Replacing Thermistor? Pics?

[Stag_arms402]

My AC recently went out. I found out that my relay needed to be replaced so I did that. Now my compressor/clutch keeps turning on/off every 15 seconds or so. After searching the forum, I found that it is most likely the a bad Thermistor. I'd like to replace it myself as it is a cheap part & I assume easy to get to. However I have would like to know what I am looking for behind my glove box. Will I need long pliers, take something else out, or even if I'm looking at the right thing? I see a diagram online but still a little unsure. I definitely don't want to pull the wrong thing out. Does anyone have any actual pictures on how to do this? (Called a dealership & they were no help. Kept pushing ac recharge for $200)

 

[importman]

My AC recently went out. I found out that my relay needed to be replaced so I did that. Now my compressor/clutch keeps turning on/off every 15 seconds or so. After searching the forum, I found that it is most likely the a bad Thermistor. I'd like to replace it myself as it is a cheap part & I assume easy to get to. However I have would like to know what I am looking for behind my glove box. Will I need long pliers, take something else out, or even if I'm looking at the right thing? I see a diagram online but still a little unsure. I definitely don't want to pull the wrong thing out. Does anyone have any actual pictures on how to do this? (Called a dealership & they were no help. Kept pushing ac recharge for $200)

I replaced mine a while back. It's cheap but I certainly wouldn't call it easy to get to. It's easy to see but kind of hard to work with. I don't remember a lot about it but I do recall the hardest part for me was getting the old one to come out of the evaporator box. I damaged mine slightly pulling it out. The evaporator is under the center of the dash unlike older Toyotas and other brands so it's not nearly as easy to get to. It has a carrier piece that holds it inside the evaporator. I think you're supposed to be able to rotate that and it will pull out. Mine wouldn't turn so I just kept fighting with it till I got it out. Hopefully someone else will be able to add to or elaborate more on what I said. Just pull the lower cover and the glove box and look to your left and you'll see it. Good luck.

 

[CarlosV]

I thought the A/C thermistor was in front of the radiator.
Not sure if this is what you are looking for.

 

[AuSeeker]

I thought the A/C thermistor was in front of the radiator.
Not sure if this is what you are looking for.

No I have replaced that sensor you posted on mine and it is the sensor for the ambient outside air temperature that is displayed on the info screen above the AC controls.

 

[CarlosV]

No I have replaced that sensor you posted on mine and it is the sensor for the ambient outside air temperature that is displayed on the info screen above the AC controls.

Thanks AuSeeker. Sorry wrong info

 

[AceSpades]

Does your info screen display the correct outside temperature? If not, this may well also cause the AC to stop functioning. If it has failed it will think it is too cold outside and wont let the AC engage. Common on BMW 3-series, i shorted the temp switch to fool it to think it was full hot (120°) outside instead, and the AC started working... But if your info display reads outside temp correctly, then proceed with the evap thermistor

 

[importman]

Does your info screen display the correct outside temperature? If not, this may well also cause the AC to stop functioning. If it has failed it will think it is too cold outside and wont let the AC engage. Common on BMW 3-series, i shorted the temp switch to fool it to think it was full hot (120°) outside instead, and the AC started working... But if your info display reads outside temp correctly, then proceed with the evap thermistor

I'm not the OP but I'm pretty sure he's on the right track. That thermistor in the evaporator is a known pattern failure. I had the same symptom on mine and replacing the thermistor corrected it. There are threads on here that discuss it at length along with some very good tips on changing it.

 

[AuSeeker]

Does your info screen display the correct outside temperature? If not, this may well also cause the AC to stop functioning. If it has failed it will think it is too cold outside and wont let the AC engage. Common on BMW 3-series, i shorted the temp switch to fool it to think it was full hot (120°) outside instead, and the AC started working... But if your info display reads outside temp correctly, then proceed with the evap thermistor

I don't think that applies to our 4th Gens T4Rs, I say this because even though as I posted above I replaced the outside air sensor in my 2004 Limited and the outside air temperature still doesn't display on my readout and my AC and heater works very well/perfectly.

 

[averyislost]

Anybody able to remove the thermistor without damaging the carrier on a 03-05? I've seen the pics of it, as well as looked at it myself. But I'm nervous to damage it trying to remove it due to all the previous reports of other people doing the same.

Looks like mine may be incorrectly mounted and/or damaged after getting my evaporator replaced last year. My compressor is short-cycling causing my AC to blow lukewarm (lukecold?) for a few seconds before cooling down again. When I unplugged the thermistor and jumped the connection, the compressor would remain on and I'd get temps around 8-10 degrees colder than I was before. Looks like it needs to be either replaced or repositioned. Thanks!

 

[Drcoffee]

I think you might be going in the wrong direction. If that part was fautly you would not get any cycling at all.

You need to make sure your refrigerant is up to the correct level. It might be cycling on and off because its low and drops pressure once it runs out of refrigerant. Use the sight glass up front and see how it reads.

 

[averyislost]

I think you might be going in the wrong direction. If that part was fautly you would not get any cycling at all.

You need to make sure your refrigerant is up to the correct level. It might be cycling on and off because its low and drops pressure once it runs out of refrigerant. Use the sight glass up front and see how it reads.

Thank you for the reply!

Unfortunately, I had both my local shop I trust, as well as the dealership check my levels last year. My truck was doing the same thing last year but summer temps weren't quite as high where I am as they are this year. Not to say I couldn't have them checked again though, you might be right.

The sight glass test looks to be correct. I had my girlfriend shut off the AC and it looked to bubble (foam?) and run clear quickly, and I'm not getting any bubbles when it's running. but you can see the refrigerant flowing. I had the shop add a UV dye as well so it was easier to check with the UV light.

Wouldn't the test I did with the jumper point to that being a possible issue, or would that not be the case? I am wondering if maybe when I had my evaporator replaced the thermistor may have been moved slightly and not be in the correct position as it was stock.

I will say, before the evap was diagnosed to be leaking and I had it replaced, and I had low refrigerant, the issue seemed to be similar. But it would never get as cold as it does now. It would cool a bit and then run lukewarm when the compressor cycled off. Now it runs "cold" but the compressor seems to cycle too much and not run cold when it cycles off.

 

[rpm50999]

yes - thermistor troubles

I have been having the same problem with my 07 4th gen for years and was constantly being misled with refrigerant level posts. This sensor does NOT always just fail. It seems that a lot of the time it skews resistance up making it appear to the controller that the evap is colder than it is. I'm not sure if jumping it forces it on or causes the controller to assume it is faulty and shutdown, but there is a chart in the service manual that shows the resistance it should be at. I'm going to make a new post and show all the details of my diagnosis and repair, I figure I owe it to the others here that have been very helpful.

 

[averyislost]

I have been having the same problem with my 07 4th gen for years and was constantly being misled with refrigerant level posts. This sensor does NOT always just fail. It seems that a lot of the time it skews resistance up making it appear to the controller that the evap is colder than it is. I'm not sure if jumping it forces it on or causes the controller to assume it is faulty and shutdown, but there is a chart in the service manual that shows the resistance it should be at. I'm going to make a new post and show all the details of my diagnosis and repair, I figure I owe it to the others here that have been very helpful.

Good luck, I ended up replacing mine with a factory new thermistor, and it didn't change a thing. You will break the black plastic "carrier" piece that the thermistor sits on that goes into the heater core housing. I ended up buying an entire used ac/heater core housing just to get that one little piece and see how it worked. With the piece broken it will still stay in the heater core housing, but it wasn't very tight for mine.

I had no changes after replacing the thermistor with a fresh OEM one from the dealer. Minimal changes if I rotated it around (clocked it on the carrier it sits on). Make sure to figure out how it sits on the carrier before removing it (take pictures), it's hard to get it back on the perfect spot on the carrier like factory.

The only time I could get my AC freezing cold was disconnecting the thermistor and jumping those wires. I honestly think it's just how the AC system is designed in this thing.

 

[rpm5099]

I got it fixed, went a different route. See post I made here:

A/C Cycling between Hot and sort of Cold - Thermistor problem? - Read this before rem

Good luck, I ended up replacing mine with a factory new thermistor, and it didn't change a thing. You will break the black plastic "carrier" piece that the thermistor sits on that goes into the heater core housing. I ended up buying an entire used ac/heater core housing just to get that one little piece and see how it worked. With the piece broken it will still stay in the heater core housing, but it wasn't very tight for mine.

I had no changes after replacing the thermistor with a fresh OEM one from the dealer. Minimal changes if I rotated it around (clocked it on the carrier it sits on). Make sure to figure out how it sits on the carrier before removing it (take pictures), it's hard to get it back on the perfect spot on the carrier like factory.

The only time I could get my AC freezing cold was disconnecting the thermistor and jumping those wires. I honestly think it's just how the AC system is designed in this thing.