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  #1  
Old 05-11-2012, 04:51 PM
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AC temp switch

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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  #2  
Old 05-11-2012, 04:57 PM
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Is the switch currently out of the car? If not, is your a/c system charged?
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Old 05-11-2012, 05:29 PM
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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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Old 05-11-2012, 05:59 PM
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Quote:
Originally Posted by tangofox007 View Post
Is the switch currently out of the car? If not, is your a/c system charged?
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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  #5  
Old 05-11-2012, 06:32 PM
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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.

Quote:
Originally Posted by WDBCB20 View Post
The one in the car I assume not to be working because the fan never comes on.
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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Old 05-11-2012, 07:00 PM
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Originally Posted by tangofox007 View Post
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. will try that

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. Correct. DAMHIK (don't ask me how I know) Wanted to do a quick swap when I started to hear the telltale hiss upon starting to remove it.


That is a very common sign of low refrigerant. Had the issue with full refrigerant. Though its almost empty now. Maybe try a hair dryer or heat gun on the in-car switch. Would that work despite low refrigerant?
Will report back.
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Old 05-11-2012, 07:09 PM
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the aux fan temp switch can be removed from the charged system. the pressure switch can not.
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Old 05-11-2012, 08:13 PM
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Quote:
Originally Posted by Phillytwotank View Post
the aux fan temp switch can be removed from the charged system. the pressure switch can not.
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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Old 05-11-2012, 08:18 PM
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Originally Posted by Phillytwotank View Post
the aux fan temp switch can be removed from the charged system. the pressure switch can not.
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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Old 05-11-2012, 08:19 PM
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Quote:
Originally Posted by WDBCB20 View Post
Will report back.
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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  #11  
Old 05-11-2012, 08:20 PM
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Quote:
Originally Posted by WDBCB20 View Post
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.
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.

Quote:
Originally Posted by WDBCB20 View Post
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.
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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Old 05-11-2012, 08:30 PM
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Quote:
Originally Posted by tangofox007 View Post
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. LOL, you just confirmed the edit i added to my post#9. Our posts must have crossed.



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.
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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Old 05-11-2012, 08:32 PM
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Quote:
Originally Posted by WDBCB20 View Post
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?
None that I could envision.
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