Pelican Parts Forums - Oil temp gauge reading when cold

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- - Oil temp gauge reading when cold (http://forums.pelicanparts.com/porsche-911-technical-forum/1127970-oil-temp-gauge-reading-when-cold.html)

Fwiw, those temp sensors, if VDO, have quite a large margin of error, something like +/- 15%. I know as mine was way off and I had to reset the calibration table in my Megasquirt. Obviously you can’t do that but you should be able to test it to determine if/how much it’s off

Here’s the calibration chart. Test your out before you start playing with the gauge.

https://uploads.tapatalk-cdn.com/202...2610aca1cc.jpg

Quote:

Originally Posted by SCadaddle (Post 11820403)

That was me. SmileWavy

Yeh, good catch! That was a real Homer "Doh!" moment when I read that :D

I'd happily have given you credit, but couldn't remember your handle/what thread...

Some updates...boiling temp sensor test came out to 250. I also measured the ohm resistance at ambient and it was pretty accurate with the chart. I'm willing to bet that initial jump on the needle I'm getting is the difference from it being accurate. Can someone please take a close picture with the resting position of the needle so I can compare? Another interesting thing, if I remove both the sender and oil pressure wires it only bounces to 120 from resting.
Also, sender p/n I had was 90164163200.

https://i.ibb.co/y8XrXST/20221013-172827.jpg

This is where I set mine at power off based on where others I know have their's set. I then confirmed the 212° measurement and it was accurate.

http://forums.pelicanparts.com/uploa...1665705342.jpg

This is an example from a different car (famoroso).

http://forums.pelicanparts.com/uploa...1665705478.jpg

Quote:

Originally Posted by 917_Langheck (Post 11821270)

Thank you....guess mine is right then

https://i.ibb.co/p0hZQPv/20221013-202702.jpg

Your sender is for a 76 and lower. Your gauge is inaccurate, but matches the sender, at least for the scale. Good news is that running at 250 means your running at 210 which is fine.

The temp gauge is a single module that fits into the larger assembly. You can remove that and see if the original face is below the white dial. If it is, then you can confirm if it is the same type - not a 340° gauge, and not an unnumbered scale gauge. The fact that there is a 40° difference suggests that the sender and the gauge maybe are not matched.

The other thing you can do is set the needle to 212 when the sender is at boiling, then reset the water to cold and track it as it comes up to boil and see if they rise in unison.

http://forums.pelicanparts.com/uploa...1665710128.jpg

Quote:

Originally Posted by 917_Langheck (Post 11820492)

Pull the sender out - put a plug into the case to minimize oil seep - and put it in a container of boiling water. With it wired to the car you can key on the car. It should read just above even with the 210° line.

http://forums.pelicanparts.com/uploa...1665624694.jpg

http://forums.pelicanparts.com/uploa...1665624732.jpg

http://forums.pelicanparts.com/uploa...1665624806.jpg

If it doesn't make that reading then the either the sender doesn't match the gauge, or the dial face is incorrect.

The above is a really inspired approach as it A) doesn't require R&Ring the gauge AND the sender like the below method. Also, it keeps the factory sender wiring in the test loop, unlike the conventional method below.

Bravo Richard!

Conventional testing method...

Quote:

Originally Posted by famoroso (Post 11788832)

Remove gauge. Remove sender. Put together a test rig to check 212° F with a pot of boiling water (or your significant other's Breville steamer). Apart from sending the gauge + sender to Palo Alto Speedometer, North Hollywood Speedometer, etc. and having them confirm the calibration, it's the only way to know for sure on YOUR gauge / sender combo.

http://forums.pelicanparts.com/uploa...1643799025.jpg

Alan Caldwell had an Upfixin' Der Porsche write-up on the procedure for a 914. It's pretty easy to do, especially if you have a 12VDC bench power source.

Check post #8 in this thread. It details the procedure...

http://forums.pelicanparts.com/porsche-914-914-6-technical-forum/206128-center-console-temp-gauge.html

Quote:

Originally Posted by famoroso (Post 11821694)

Thanks Frank! (the inspiration actually came by combining your original post and Jeff Higgins colman operation, so thanks to you both for that).

I like your method too, but didnt have access to such a fancy device such as your wife's....

Yours also reminds me a bit of this

http://forums.pelicanparts.com/uploa...1665773974.jpg

which is cool.

Just an update if anyone else has the problem. Ended it being the wrong sensor, I had the brass one, needed the later chrome one ( 911-606-112-00)

https://i.ibb.co/dMQ1Lvv/20221114-163812.jpg

Hey thanks for bringing closure to this.

Excellent result and I also appreciate the closure. :)

Quote:

Originally Posted by Djdiplomat (Post 11847159)

Just an update if anyone else has the problem. Ended it being the wrong sensor, I had the brass one, needed the later chrome one ( 911-606-112-00)

Thanks for closing the thread. But, yeh, the original sensor was "wrong" because someone swapped out the '77 numbered insert for a 74-76 one - which needs the "other" sensor.