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126: 1981 300SD, 1987 300SDL
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119 Posts
Discussion Starter #1 (Edited)
So I pulled my existing switch off the receiver/drier and tested by the manual's 55-65 degrees Celsius which is about 150 Fahrenheit.

For readings, I used an infra-red thermometer (above 150 F) and a multimeter (above 65 C) to check the temp of the water and switch on the metal and red plastic, but never got any continuity on the leads, just inifinite resistance.

Just got a new Behr/Hella one and same thing.

Has anyone ever successfully tested one of these switches and got continuity?
 

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560SEC, 190E, Frontier, 240Z
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1,329 Posts
What part of town are you in?
We can test the same part on my car and compare real time?

I am in the Deer Valley area at my office all day tomorrow.

Tj
 

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'82 Euro 500SEL, '85 Euro 500SEC AMG WB Cabriolet,'86 Euro 500SEC RUF
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9,487 Posts
Do you know if it is a normally open or normally closed switch? if normally open, then I think there would be no continuity between the connections. JAWAG!
 

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126: 1981 300SD, 1987 300SDL
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119 Posts
Discussion Starter #5 (Edited)
Do you know if it is a normally open or normally closed switch? if normally open, then I think there would be no continuity between the connections. JAWAG!
My understanding is that it's normally open because it only closes to turn on the fan above 77 degrees Celcius (170.6 Fahrenheit) according to the manual when you add the tolerances to the top cut-in temp. Based on this, I'd expect that when the unit temp got above the 80s Celcius range, the leads would drop or show less than infinite resistance. That never happened.

The manual mentions turning the aux fan on and off based on the water bath, but not testing with a multimeter. Maybe the test requires an applied 12v voltage?

What does JAWAG mean?

Just A Wild A$$ Guess?
or
Just Another Whiteguywith an Asian Girlfriend?

LOL!
 

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Registered
126: 1981 300SD, 1987 300SDL
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119 Posts
Discussion Starter #6
What part of town are you in?
We can test the same part on my car and compare real time?

I am in the Deer Valley area at my office all day tomorrow.

Tj
D'oh! I just saw your post at the end of the day. Thanks for the kind offer. I was about to give up on responses today and just install everything since the system's been flushed. The receiver dryer was going to be the last thing to put in and only after making sure this new switch worked. At this point I was going to just install it and if it didn't actually work (if everything else works this time), I'd short the fan (so the key-on runs it) or connect it in parallel with the clutch so it runs when the AC system is on.

The manual says you can replace the temp switch with the system filled, but looking at my two old dryers, I'm not so sure about that. Do you have one that you know works, or are you in the same position wanting to know if your existing or new one will pass this test while your AC system awaits assembly?
 

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'82 Euro 500SEL, '85 Euro 500SEC AMG WB Cabriolet,'86 Euro 500SEC RUF
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Just a Wild Assed Guess...
The time valve works on this same general arrangement. Closes at temp. and that completes the ground.
 

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'82 Euro 500SEL, '85 Euro 500SEC AMG WB Cabriolet,'86 Euro 500SEC RUF
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Time valve activates the cold start valve on warm start up. Cold start up , contrary to popular belief, works every time you start the car, overnight, etc. Makes no difference warm or cold weather. On warm start the time valve operates the Cold Start valve For just a few seconds. Cold start(overnight, etc) it is operated as long as you are turning the car over. If the time vave goes bad you have hard warm starts.
 

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126: 1981 300SD, 1987 300SDL
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119 Posts
Discussion Starter #10
What model car is this on and where is it located? Is it a valve for coolant, fuel, ...?
 

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'82 Euro 500SEL, '85 Euro 500SEC AMG WB Cabriolet,'86 Euro 500SEC RUF
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Probably on the gassers only, but I don't know for sure. I know it has been on my 380SE, 500SEL and all my SEC;s. It is in the intake manifold. Water temperature activates it.
Sorry for taking it off topic.
 

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126: 1981 300SD, 1987 300SDL
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119 Posts
Discussion Starter #12
Probably on the gassers only, but I don't know for sure. I know it has been on my 380SE, 500SEL and all my SEC;s. It is in the intake manifold. Water temperature activates it.
Sorry for taking it off topic.
I'm sure gassers only. I've only dealt with the 300SDs since I have two and only spend time working on one right now.

I'll take it back on topic. My Temperature switch for the aux fan that is installed on the receiver/dryer (I almost called it the deceiver/liar), well:

IT WORKS!

How do I know? I installed it and after getting my AC working, and connecting it, it actually closed the circuit and kept the fan running. Whoo hoo! So much for the manual's instructions of saying to immerse the thing in water and removing it with the AC system filled. bah. I looked at my old receiver/dryer and removing the temp switch, would open the AC system, exposing it to the air, destroying the vacuum, or outgassing refrigerant. hah. so much for following that manual.

There are a few youtube videos that show the internal workings of the receiver/dryer/accumulator and how it pretty much from the side takes in refrigerant mix, filters it through a grate, filter, dessicant, filter, grate, out the bottom, and sucks it up through a tube in the center to the top port, where the temp switch is.

If the temp switch turned out not to work, I was planning to just use the AC clutch wires to trigger a relay for the wires to the temp switch and bypass it.
 
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