gtroth

I'm dealing with a squeaky right side blower motor, and with it opened up I see what I guess is a temp sensor flopping around in the duct nearby. What is this supposed to look like?

nine9six

Its difficult to see the picture clearly, but...
Is there a hole in the casing where just the rubber base of the sensor should plug into, and only the sensor stalk should protrude into the chamber?
If not, then I guess this is how Porsche engineered this?

ToreB

Here's pictures of how the sensor should look like.
Cheers,
Tore

Paul M

I think that's the sensor that fits between the fins of the evaporator core, not one of the two that have the twist connection into the top of the airbox that are shown in Tore's photo.

Edit: If I remember correctly, it should just slide into an opening on top of the airbox, under the left side of the expansion valve.

ToreB

Paul, you are probably right, it is the connector lead to the evaporator sensor.
Cheers,
Tore

gtroth

Thanks, fellas. Sorry about the lousy pic.
Starting at the top of the pic above, two white wires go through a hole and are connected under shrink wrap to a black cable that is part of the silver rod (sensor) that is rattling around I the duct. The sensor has a barbed grommet where it meets it's cable - looks like it mounts in a hole.

So I should look for the correct hole for this, heh? Why would someone make this change?

Here's an equally lousy pic of the routing of that white wire:

gtroth

Update- this sensor ultimately failed and prevented the compressor from starting. I measured an open circuit between pins G22 and G18 on the CCU harness, so I soldered in a 3.3K resistor in place of this nonsense (telling the CCU the sensor is reading 20deg C) and now have ice cold air.

I'm not detecting an evaporator freeze, of course, but I have never been since buying this car 7 years ago. What should I be worried about if the evaporator freezes?

nine9six

Is the sensor not sold separetly and this is the reason for soldering in a resister, as opposed to replacing the sensor?
Just curious?

gtroth

Access to the evaporator where the sensor belongs is very difficult (remove gas tank, etc.).

ToreB

The evap freeze sensor is very important for the A/C operation. It is the only mechanism that shuts off the compressor in normal operation. (runs in 5-10sec intervals in 20 deg C ambient)
I have not seen any ice buildup damages on the evap, but guess this could damage the air box as well as the evaporator itself.
Cheers,
Tore

Vandit

Look at this pic.



You see toward the center of the HVAC assembly, there's the silver piece with two ports? That's the expansion valve and it is attached to the ports on the evaporator. That's just FYI, but if you look toward the left of that piece, you see a rubber grommet. That's where the evaporator temp probe goes. That placement puts it in the fins of the evaporator.

Better pic.

Paul M

Couple more pics with the expansion valve and hoses still in place, final one looking from above with hoses disconnected.

gtroth

Ah, ok, so it looks like I can replace the sensor pretty easily from the top without any disassembly, is that right?

Paul M

Yep. If you shine a light in there you should be able to see the fins of the evaporator.

gtroth

I'll replace the sensor ($88.75), but I guess I'd like to understand this better.

Does it do more than detect a fault condition (an evaporator freeze)?

For for the last 7 years and who knows how long before that, this sensor was measuring the wrong thing (duct air temperature), so if there were any freezes, the compressor was never shut down because of it.

But since I put in the temporary 3.3K fixed resistor, I don't believe the air temp has ever been this cold. Hurts my hands when it's 95F outside. I never added any refrigerant (or done any other fixes), though I did measure it and was nominal.

Maybe you can shed some light on what may be happening here?

Many thanks!