Is there any way to test these out of the car? This is the switch mounted on the drier which tells the aux fan when to run.

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'83 SD, 2x '85 SD
You are entitled to your own opinions, you are not entitled to your own facts.

Is the switch currently out of the car? If not, is your a/c system charged?

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

I can't speak for your SD, sorry, but my cars use a pressure switch to turn on the auxiliary fan(s) in low speed. The trip point is ON at 16 bar (232 psi) and OFF at 12 bar (174 psi). To test that outside the car would require some kind of pressure-generating rig that would be compatible with refrigerating fluids, since the test rig would contaminate the switch in a small way. You might even be able to use a modified pop tester for injectors.

If your car uses a temperature switch then I am out to lunch.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

I want to test a second used one that I have. The one in the car I assume not to be working because the fan never comes on. Fan works fine when shorting terminals leading to switch.

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'83 SD, 2x '85 SD
You are entitled to your own opinions, you are not entitled to your own facts.

You should have no continuity thru the switch at room temperature. If you put the switch in a pot of warming water on the stove, the switch should close at around 125*F.

If that is the exact switch that you have, keep in mind that you will loose your refrigerant if you remove it from the r/d.

That is a very common sign of low refrigerant. Maybe try a hair dryer or heat gun on the in-car switch.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

Will report back.

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'83 SD, 2x '85 SD
You are entitled to your own opinions, you are not entitled to your own facts.

the aux fan temp switch can be removed from the charged system. the pressure switch can not.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

I must have been completely mistaken in thinking that there were two different types of temp switches!!! And I was so sure that I knew what I was talking about. Thanks for setting me straight.

Just one question: Did you read post #6? (With special reference to the part about the telltale hiss.)

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

That's what i first concluded from readings on the web, yet the hiss of escaping refrigerant suggested otherwise. Unless there's a valve type mechanism on the r/d that engages once the switch has been screwed out far enough. Or the AC shop slapped in some cheapo aftermarket r/d which has no barrier between switch and refrigerant.

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'83 SD, 2x '85 SD
You are entitled to your own opinions, you are not entitled to your own facts.

Could not get continuity at + 125F. Also no luck with the one on the car though less conclusive - can't be sure I'm getting it hot enough.

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'83 SD, 2x '85 SD
You are entitled to your own opinions, you are not entitled to your own facts.

There are two types of temp switches. One connects through to the refrigerant and one does not. (Some aftermarket receiver/driers have ports that will accomodate either version.) We both know which version you have.

On my '82 300D, engine compartment heat, on a really hot day, will occasionally trip my switch, even with the a/c not in operation.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

It would just be annoying if it'll still not work after putting in a new one. Could there be an issue with the dryer?

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'83 SD, 2x '85 SD
You are entitled to your own opinions, you are not entitled to your own facts.

None that I could envision.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.