Climate control temp sensor

[Muddy Bean]

My auto climate control is very cold when set at anything other than 85 which is the max heat setting. Basically, set at 85 it's full on and gets super hot in the cab. When set at just one or two notches below 85, it's cold. Blender door seems extreme. This is the case when using controls manually or automatically. 1998 100 series. Is this an issue with the interior temp sensor? I looked at the exterior one and it looks fine.

 

[OregonLC]

There's a 3/4" corrugated plastic hose that connects to a port by the driver's right knee. The system draws in cabin air from this to sense temp. Check to see if it's either blocked or if the hose has come off.

 

[Muddy Bean]

There's a 3/4" corrugated plastic hose that connects to a port by the driver's right knee. The system draws in cabin air from this to sense temp. Check to see if it's either blocked or if the hose has come off.

So I looked for this but never found it. Here's a pic of the heater floor vent area:

 

[OregonLC]

This is what you're looking for. Hose attaches to back side.

 

[Layonnn]

This is the case when using controls manually or automatically. 1998 100 series. Is this an issue with the interior temp sensor? I looked at the exterior one and it looks fine.

If its the same issue using the temp controls manually, (not auto), then i would not suspect it to be the temp sensor.

If your AC selector is set to off, so you are just running the vent fan (with the engine at normal operating temps), if you set the temp to all the way hot with the fan speed at medium, if you slowly back down the temperature is there a gradual change, or does it blow ambient temp air as soon as you decrease the temperature?

This is what you're looking for. Hose attaches to back side.

So thats what that opening is for, hmm. Thanks.

 

[Muddy Bean]

This is what you're looking for. Hose attaches to back side.

Thanks! Now I know. Checking this today. I'll post back.

As to the question. A/C button is always off. Unless I defrost. But I rarely do. Set fan speed to medium. Set heat to 85. If I turn the temperature knob down just two clicks to what I assume is 80 it blows out ambient air (which is very cold in my case. Was 15 last night). If I leave it at 85 it gets super toasty toasty in there. So what I typically do is turn it to 85. Leave the fan speed on lowest setting. An when I get hot, I back It off a notch or two on the temp setting. Then it gets nippy and I'll click up a click or two back to 85....until it gets too hot. On a long drive, it's unbelievably annoying. Now imagine traveling with your wife or other peeps in the truck. It was super annoying this past week if with four of us in there. On my old Camry with manual controls, I could set the temp to something somewhere in the middle of the red and blue temp control and it would blow out comfortable air for hours with just a rare input from me.

EDIT: To answer your question, it's not a gradual temp change. The air begins to blow cold within 60 seconds.

 

[2000UZJ]

This is what you're looking for. Hose attaches to back side.

I've always wondered what this blank socket was for, thanks for the info.

 

[APKhaos]

While you are in there, clean the temp sensor itself with MAF cleaner or similar [I used 1:1 IPA:Water] and a soft paint brush. Mine was caked with dust and general frass. The hose was attached, but cleaning the sensor straightened out the heater operation.

 

[Muddy Bean]

While you are in there, clean the temp sensor itself with MAF cleaner or similar [I used 1:1 IPA:Water] and a soft paint brush. Mine was caked with dust and general frass. The hose was attached, but cleaning the sensor straightened out the heater operation.

And mucho thanks to you guys. Took it apart:

1. Yes, the corrugated hose was indeed disconnected and just lying there.

2. The temp sensor was dirty with dust.

Cleaned it with some rubbing alcohol and q-tips, and reconnected the corrugated hose. And viola! Problem solved. Thanks again. Here are some pics:

 

[drmwvr]

Great info in this thread! Will file away for future use!

 

[2000UZJ]

Now that I look at it, mine has fallen off as well. My AC works fine. I always thought that hose was a drain for something. I thought it was a strange place for a drainage line lol.

 

[APKhaos]

That was about what mine looked like.

12 years of dust and frass on the temp sensor completely disabled the heater. Spent all last winter chasing possible air mixer door servo problems, and it was this little bugger the whole time! Yours is nicely cleaned up and shiny just like mine, and the heat is a great payoff for this simple fix.

 

[pwcummings]

First one to get K&N to engineer a high performance filter for this gets a mud sticker ;-/

 

[Muddy Bean]

First one to get K&N to engineer a high performance filter for this gets a mud sticker ;-/

nice. honestly, it was pretty easy to get to. And it has 100,000 miles and 15 years of dust and it still wasn't as bad as it could have been. But, a little door/hinge on that slotted section of the knee panel would be nice. Just flip the little door open, spray some compressed air, and you're done.

 

[Warrenpfo]

Thanks, this should go in the 100 tech section as a sticky

 

[bamabrock]

Good info. Bookmarked this thread to the "interior" folder

 

[Muddy Bean]

Just finished a 600 mile trip yesterday. Really loved having a working auto climate control. Thanks again you guys for the hints on this.

 

[00N8]

I'm going to have to check this. Great photos!

Sent from my iPad using IH8MUD

 

[Spanktron9]

Just returned from a 5 day trip to Eastern Oregon with the GF and great dane. I had the opposite problem as the OP. Anything but set to absolute cold resulted in disco inferno in the cab. My solution was much like his, set it to a couple notches up, and when the heat becomes too much, dial it down and get 19 degree ambient air into the cabin. Annoying but functional. (I would have bitched more, but at a gas station saw a guy traveling in a POS pontiac with the driver's door duct taped on, and no driver's window. He had a face mask on to combat the sub-freezing winds. Looks like he had his whole world in the back seat. Gave me some perspective.)

Anyway, thanks for the great info. Off to do some cleaning and check the hose connection. Hopeful that this is my issue as well. Likely since I just bought the rig and it has 250K on it.

 

[Spanktron9]

Done. Total 1 job. My sensor was only slightly dusty, but both the hose AND the electrical connection were disconnected. Hooked it back up and it appears to be all good. Thanks to everyone for the info and pics.