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BMW Thermocouple Wiring Help

The thermocouple on my oil cooler needs to be replaced and I would like to put in the one made by BMW and supplied by our host.
My question is: how to wire the new thermocouple to the existing wires? I know it needs the spade connectors but what to do about where the ground and power wires are connected[?].
The oil cooler is out and this is my only sticking point.
As an aside, there has been some consternation expressed as to the difficulty in removing the oil cooler. The secret is to tilt the top of the cooler back [toward the rear of the car] and then lift it up and out-no grinding slots or cursing needed!
Thanks in advance for the help!
Drums

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Old 01-07-2007, 08:12 PM
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What color is the thermocouple wire? If it is a type J (Iron/Constantan) thermocouple, the thermocouple wire will be red and white (ANSI). Red is always the negative and White would be the positive. IEC uses black and white as their colors for type J TC's. I'm not sure if the lead wire pulled from the instrument is the same color as the TC wire, but you can determine polarity by looking at the TC itself.

The attached link shows all the various thermocouples, J, K, T, R, etc. so you should be able to tell what's in there now. Being a German car, the color code could very well follow IEC rather than ANSI but it should be pretty clear if you can access the TC.

One other quick item. TC's generate their own millivolt signal based on the dissimilar metals used. There is no power to them. You should just be dealing with a positive and negative DC voltage signal.

http://www.omega.com/toc_asp/frameset.html?book=Temperature&file=TC_GEN_SPECS_REF
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Last edited by autobonrun; 01-07-2007 at 08:29 PM..
Old 01-07-2007, 08:20 PM
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I don't think the item Pelican is going to send you is a thermocouple. It is probably a normal VDO thermal switch, just like the one used for radiator fans and oil coolers for VWs, BMWs, and Porsches.

Most likely the wiring Carreras normally use will work perfectly!
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Old 01-07-2007, 09:25 PM
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Quote:
Originally posted by Early_S_Man
I don't think the item Pelican is going to send you is a thermocouple. It is probably a normal VDO thermal switch, just like the one used for radiator fans and oil coolers for VWs, BMWs, and Porsches.

Most likely the wiring Carreras normally use will work perfectly!
Based on Warren's reply, my discussion of a TC is not applicable. A TC will give you an actual measurement of the temperature via an analog value. I thought you had verified it was a TC. If it is just a switch output, then the polarity should not matter.
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Old 01-07-2007, 09:44 PM
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There was a thread where the BMW part was used but nothing was said about how to wire it up.
Maybe I will PM the author of that thread.....
Drums
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Old 01-08-2007, 05:06 AM
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Quote:
Originally posted by drums

Drums

Just noticed your sig. greetings from one drummer to another
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Old 01-08-2007, 05:18 AM
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don't know if this helps, but my blue wire is the ground and is connected in the trunk. (labeled) It goes through he same grommet that the fog light wires went through. I used those water proff connectors that shrink with a heat gun. The brown (stock) wire connected to the other prong. I checked to make sure it was right before I tightened everything up. works like a champ but still hardly ever comes on. I used a blanket on th engine lid to check it. I think there's a procedure in the bentley to check operation also. Label the ground so that ten years from now you or someone else knows what that random wire is for.

Old 01-08-2007, 06:41 AM
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Thanks, Jerry!
Just pick a connection on the thermocouple and run with it, huh? The wire colors are the same in your '87 as they are in my early '89, which made this easier! Thanks again!

Hey FieroChris,
Have you looked at the list of my 'drivers'? No reinforcing rings, 'fast' sizes with 'Burnt Toast' Satin Oil Fade......
Drums

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Old 01-09-2007, 07:19 AM
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