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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old Yesterday, 07:25 PM
Cabover1000 Cabover1000 is online now
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Location: Belding,Michigan
 
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Mein Auto: 1999 bmw 528i
A few cooling system questions

1. what dose the temperature sensor in the lower radiator hose actully do.
2. Is the aux fan supposed to run when a/c is on ( it dosent). I know my aux fan I just got, works cause I replaced my upper radiator hose and got air in the line and the temperature rose and turned the fan on.
Thanks

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  #2  
Old Yesterday, 07:43 PM
Wgosma Wgosma is online now
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The aux fan MAY run when the a/c is engaged, but not necessairly 100% of the time as I recall; it's dependant on the load on the cooling system, pressure in the system, etc. If system pressure gets too high for example, i.e. the system is running too hot then there is sensor that will detect this and cut off power to a/c; i.e. the a/c will stop working until the pressure is below specified max value.
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  #3  
Old Yesterday, 09:02 PM
edjack edjack is offline
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One way the fan is commanded on is when the A/C system pressure goes beyond the set point. It does not, AFAIK, shut down the A/C. There may very well be a pressure point that does shut it down.
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  #4  
Old Yesterday, 10:15 PM
Wgosma Wgosma is online now
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Hi Ed
There is a 'high' pressure set point that when reached will turn off/disengage the compressor so as to not damage the system....when my cars aux fan failed the a/c would run intermittently, I.e. When the system got too hot and pressure went above high set point the a/c unit was shut down.


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  #5  
Old Yesterday, 11:59 PM
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bluebee bluebee is offline
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Quote:
Originally Posted by Cabover1000 View Post
1. what dose the temperature sensor in the lower radiator hose actully do
It's not a temperature sensor...
- How does the cooling system work anyway (1)
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Each repair should invariably add to our knowledge base by the process of inexorable incrementalism.
Your job, in return, is to read the suggested threads, where the best people will always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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  #6  
Old Today, 01:37 AM
Cabover1000 Cabover1000 is online now
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Quote:
Originally Posted by bluebee View Post
It's not a temperature sensor...
- How does the cooling system work anyway (1)
The first picture in the The link you supplied says its a temperature sensor.

Thanks everyone for your posts and information!

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