

Thanks — this is really helpful. Yes, I recharged the system with R134a, approximately 2.3–2.4 lb.

I went ahead and did the manifold-gauge test following the FSM procedure: 2,000 RPM, fan HI, recirc, MAX COOL, and let the system stabilize. Ambient temperature was about 83°F.

My readings were:

Front A/C only:

• 28 low / 265 high
• 38 low / 255 high
• Later 35 low / 240 high
• Later 30 low / 235 high

Front + rear A/C:

• 36 low / 260 high
• 34 low / 260 high
• 33 low / 260 high

I also did the sight-glass test at 1,500 RPM, following the FSM procedure. I did see some bubbling initially, but it settled down, and there was no continuous bubbling that would indicate a low charge.

The pressures suggest the system is circulating refrigerant, although the high side is somewhat elevated in some of the readings.

My thinking is that the higher high-side pressure could potentially point to a weak compressor or a restriction/stuck expansion valve in the front circuit. However, since the rear A/C gets very cold, I'm inclined to rule out the compressor for now and investigate the front expansion valve/refrigerant flow more closely.

I'm also considering removing the servo motor under the passenger side and manually moving/closing the damper that controls the hot-air mix. That would at least help rule out the possibility that I'm getting unwanted warm air mixed with the cold air from the front evaporator.

The interesting part is still that the front vents are only around 64–66°F, while the rear gets around 45–50°F. That's why I'm trying to determine whether I'm dealing with a refrigeration-flow issue at the front evaporator or an air-mix/door issue.

 

[OEMGUY0720]

What’s your coolant °F temperature reading?

 

[ggill310]

Quick update — today I pulled the blend-door servo motor to address Error 41. It was a real pain to remove.

I manually moved the air flaps/dampers, and magic happened — I finally got properly cold air from the front vents, around 38–40°F!

This makes me think the main issue was air-mix/blend-door positioning, rather than the refrigerant or expansion valve. The recovery/recharge may have helped as well, and it's possible it affected refrigerant flow, but the exact moment the front A/C started getting cold was when I manually moved the damper to close off the hot-air mix.

I'm pretty sure the servo was installed in the wrong position/index when I replaced it earlier. The servo itself may be fine, but if it wasn't indexed correctly, the damper couldn't fully reach the cold position, causing warm air to mix with the cooled air.

Now I'm stuck on getting the servo properly positioned and synchronized with the damper so I can reinstall it correctly. I've been trying to figure that out, but haven't had any luck yet.

Does anybody has any pictures or repair manual on how to put the servo blend door motor back and to position the dampers back inline with motor?

Thanks all!

 

[ggill310]

Thank you so much. Error is gone and I was able to put it back with 2 screws only. 3rd one is too hard I tried one full day and gave up after my back muscles got too sore, I guess it is holding strong. Thanks all for help and guidance.