[thescot14]

Hey guys, first time question. I took my 2005 Toyota Sienna into the local trusted mechanic and got a high quote to fix my ac. They determined that the evaporator temperature sensor is faulty and said that the only way to get to it is to remove the dash. Anyone out there that can point me in the right direction to where this part is located? I am going to do the work myself, and want to remove as few parts as possible to do it.

 

[sixto]

I don’t know about these Siennas specifically but it makes no sense that the front evap temp sensor can’t be replaced by reaching under the dash.

Sixto
‘04 LE FWD 197K miles

 

[paul r]

It could be this part. Not sure, ok?
88625.

 

[paul r]

Post number 16 and 19. for ideas. It is quite a job. If you do it please post back. Cheers

2006 Limited anybody replaced front AC Evap.

Dye indicates a very slight front AC evaporator leak. My fair priced and reliable independent shop is having trouble finding an OEM evaporator without a whole assembly attached to it at over $1500 part only. Plus 9 hours shop time to r&r most of the dash. Several non-oem evaps available but...

www.siennachat.com

 

[thescot14]

It could be this part. Not sure, ok?
88625.

Yes, from what I have seen online that is the part. Any additional images about where this is located relative to the glove box?

 

[paul r]

I wish I could say where it is located but let me ask you this. What is happening to the ac system? You are the first with this problem that I know of since I have been on this 2ng gen forum

 

[thescot14]

I wish I could say where it is located but let me ask you this. What is happening to the ac system? You are the first with this problem that I know of since I have been on this 2ng gen forum

Great question. Currently the AC runs cold, but it cycles in and out. When it starts to run warmer I can still tell the AC is running by feel (air does not feel humid) then cycles back to cold again. This happens randomly and does not appear to be repeatable with anything I do. I am not sure how a tech would determine that this is the issue. His notes do state that the ac system otherwise was running well with good pressures.

 

[paul r]

Next time on the road while the system is on and cooling report back what the temperatures out of the drivers side and passenger side vents feel like . I'm talking about the vents by the radio. Is one warmer/cooler than the other? Which, if so?
By the way , what level trim ? CE , LE, XLE?

 

[jseyfert3]

The sensor is of course on the evaporator coil, which is buried inside the front air conditioner assembly: Toyota Sienna Service Manual: Disassembly - Air conditioning unit - Air conditioning

To get that? Well...

Hey guys, first time question. I took my 2005 Toyota Sienna into the local trusted mechanic and got a high quote to fix my ac. They determined that the evaporator temperature sensor is faulty and said that the only way to get to it is to remove the dash. Anyone out there that can point me in the right direction to where this part is located? I am going to do the work myself, and want to remove as few parts as possible to do it.

It's not just removing the dash. It's removing the windshield wipers, windshield cowl (my initial browsing shows this to already be a couple hours both ways, cause it has to come out for the spark plugs which I'm planning). Then you have to remove the dash. Including the passenger air bag assembly, intermediate steering shaft, transmission shift cable...well, everything. You are not just removing the dashboard. You are utterly and completely tearing the entire inside front of your vehicle apart. Oh, and not to mention, you need to remove the refrigerant first, since you're breaking AC lines, and so you'll need a new dryer for your AC system, and you'll either need a vacuum pump or have a shop evacuate and fill the AC system afterwards. Whatever you do, be absolutely sure that the AC system is leak checked and 100% leak free once the unit is back in place before you start piecing your dash back together... Toyota Sienna Service Manual: Removal - Air conditioning unit - Air conditioning

I hope I'm wrong, and there's a way to get this that bypasses all this. But looking at where it is...it seems doubtful. And if you need to do what the above service manual links are saying, well. I try to do a lot of my own maintenance. I just swapped my water pump. I don't think I'd do this. I'd live without AC or I'd get a small loan if needed to pay someone to do this. I mean maybe, if I wasn't too busy with other things and the weather allowed me riding my motorcycle for a month. If you choose to do this, I wish you luck. While you're at it, may swap the expansion valve as a PM cause you're pulling it anyway, and do your spark plugs since you've removed the windshield cowling. And make damn sure you've done all the testing you can possibly do to rule out the possibility that it's anything easier to access than that sensor is!

My final tip: I personally like having the factory service manual when I'm doing things. One particular 2nd gen model FSM is what the above links to tsienna.net are to. But it doesn't hurt to pay $20 to get a two day subscription to the real thing in case there's anything different for your particular model. Especially with something that will involve such huge amounts of time and effort as this does. https://techinfo.toyota.com/

 

[jseyfert3]

How much was the quote to fix this? And I'd check with them on how exactly they determined it's the sensor before they start, if you go with them.

You can look at the actual evaporator temp sensor info with the Intelligent Sensor, which I unfortunately do not have (at least yet). If that temp sensor info is giving wacky temps, then yeah it's probably bad, or at least the wiring to it is. But the only way to know for sure is to pull the sensor and check it directly. That's outlined here: Toyota Sienna Service Manual: Evaporator temperature sensor - Air conditioning

 

[3Wheelerguy]

The sensor is located on the evap core itself. It is NOT on the firewall. That is the expansion valve.

The sensor in question turns off the AC if the core temp gets to around 33F degrees to prevent freezing of the core. In ALL my years I have never replaced one. I could be wrong but I think it was misdiagnosed.

 

[sixto]

Yes, the probe extends into the evaporator core but I’m 99.44% sure the sensor is accessible without splitting the air handler.

Here’s a picture from the passenger footwell of our ‘04 LE with basic AC after removing the inner kick panel. Hold the outer ring of the clip while turning the center counterclockwise with a Philips screwdriver. Once the head lifts the slightest bit, you can pull off the panel sending the clip flying.

The yellow and green wires go into a connector off screen then emerge as black wires in the blue sheath. They go into the evaporator housing through that u-shaped thingy that conveniently fits in a 10mm spanner/open wrench. The scuff marks are from the wrench slipping but it seems a counterclockwise turn releases the sensor. I’d have to see a replacement sensor to guess how it’s held.

Sixto
‘04 LE FWD 198K miles

 

[BillG]

I always thought cycling A/C like this was either a slipping belt or a failing A/C clutch? An additional thought is, do you happen to have a loaded van with the digital temperature controls? Lastly, is it possible that maybe one of the common failure points (i.e. blend door servo) is the cause? It's not that ultra-rare failures don't happen in a 17 year-old van, but I think I'd actually take the van to a Toyota dealer and have them investigate the problem (without telling them the proposed solution) and see what they come up with.

 

[thescot14]

How much was the quote to fix this? And I'd check with them on how exactly they determined it's the sensor before they start, if you go with them.

You can look at the actual evaporator temp sensor info with the Intelligent Sensor, which I unfortunately do not have (at least yet). If that temp sensor info is giving wacky temps, then yeah it's probably bad, or at least the wiring to it is. But the only way to know for sure is to pull the sensor and check it directly. That's outlined here: Toyota Sienna Service Manual: Evaporator temperature sensor - Air conditioning

So I just called them to learn a little more about how they know that this is the failure, and the tech explained that after checking everything else related to the ac, he was able to "wiggle" or somehow move the part in question and the system returned to normal when he did. So to be clear they are saying the failure is either the sensor, pigtails going to it, the plug, etc. They only way they feel confident is to pull the entire evaporator which is why the price tag is so high.

 

[floridanative]

When it happens, how long does it stay warm for? My AC will slightly warm up every so often, especially noticeable when it’s really hot and humid out, but it only lasts a minute or two and then is right back to ice cold. I think this is normal and part of a “defrost” cycle to keep the AC from icing up.

-Mike

 

[bencahill]

When it happens, how long does it stay warm for? My AC will slightly warm up every so often, especially noticeable when it’s really hot and humid out, but it only lasts a minute or two and then is right back to ice cold. I think this is normal and part of a “defrost” cycle to keep the AC from icing up.

-Mike

Ah, I noticed this recently and wondered what it was. I also noticed the engine ran at lower than normal RPMs (around 500 I think) during the same period of time. (I was parked, idling, hot engine, hot day.) That would make sense.

 

[thescot14]

Yes, the probe extends into the evaporator core but I’m 99.44% sure the sensor is accessible without splitting the air handler.

Here’s a picture from the passenger footwell of our ‘04 LE with basic AC after removing the inner kick panel. Hold the outer ring of the clip while turning the center counterclockwise with a Philips screwdriver. Once the head lifts the slightest bit, you can pull off the panel sending the clip flying.

View attachment 57464

The yellow and green wires go into a connector off screen then emerge as black wires in the blue sheath. They go into the evaporator housing through that u-shaped thingy that conveniently fits in a 10mm spanner/open wrench. The scuff marks are from the wrench slipping but it seems a counterclockwise turn releases the sensor. I’d have to see a replacement sensor to guess how it’s held.

Sixto
‘04 LE FWD 198K miles

Paul,

This is exactly what I was looking for! They said they were able to wiggle the wire and eliminate the issue, so having easy access to this makes complete sense. I have not tired to do the counterclockwise turn yet, today I was gathering more data. I can say at least that for whatever reason the issue is not presenting itself as obviously right now. I tried wiggling and pulling on the wires myself with the car on, but could not create a direct correlation. If I can replace the part as easily as turning this counterclockwise I think I will just order the part and do it, its $16.

 

[thescot14]

Next time on the road while the system is on and cooling report back what the temperatures out of the drivers side and passenger side vents feel like . I'm talking about the vents by the radio. Is one warmer/cooler than the other? Which, if so?
By the way , what level trim ? CE , LE, XLE?

Paul,

With your question and some time during lunch today I hooked up 4 thermocouples to all the vents on the dash (driver left and right, passenger left and right) and plotted the data for about 30 min. No major failure was noticed while I was driving but I did notice smaller fluctuations. You can see in the plot below that during these smaller fluctuation whatever it was affected all the vents. To have something to compare it against I did unplug the sensor around 8-9 min into the test, then plug it back in. That is the major spike in the middle.

The pattern of failure times is very cyclical, every 30-40 seconds. It is as if the ac seems to fail but before it becomes more noticeable it recovers. I did try and wiggle the wires but cannot remember exactly when so its hard to attribute any small change to that. I will do a better job next time correlating the time when I am doing something different.

 

[thescot14]

When it happens, how long does it stay warm for? My AC will slightly warm up every so often, especially noticeable when it’s really hot and humid out, but it only lasts a minute or two and then is right back to ice cold. I think this is normal and part of a “defrost” cycle to keep the AC from icing up.

-Mike

Mike,

I am really not sure, you might be right. I just posted some data so you can see how often this happens. I have been in plenty of cars that never have these fluctuations, so I am thinking that something is wrong. These small fluctuations are also not the main issue I am dealing with. There have been other times where the AC stopped blowing cold for hours.

 

[thescot14]

I always thought cycling A/C like this was either a slipping belt or a failing A/C clutch? An additional thought is, do you happen to have a loaded van with the digital temperature controls? Lastly, is it possible that maybe one of the common failure points (i.e. blend door servo) is the cause? It's not that ultra-rare failures don't happen in a 17 year-old van, but I think I'd actually take the van to a Toyota dealer and have them investigate the problem (without telling them the proposed solution) and see what they come up with.

We are driving around without it being loaded up, and this is happening. The belt door is also a thought I have had. I had to replace one already (the one that is accessible from the driver side). I believe there is another blend door that is accessible from the passenger side, but I have not replaced that one yet. Do you know what the passenger side blend door does? The driverside if memory serves changed the mode of the van's ac (blowing at feet, or face, or both) does the passenger side combine warm and cold air when the car is set to anything other than HI or LOW?