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I wanted to r/r the coolant temp sensor and ordered one from AutohausAz. What I got was a three prong unit vs my two prong unit. The connector from my car does fit the two prong part of the new sensor. So, could I use this new sensor? Perhaps the third prong is for a temp switch?

I checked the continuity and found out two different values. Mine shows a resistance while the brand new unit shows open circuit.

thanks for any insight.

Here's the part I ordered: link
 

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I attempted to swap in a three prong onto my '90 300D, and it just made my aux fans run all the time the ignition was on. You'll want the correct two prong unit.
 

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The 3 prong is for the older M116 & M117 motor, its for the aux fan AND
a/c compressor lock out if the engine gets to hot.

As Casey said, get the correct part. Let me know if you need the part number.


Here it is, 008 542 4517

 

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Discussion Starter #4
The 3 prong is for the older M116 & M117 motor, its for the aux fan AND
a/c compressor lock out if the engine gets to hot.

As Casey said, get the correct part. Let me know if you need the part number.


Here it is, 008 542 4517

Ok, thank you for the info. Question is what do I do with this thing? Is it usable in the 103 engine?
 

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The 3 prong is for the older M116 & M117 motor, its for the aux fan AND
a/c compressor lock out if the engine gets to hot.

As Casey said, get the correct part. Let me know if you need the part number.


Here it is, 008 542 4517

Ok, thank you for the info. Question is what do I do with this thing? Is it usable in the 103 engine?
Return it to AutohausAz...it's not going to work in your car. If they won't take it back, then sell it here for a reduced amount....you'll lose a little, but not all.

Kevin
 

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3 prong was also used on the early 86/87 M103's and some M102's. 2 prong is 88 onwards. Simple mistake which AHAZ will fix. They have great customer support.
 

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Return it to AutohausAz...it's not going to work in your car. If they won't take it back, then sell it here for a reduced amount....you'll lose a little, but not all.

Kevin
Ok, will do. The 15% restocking fee shouldn't be a big deal. I'd rather exchange it out with the correct one.

Thanks.
 

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Discussion Starter #9
The 3 prong is for the older M116 & M117 motor, its for the aux fan AND
a/c compressor lock out if the engine gets to hot.

As Casey said, get the correct part. Let me know if you need the part number.
Here it is, 008 542 4517
According to the component picture on the attached pdf, the coolant temp sensor is toward the firewall. Correct me if I'm wrong but the two prong unit pictured above is a coolant switch and it matches the switch in the same location on my engine.

I need to pull the connector on the third switch near the firewall and see what it looks like.
 

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There's a coolant temp sensor for the CIS ECU which controls fuel mixture.

And there's a coolant sensor for the temp gauge.

Then there's the coolant switch for high speed aux fan.

That makes 3.

The blue switch is for the aux fan.

The switch at the rear should be for the CIS.
 

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Discussion Starter #11
There's a coolant temp sensor for the CIS ECU which controls fuel mixture.

And there's a coolant sensor for the temp gauge.

Then there's the coolant switch for high speed aux fan.

That makes 3.

The blue switch is for the aux fan.

The switch at the rear should be for the CIS.
Correct, the pdf did show the three items. I'm after the rear switch replacement as it can cause engine running issues. I need to pull the connector to see if it'll match my new sensor. I don't think it'll work but I'll check before returning it to the vendor.
 
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