drwhosc

So looking at my front drivers fender, I did not have an alternator hose. Not a biggie, got a replacement from rodger. BUT no outside air temp sensor. Looked for a replacement, and it is turning out to be a biggie.

Are there any other sensors I can use besides a new one from porsche... Will a BMW, Mercedes or volvo model work. Those sensors are about 10% of what Porsche wants. I saw some resistance values posted here, and will contininue to search for a replacement based on those, But I am hoping to tap into the collective knowledge...

WallyP

If you like to tinker, you might consider checking the electronic parts places for a thermistor that comes close to the specs. Then start measuring cans to find one that fits the hose...

drwhosc

wally I did find your HVAC guide, and it is awesome. Good overview of the system. thanks for posting that.

I also found this thread https://rennlist.com/forums/928-foru...mp-sensor.html that is what I am looking for. I just hate the fact that we are stuck with little alternatives in this area. the guts of the part is so inexpensive, and Porsche now wants $300 for a tin can with a $3 part. It would be good to have a DIY alternative.

StratfordShark

If you do try a 220 ohm thermistor, make sure it has correct coefficient. They come as negative temp coefficient (NTC) where resistance decreases as temp increases, and PTC where resistance rises with temperature.

I know that in the HVAC system you get max heat when the resistance if sensors + slider is at high end of spec, so I am pretty sure you need an NTC thermistor, but maybe someone else who had substituted components can confirm.

drwhosc

Yes on the NPT these were the numbers I found. I also saw another post that measured the resistance that I wanted to confirm. And then there was a mention of some values in the WSM, but I have not found those yet. Also these things are dialed in at 25*C, so 77*F is the value I am looking for.

1000 ohms at 32 F
600 ohms at 68 F
500 ohms at 85 F

Thanks

drwhosc

Looks doable... https://rennlist.com/forums/928-foru...tor-value.html

Will still look for a used one, but the budget is not happy...

murray928

Followed up on Mrmerlin's post of 07-11-2010. The link was dead but I followed through on the Newark website searching for the part number of the thermistor he used. It has been superceded but the new part would seem to fulfil the function. Here is the link:
http://www.newark.com/honeywell-s-c-...&rpsku=30F1765