High Idle on my '85 380sl

[Richard Wooldridge]

I believe that sensor with the brown wire is the one that keeps the heater from operating until the engine reaches a warm temperature. I don't have any documentation to support this, but I remember reading it somewhere.

[donbryce]

Originally Posted by BabyBlueBenz

'Tis true.

Good thread on subject at 560SL diagnostic port/tool.

Alas, my '86 560SL is not equipped with the advanced blinkernator technology.

I will have to determine the proper function of my CIS-E input sensors the hard way.

If by the 'hard way', you are referencing that 'duty cycle' business, please, please share with us how the test for B11/2 is performed. I'm in the same boat, no diagnostic port for a code reader, and I've tried before with no success to understand and apply that 'duty cycle' thing (even if I had a multimeter with the duty cyle function on it, which I don't). And that B11/2 sensor is the most expensive of the three that sense water temperature too, nearly $100.00 for me in Canada, so I won't be just replacing it 'on principal'!

[BabyBlueBenz]

Originally Posted by Richard Wooldridge

I believe that sensor with the brown wire is the one that keeps the heater from operating until the engine reaches a warm temperature. I don't have any documentation to support this, but I remember reading it somewhere.

You are correct, Sir!

Meet "S71", the Cold Engine Lock-out Switch:

[BabyBlueBenz]

Originally Posted by donbryce

If by the 'hard way', you are referencing that 'duty cycle' business, please, please share with us how the test for B11/2 is performed. I'm in the same boat, no diagnostic port for a code reader, and I've tried before with no success to understand and apply that 'duty cycle' thing (even if I had a multimeter with the duty cyle function on it, which I don't). And that B11/2 sensor is the most expensive of the three that sense water temperature too, nearly $100.00 for me in Canada, so I won't be just replacing it 'on principal'!

Well, I've decided to invest in a new multimeter with the Duty Cycle function. Here's what I intend to purchase: an OTC Stinger 35 Series Meter at http://www.sears.com/shc/s/p_10153_12605_00970905000P for $66.99. Based on my retesting of the Idle Speed Control Unit this afternoon, it appears that I need to interact with the CIS-E Control Unit. I tried to make do with my Dwell meter, but the conversion formula is too confusing. Check out http://www.automotivehelper.com/topic607279.htm and http://www.allpar.com/fix/fixcarb.html for explanations on the differences between Dwell and Duty Cycle.

I'll be starting a new thread detailing today's experience testing the ISCU according to the MB service manual, which sidetracks into testing ol' B11/2 Coolant Temperature Sensor/Sender for CIS-E & EZL.