Caloric Feeler

[hardwick63]

Has anybody found a cheap way of replacing the Caloric Feeler temp sensor??

[Oh Haha]

got a pic of what you are talking about?

That's a nice 993 you have the garage, BTW.

[hardwick63]

Please check *********** site below for the sensor.

Porsche 911 Heating Parts

[Oh Haha]

My apologies to you. I thought you were a spammer.



I did some investigation and know what you mean now. I searched the Pelican catalog but did not find it anywhere. (The site in your link shows it as unavailable).

These are what you are talking about:

[Oh Haha]

[hardwick63]

Yep thats it although there is only one, check previous forum entry below for exact explaination of the sensor, thanks for the comment on my car, I thought 993 were from the 90s, mine is a 1982


Autoheat problem

[Oh Haha]

Um, yeah about the 993 comment-I thought I would catch you in a lie because I know the car in the garage is an SC.
We've been hammered by spammers the last 24 hours.

As far as the problem at hand-
I would try a Porsche dismantler and see if they have one. AFAIK, the part itself is spot-welded into the heater tube. You could easily attach with some sheetmetal screws.

I would believe the wires run up into the cabin to the floor console. You may have to splice the new one in.

[hardwick63]

Thanks for your help, the problem with used parts is knowing whether they work.
Do you or anybody else know of a replacement part that can be brought from one of the electronics companies that might be suitable, this must be a common fault with this age 911.

[Hodgey]

Off topic slightly but are you any where near Trevose?????

Neil

[Oh Haha]

Sorry, I don't know of a solution for this. Good luck with it and please post any new info you may find.

I'm debating on going to manual heat in the future.

[hardwick63]

Hodgey, Trevose is further up the coast from me, I live in Porthtowan, between St Agnes amd Portreath.
I don't want to give up on the autoheat system quite yet, any help with the sensor will be greatly received.
Thanks

[Oh Haha]

bump for others to see and chime in.

[hardwick63]

Bump

[hardwick63]

Fixed, if anyone wants to know how you can fix the sensor for £10, let me know.
Special thanks to Brian Haggard for his help in fixing my autoheat.

[wallet]

HI hardwick64 could you give me the fix foe the temp sensor Please?

[hardwick63]

Brian Haggards Fix for the Caloric Feeler
The “caloric feeler” is an NTC thermistor whose resistance varies inversely with temperature. The factory manual says it should read about 135 ohms on a warm engine (212 F.) This is a “J series” in the parlance of the family of R-T curves for thermistors. DigiKey part no KC005G-ND meets this curve and is the one I used to replace the thermistor in the OEM housing that is riveted to the air duct connector between the left heat exchanger and its flapper box.

Digi-Key - KC005G-ND (Manufacturer - AL03006-1576-101-G1)

In the picture on DigiKey, it looks really big. The thermistor itself is actually 1/8” long …

To replace the thermistor, remove the air duct connector with the thermistor housing attached. Then test the resistance of the installed unit by measuring the resistance across the end of the wire that is connected to the autoheat control between the seats. Measure at whatever the ambient temperature is, then heat it with a cigarette lighter and see if the resistance changes. Exact is not necessary -- if the resistance is in the ballpark, don’t replace it -- the factory says replace it if it is “way off.”

To continue, cut the wires to the thermistor, near the thermistor (leave as much of the existing insulated wire as possible.) Drill out the rivets and remove the thermistor housing.

Mount the thermistor housing in a vice or other device. Measure the inside diameter of the cylinder that holds the OEM thermistor. Using a drill a couple of sizes smaller than that diameter, drill down the centerline of the cylinder, removing the material that holds the thermistor in place. (You’re not trying to save the thermistor – just removing the material inside the cylinder.)

The material is quite hard and you will wear out the outer corners of the drill’s twist. You may have to sacrifice it to the cause and use a new one. Drill again with a larger size drill to remove all but about 1/16” of material inside the cylinder so that none of the cylinder’s metal is exposes.

Get a tube of SENSOR SAFE silicone sealant.

Now get everything under the car.

Strip about1/2” of insulation from the OEM wires left under the car after you cut the original thermistor wires. Slip heatshrink on both wires – about 1-2” each –DO NOT shrink them yet.

Bend the leads on the new thermistor into a “U” with sides parallel and perhaps 1/4” apart. About 1/4” and 1/2” from the thermistor, twist loops into both leads (4 loops total.) For each lead, feed one stripped OEM wire thru the loop farther from the thermistor and double it back on itself. Solder the connection between the copper OEM wire and the thermistor lead. Cut off excess thermistor leads. Slip the heatshrink over the soldered joint and shrink it into place – do not cover the loops closest to the thermistor.

Slide the thermistor into the cylinder so that only the thermistor protrudes past the end of the cylinder—and will be in the airstream coming out of the heat exchanger. Fill the cylinder with the silicone, keeping the length of exposed leads from touching either each other. Fill the cylinder from end to end and let it set up. The loops in each lead are now buried in the silicone and will secure the thermistor.

Reinstall the thermistor housing with steel poprivets. Put it all back together and test your heat.

Let me know how your's turns out.

This worked for me.
Colin

[wallet]

Thanks Colin i have been trying to source an alternative but the choice of ntc thermisters is mind blowing.
thanks again i will let you know if i get some heat (my sensor measures 20 mohms)
clive.

[wallet]

hi Colin i have sorted the heating thanks for your help.
clive

[rokemester]

Thanks to Brian for this clever fix. Here are a few pics of my attempt. Hopefully it will help a few others out. I know they don't look that great, but I'm getting the proper resistance reading.


Here's a shot of the original thermistor before drilling out.


The flapper box was a bugger to get out. Stripped two of the studs. The boxes look kind of crappy and corroded but they are really made of substantial metal, very solid. You may not need to drill out the rivets on the sensor holder. The sensor tube has indents which are compression fit.


Before fitting into the sensor tube


Used sensor safe, heat resistant (over 600 degrees F) silicone, Permatex


You can see how the thermistor is oriented in the sensor tube.

I'm now waiting for another heat controller console as I suspect the circuit board in my 87 911 is buggered.

[rokemester]

Also decided to add spade connectors so if I need to replace the thermistor again, I won't lose any more of my original OEM wire to the controller.